NASA/TP-2001-209979
InternationalVLBI Servicefor GeodesyandAstrometry
2000 ANNUALREPORT Editedby N.R. Vandenberg and K.D. Baver
IVSCoordinating Center February2001
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On the cover: The cover layout includes a photograph of the 32-m VI.BI antenna at Tsukuba, Japan, operated by the Geographical Survey Institute
NASAITP-2001-209979
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internationalVLBIServicefor GeodesyandAstrome_ry
2000 ANNUALREPORT Editedby nberg N.R. Vande and
K.D.
BaYer
IVSCoordinating Center February2001
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/
Preface
This volume of reports and Astrometry tional geodetic The
IVS
is the 2000 Annual
Report
of the International
VLBI
Service
for Geodesy
(IVS). The individual reports were contributed by VLBI groups in the internaand astrometric community who constitute the permanent components of IVS. 2000
Annual
Report
documents
the
work
of the
IVS components
for the period 31, 2000. The reports
March 1, 1999 (the official inauguration date of IVS) through December document changes, activities, and progress of the IVS. The entire contents of this Annual Report also appear on the IVS web site at http ://ivscc. This book
and the web site are organized
• The first section contains components, information Chair. • The
gsf c. nasa. gov/publicat ions/ar2000
second
section
on GPS phase the International
as follows:
general information about the Directing
of Special
center mapping, Astronomical
Reports
about IVS, a map showing the location of the Board members, and the report of the IVS
contains
a status
report
of the IVS Working
Group
a reproduction of the resolution making IVS a Service of Union (IAU), and a reprint of the VLBI Standard Interface
(VSI). • The
next
seven
sections
tions, Operation Centers, velopment Centers. • Tile last section of Member and IVS components,
have
includes
hold the component Correlators,
reference
Data
information
Affiliated organizations, the list of institutions
The 2000 Annual Report demonstrates made during our first 22 months.
reports Centers,
about
from the Analysis
Coordinators, Centers,
IVS: tile Terms
Network
Sta-
and Technology
De-
of Reference,
the lists
the IVS Associate Member list, a complete list of contributing to this report, and a list of acronyms.
the vitality
nl
of the IVS and the outstanding
progress
we
Table
Preface About IVS IVS IVS IVS
of Contents
............................................................................................... IVS
iii
..........................................................................
1 -/
Organization ..................................................................................... Component Map .................................................................................. Directing Board .................................................................................. Chair's Report ....................................................................................
Special
Reports
IVS/IGS/ILRS IAU Resolution VLBI Standard IVS
....................................................................
Working Group on GPS Phase Center Mapping ...................................... (IVS is a Service of the IAU) ......................................................... Interface Specification ................................................................
Coordination
.................................................................
Coordinating Center Report ........................................................................... Analysis Coordinator Report ......................................................................... Network Coordinator Report ......................................................................... Technology Coordinator Report ...................................................................... Network
Stations
..................................................................
Algonquin Radio Observatory . ....................................................................... 2000 Activities Report of Fortaleza Station ........................................................... Gihnore Creek Geophysical Observatory .............................................................. God(lard Geophysical and Astronomical Observatory . ................................................ Hartebeesthoek Radio Astronomy Observatory (HartRAO) ........................................... Kashima 34m Radio Telescope ....................................................................... Key Stone Project VLBI Stations (Kashima, Koganei, Miura, and Tateyama) ......................... Kokee Park Geophysical Observatory ................................................................. Matera CGS VLBI Station ...........................................................................
2 4 6 8 11 13 17 18 51 53 55 65 67 71 73 77 78 81 84 88 92 95 98
Medicina Station Report ............................................................................ Report from the Noto VLBI Station ................................................................. NYAL Ny-Mesund 20 Metre Antenna ............................................................... German Antarctic Receiving Station O'Higgins ...................................................... The IVS Network Station Onsala Space Observatory ................................................ Seshan VLBI Station Report ......................................................................... Simeiz Station: Geodetical Experiments and Single Dish Observations ............................... Svetloe Radio Astronomical Observatory . ........................................................... JARE Syowa Station 11-m Antenna, Antarctica ..................................................... Transportable Integrated Geodetic Observatory . .................................................... Tsukuba 32-m VLBI Station ........................................................................
102 104 106 110 113 117 120 123 127 131 135
Nanshan VLBI Station Report ...................................................................... "_Vestford Antenna ..................................................................................
139 141
Station Report of the 20m Radiotelescope at Wettzell ............................................... Observatorio Astrondmico Nacional .................................................................
145 149
_(Mlowknife
153
Observatory
. ...........................................................................
v
Operation
Centers
...............................................................
155
The Bonn Geodetic VLBI Operation Center ......................................................... CORE Operation Center Report .................................................................... U.S. Naval Observatory Operation Center ...........................................................
157 159 163
Correlators ....................................................................... The Bonn Astro/Geo Mark IV Correlator ........................................................... Haystack Observatory VLBI Correlator ............................................................. KSP-VLBI Correlation Center Report ............................................................... Tsukuba VLBI Center .............................................................................. Washington Correlator ..............................................................................
165 167 170 173 176 178
Data BKG
181 183
Centers Data Center
..................................................................... ..................................................................................
Data Center at Communications Research Laboratory ............................................... CDDIS Data Center Report ......................................................................... Italy CNR Data Center Report ..................................................................... Paris Observatory (OPAR) Data Center ............................................................. Analysis
Centers
185 188 192 194
.................................................................
Analysis Center of Saint-Petersburg University ...................................................... Bordeaux Observatory Analysis Center Report ...................................................... Matera CGS VLBI Analysis Center ................................................................. Analysis Center at Communications Research Laboratory ........................................... DGFI Analysis Center Annual Report 2000 ......................................................... Combination of VLBI, GPS and SLR Data Analysis at FFI ......................................... The GIUB/BKG VLBI Analysis Center ............................................................. GSFC VLBI Analysis Center ........................................................................ Analysis and Research at the Haystack Observatory . ................................................ IAA VLBI Analysis Center Report for 2000 ......................................................... Italy CNR Analysis Center Report .................................................................. Vienna IGG Special Analysis Center Annual Report 2000 ........................................... Paris Observatory Analysis Center OPAR: Report on Activities, March 1999 - December The IVS Special Analysis Center at tile Onsala Space Observatory . ................................. Analysis Center Report from Shanghai Astronomical Observatory for 1999.03 2000.12 USNO Analysis Center for Source Structure Report ................................................. Technology Development Centers .............................................. Canadian VLBI Technology Development Center .................................................... Technology Development Center at CRL ............................................................ Combination of VLBI, GPS and SLR Software Development at FFI ................................. GSFC IVS Technology Development Center Report ................................................. Haystack Observatory Technology Development Center .............................................. Institute of Applied Astronomy Technology Development Center .................................... Technology Development at IEEC ................................................................... The IVS Technology Development Center at the Onsala Space Observatory ..........................
vi
197
2000 ..............
.......
199 203 207 210 215 218 221 225 229 232 236 238 241 245 249 253 257 259 263 267 269 273 277 279 283
IVS Information .................................................................. IVSTermsofReference ............................................................................. IVSMemberOrganizations ......................................................................... IVSAffiliatedOrganizations ........................................................................ IVSAssociate Members............................................................................. IVSPermanent Components ........................................................................ Addresses
of Institutions
List of Acronyms
Contributing
to this Report
................................................
....................................................................................
vii
287 289 299 300 301 312 316 321
..
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.
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t
OBJECTIVES
REALIZATIONAND STATUSOF IVS
IVS is an international collaboration of organizations which operate or support Very Long Baseline Interferometry (VLBI) components. The goals are:
IVSconsistsof •
30 Network Stations, acquiring high performance VLBI data, 3 Operation Centers, coordinating the activities of a network of Network Stations, 6 Correlators, processing the acquired data, providing feedback to the stations and providing processed data to analysts, 6 Data Centers, distributing products to users, providing storage and archiving functions, 20 Analysis Centers, analyzing the data and producing the results and products, 8 Technology Development Centers, developing new VLBI technology, 1 Coordinating Center, coordinating daily and long term activities.
• 1. To provide a service to support geodetic, geophysical and astrometric research and operational activities.
•
2. To promote research and development activities in all aspects of the geodetic and astrometric VLBI technique. 3. To interact with the community of users of VLBI products and to integrate VLBI into a global Earth observing system.
• • • •
The IVS •
• • • • • •
Interacts closely with the IERS,which is tasked by IAU and IUGG with maintaining the international celestial and terrestrial reference frames (tCRF and ITRF), coordinates VLBI observing programs, sets performance standards for the observing stations, establishes conventions for data formats and products, issues recommendations for analysis software, sets standards for analysis documentation, institutes appropriate product delivery methods in order to insure suitable product quality and timeliness.
Altogether •
74 Permanent Components, representing 31 institutions in t5 countries, 250 Associate Members.
•
in addltlen the IVShas: •
Directing Board, determining policies, standards and goals; the board is composed of 14 members (elected and ex officio), including Coordinators for the network, analysis and technology.
•
IVS STRUCTURE
U_S
J
8s
I !
I
IVS MEMBER ORGANIZATIONS
IVS AFFILIATEDORGANIZATIONS
The following organizations contribute to IVS by supporting one or more IVS components. They are considered IVS Members. Listed alphabetically by country.
The following organizations cooperate with IVS on issues of common interest, but do not support an IVS component. Affiliated Organizations express an interest in establishing and maintaining a strong working association with IVS to mutual benefit. Listed alphabetically by country.
_:_
_ _-
.....
_::
Vienna University of Technology Centro de R6dio Astronomia e
Austria
Aplica?_es Espaciais Space Geodynamics Laboratory Geodetic Survey Division, Natural Resources Canada Dominion Radio Astrophysical Observatory Canadian Space Agency Chinese Academy of Sciences Observatoire de Paris Observatoire de Bordeaux Deutsches Geod_tisches
Brazil Canada
Forschungsinstitut Bundesamt for Kartographie und Geod_sie Geodetic Institute of the University of Bonn Istituto di Radioastronomia CNR
Germany
Agenzia Spaziale Italiana Geographical Survey Institute Communications Research Laboratory National Astronomical Observatory of Japan National Institute of Polar Research Norwegian Defence Research Establishment
Italy Japan Japan
Norwegian Mapping Authority Astronomical Institute of St.-Petersburg University Institute of Applied Astronomy Hartebeesthoek Radio As!ronomy Observator_ Institut d'Estudis Espacials de Catalunya Instituto Geografico Nacional Chalmers University of Technology National Academy of Sciences, Kiev Laboratory of Radioastronomy of Crimean Astrophysical Observatory NASA Goddard Space Flight Center U. S. Naval Observatory Jet Propulsion Laboratory
Canada Canada Canada China France France
Australian National University University of New Brunswick Max-Planck-lnstitut for Radioastronomie FOMI Satellite Geodetic Observatory Joint Institute for VLBI in Europe (JIVE) Westerbork Observatory National Radio Astronomy Observatory
Australia Canada Germany Hungary Netherlands Netherlands USA
PRODUCTS
Germany Germany Italy
Japan Japan Norway Norway Russia Russia South Africa Spain Spain Sweden Ukraine Ukraine USA USA USA
TheVLBItechnique contributesuniquely to • Definition and realization of the international Celestial Reference Frame (ICRF) • Monitoring of Universal Time (UT1) and length of day (LOD) • Monitoring the coordinates of the celestial pole (nutation and precession) Furthersignificant productsare • All components of Earth Orientation Parameters at regular intervals • Station coordinates and velocity vectors for the realization and maintenance of the International Terrestrial Reference Frame (ITRF)
All VLBIdata and resultsin appropriate formats are archived in data centers and publicly available for research in related areas of geodesy, geophysics and astrometry.
http://ivscc.gsfc.nasa.gov
IVS COMPONENTSBY COUNTRY Austria
1
Brazil
1
Canada
3
China
3
France
3
Germany
8
Italy
7
Japan
14
Norway Russia
3 5
South Africa
1
Spain Sweden
2 3
Ukraine
2
USA
18
Total
74
A complete list of IVS Permanent Components is in the IVS Information section of this volume.
_'_ Network Station O Operation Center O Correlator Date Center Anelyeis $_
:_
Center
Technology Coordinating
Development Center
Center
_
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_ Hartebeesthoek
§
NAME:WolfgangSchl6ter AFFILIATION: Bundesamt fiJr Kartographie undGeodiisie, Germany POSITION:ChairandNetworks Representative TERM:Feb1999 to Feb2003
NAME:JamesCampbell
NAME:EdHimwich
AFFILIATION: Universityof Bonn, Germany
AFFILIATION: NVI, Inc./Goddard SpaceFlightCenter,USA
POSITION:lAGRepresentative
POSITION:NetworkCoordinator
TERM:ex officio
TERM:permanent
NAME:WayneCannon
NAME:KerryKingham
IU:FIUIi11ON: Space Geodetic Laboratory, Canada
AFFILIATION: U.S.NavalObservatory, USA
POSITION:At LargeMember
POSITION:Correlators andOperation Centers Representative
TERM:Feb1999 to Feb2001 TERM:Sep2000 to Feb2003
NAME:NicoleCapitaine
NAME:TetsuroKondo
AFfiLIATION: ParisObservatory, France
AFFILIATION: Communications
POSITION:IAURepresentative
POSITION:Technology Development CentersRepresentative
Research Laboratory, Japan
TERM:ex officio TERM:Feb1999 to Feb2001
NAME: Chopo Ma
NAME: Nancy Vandenberg
AFFILIATION: NASA Goddard Space Flight Center, USA
AFFILIATION: NVI,Inc./Goddard Space Flight Center, USA
POSITION: IERS Representative andAnalysis andDataCenters Representative
POSITION: Coordinating Center Director TERM: exofficio
TERM: exofficio
NAME: Shigeru Matsuzaka
NAME: Alan Whitney
AFFILIATION: Geographical Survey Institute, Japan
AFFILIATION: Haystack Observatory, USA
POSITION: Networks Representative
POSITION: Technology Coordinator
TERM: Feb1999toFeb2003
TERM: permanent
NAME: AxelNothnagel AFFILIATION: University ofBonn, Germany POSITION:Analysis Coordinator TERM:permanent
NAME:PaoloTamasi AFFILIATION: CNRBologna, italy POSITION:At LargeMember TERM:Feb1999 to Feb2003
WeUgang ScblJter Bundesamt fOrKartegraphie undGeodtsle iNTRODUCTiON This is the second issue of the Annual Report of the International VLBI Service for Geodesy and Astrometry. It is a very good documentation of our activities. The Annual Report demonstrates the vitality of the IVS. With the 1999 Annual Report - released before the end of 1999 - emphasis was placed on documenting the status of the individual components. The 2000 Annual Report documents changes, activities and progress of the Service. I'm personally proud about the progress and the results and also about the reliability of the IVS Associate Members, that we can issue the Annual Report 2000 in such a timely manner. Let me express my thanks to all who have contributed.
EVENTSDURING 2000 The first IVS General Meeting was held February 21 to 24, 2000, with more than 120 participants, representing mostly all components of the IVS. The purpose of the IVS 2000 General Meeting was to share information and to plan future activities. One of the goals was to strengthen our cooperation and to build bridges be_een the various components for a better understanding. These goals were considered by the program committee. Tutorials were held in order to introduce the session topic to those who work in different areas. I thank the members of the program committee: Marshall Eubanks/USNO, Hayo Hase/BKG, Ed Himwich/NVI, Inc./GSFC, Yasuhiro Koyama/CRL, Chopo Ma/NASA GSFC, Arthur Niell/MIT Haystack, Axel Nothnagel/GIUB, Hans Peter Plag/SK, Rich Strand/GCGO, Nancy Vandenberg/NVI, Inc./GSFC, and Alan Whitney/MIT Haystack. The Proceedings of the IVS 2000 General Meeting were released by the editors Nancy Vandenberg and Karen Baver in August. The papers are electronically available as well as in book form. The publication with the tutorials is a valuable contribution not only to VLBI experts and participants, but also to people who have an interest in learning about VLBI. During the IVS 2000 General Meeting, a first meeting was held of the IVS Working Group on "GPS phase center mapping", which is a joint Working Group with the International GPS Service (IGS) and International Laser Ranging Service (ILRS).The objectives were "to
study the feasibility of equipment, time required, and if it could be done with accuracy sufficient to make it worthwhile". The members of the WG are Brian Corey/MIT Haystack and Ed Himwich/NVI, Inc./GSFC for the IVS, Tom Herring/MIT Boston and Tim Springer/AIUB for the IGS, and Graham Appleby/UK and Richard Biancale/ CNES for the ILRS.I thank the members for their contribution. The activity and the status of the work can be seen on the IVS home page http://ivscc.gsfc.nasa.gov. A status report is given in this Annual Report. On the last day of the 2000 General Meeting, February 24, the first IVS Analysis Workshop was held. The Analysis Coordinator Axel Nothnagel, who became the Analysis Coordinator on October 1, 1999, organized and chaired the meeting. Standards, analysis models, and contributions of the various Analysis Centers were discussed. Five working groups were established in order to share the workload. Access to all the information is made available also via http://ivscc.gsfc.nasa.gov and the home page of the Analysis Coordinator, which is linked from the IVS home page. In September 2000 the hardware VLBI Standard Interface (VSI-H) specification was released. The complete specification is reprinted in this Annual Report. The VSI-H specification was developed by an international committee of experts in VLBI instrumentation, led by Alan Whitney/MIT Haystack, the IVS Technology Coordinator, in a concerted effort to standardize interfaces to/from VLBI data recording and playback systems. Adherence to the VSI-H specification will allow data collected on heterogeneous VLBI data systems to be processed directly on VLBI correlators. A standardized software interface, VSI-S, is expected to follow within the next year. I would like to express my thanks to the committee especially Alan Whitney/MIT Haystack-USA as the chair, Wayne Cannon and Richard Worsfold/CRESTechCanada, Ralph Spencer/Jodrell Bank Observatory-UK, Richard Ferris/CSIRO Telescope National FacilityAustralia, John Romney, George Peck/NRAO-USA, Brent Carlson/Herzberg Institut of Astrophysics NRCCCanada, Tetsuro Kondo, Junichi Nakajima, Yasuhiro Koyama, Mamorou Sekido and Hitoshi Kiuchi/CRLJapan and Mickael Popov/Astro Space Center of Lebedev Physical Institute Moscow-Russia.
NEW IVS MEMBERS During 2000 IVS received proposals from two institutions applying to become IVS components. In January 2000 the Directing Board accepted the proposal from the U.S.
NavalObservatory to contribute with the "USNO Analysis Center for Source Structure" and in December 2000 the Directing Board accepted the proposal from the Institut fiJr GeodLisie und Geophysik of the Technical University Vienna to contribute with an Associate Analysis Center based on OCCAM with special emphasis on modeling the tropospheric refraction. I thank both agencies for their willingness to cooperate with the IVS. Their important contributions are appreciated very much. The Directing Board changed the Termsof References in order to extend the IVS membership to affiliated organizations. The affiliated organizations do not necessarily support an IVS component but expressed their willingness to cooperate with IVS on issues of common interest. The Directing Board accepted proposals from the following: Geodynamics Group, Research School of Earth Science, Canberra/Aust[.alia; Westerbork Observatory, Dwingeloo/ Netherlands; FOMI Satellite Geodetic Observatory, Budapest/Hungary; Department of Geodesy and Geomatics Engineering of the University New Brunswick/ Canada; National Radio Astronomy Observatory (NRAO), Socorro/USA; Max Planck Institute fLir Radioastronomie, Bonn/Germany. The Joint Institute for VLBI in Europe, Dwingeloo/Netherlands changed their membership category to that of an Affiliated Member. I thank the Affiliated Member organisations for their interest and for their willingness to cooperate with IVS.
DIRECTING BOARD The IVS Directing Board held its 3rd and 4th meetings in 2000. The 3rd Meeting was held in Wettzell on February 20, 2000, the day before the IVS 2000 General Meeting. The 4th meeting was held in Paris/France on September 17, 2000. Detailed information about the meetings was mailed to the Associate Members through the ivsmail, and it is also available at http://ivscc.gsfc.nasa.gov. We have had some personnel changes in 2000. Marshall Eubanks has withdrawn from the IVS Directing Board due to personal reasons. His successor as the representative for the Correlators and Operation Centers is Kerry Kingham, USNO. On behalf of the IVS I would like to thank Marshall for all he has done for the IVS and for the entire VLBI community especially in the field of data analysis and investigations in Earth orientation. We wish him success for his new business.
The terms of the representatives of the Analysis Centers and of the Technology Development Centers were two years, ending with the board meeting in February 2001. The election, conducted by the election committee, which included Shigeru Matsuzaka/Japan as chair, Paolo Tomasi/ttaly and Nancy Vandenberg/USA, resulted in the election of Harald Schuh, TU-Vienna/Austria as the representative for the Analysis Centers and of Arthur Niell from Haystack Observatory/USA as the representative of the Technology Development Centers. Also one of the At Large positions ends after two years. The Directing Board elected Yasuhiro Koyama from CRL/Japan. Congratulations to all new elected board members. I take the opportunity to thank Tetsuro Kondo and Wayne Cannon for their contributions and their fruitful discussions during the first two years term. I'm sure both will continue to support the IVS.
IVS IS A SERVICE OF THE IAU IVS has been recognized as a Service of the International Association of Geodesy (lAG) since July 1999 when the General Assembly was held in Birmingham/ England. Since the XXIVth General Assembly of the International Astronomical Union IAU held in Manchester/England, August 2000 the IVS is also recognized as a Service of the IAU. The fact of being an IAU Service will open up more cooperation with radio astronomy groups. You can find the IAU resolution reprinted in this Annual Report.
ACKNOWLEDGEMENTS The year 2000 has been a busy year for all of us. The activities summarized above indicate the vitality of our service. There is still a lot to do within the next years. We have to establish our products in order to realize what is expected from us as a service, we have to improve our observing programs and the analysis steps to provide and guarantee timeliness and highly reliable products. The discussion on these issues has started. I would like to express my gratitude to the IVS Coordinators Ed Himwich, Axel Nothnagel and Alan Whitney, who have to carry a heavy workload and responsibility. I thank Nancy Vandenberg for all the work she has done for the IVS as Coordinating Center Director such as organizing meetings, publishing proceedings, caring for the IVS homepage and much much more. I'm aware that every Associate Member supports IVS, so I will express my appreciation to all of you. Let's continue our good work.
9
_
m
m
k
2.o04..60
;, fg
MIT
Haystack
Technology
Observatory
IVS/IGS/ILRS
Working
Group
on
Brian
GPS
Phase
Development
Center
_/!
Center
Mapping
Corey
Abstract A joint the the
working
organization
1.
Accurate
for
composed
of representatives
VLBI observations antennas. This
of the working
Motivation
is essential
group
feasibility of using satellite transmitter
group,
and
establishing
knowledge
some
key points
working
of the location
in high-accuracy
from
the
IVS,
IGS,
of GPS satellites to measure report describes the motivation from
ILRS
is investigating
initial
of the
discussions.
group
of the phase center
GPS geodesy.
the
and
the phase center locations behind the investigation,
Estimates
of each GPS satellite
transmitter
of the scale of the terrestrial
antenna
reference
frame
(TRF) and of station zenith tropospheric delays are particularly sensitive to the phase center zcomponent, along the direction from the satellite toward the geocenter. A change of 1 meter in the assumed z-component for all satellites causes a change in the terrestrial scale of _8 ppb (50 mm in station height) and a change in zenith delay of _,-5 ram. Several related pieces of evidence point to significant errors
in the phase
center
locations
as-
sumed in most GPS geodetic analyses. The instantaneous location of each satellite is normally set equal to the vector sum of (1) the instantaneous position of the satellite center of mass, which is believed to be known to < 10 cm in all three dimensions from GPS orbital solutions and from SLR rangings on selected satellites, center of mass. When global GPS
and data
(2) the nominal offset between the phase center and the sets are analyzed with these phase center locations and
with absolute phase patterns for the GPS receiving to differ from the scale of the VLBI and SLR TRF's
antennas, the scale of the GPS TRF is found by _-,15 ppb, or 10 cm in station height [1, 2].
An adjustment of the z-component of the phase center offsets by 2 m brings the scale of the GPS TRF into agreement with VLBI and SLR. Furthermore, if the phase center z-component offsets are estimated from the GPS data, differences from the nominal offsets of 1 2 m are found [1, 2]. The
immediate
on GPS phase at the Scripps
impetus
for the
formation
center mapping was a series Institution of Oceanography
of the
IVS/IGS/ILRS
joint
working
of discussions at the IGS Analysis in 1999 regarding the uncertainty
group
Center in the
(WG)
Workshop location of
the phase centers of the GPS satellite transmitters. It was suggested at the workshop that VLBI observations of the satellites could provide independent information on the phase center locations, including perhaps the relative locations for the 12 individual radiating elements in the phased array transmitters. An informal request was made to the IVS to lead an investigation of the feasibility of such observations.
2.
Establishment
and
At the second
organization
IVS Directing
Board
of working meeting
in July
group 1999, the board
decided
to establish
a
working group on this matter and to invite the IVS, IGS, and ILRS chairs to nominate representatives to serve on it. The charge to the working group was to study the feasibility of the proposed VLBI observations, the equipment and time required, and the expected accuracy of the phase center
2000
location
IVS Annual
estimates.
Report
13
Technology
Development
Following
Center
MIT
the nomination
of members
from the three
under the rules of the IVS at the third members of tile WG are: Graham Richard
IVS Directing
Board
the WG was officially
meeting
ILRS-nominated
representative
ILRS-nominated IVS-nominated
representative representative
Tom Herring Ed Himwich
IGS-nominated IVS-nominated
representative representative
Axel Nothnagel
IVS analysis coordinator, IVS chair, ex officio
Brian
Appleby Biancale
services,
Corey
Wolfgang
Schliiter
Tim Springer Nancy Vandenberg
Haystack
on 20 Feburary
Observatory
established 2000.
The
and WG chair
ex ojficio
IGS-nominated representative IVS coordinating center director,
ex officio
The initial meeting of the WG was held on 23 February 2000 in KStzting, Germany, during the first IVS General Meeting. The purpose of the meeting was primarily organizational, but some technical issues regarding the phase center estimates from GPS observations and the proposed VLBI measurements were also discussed.
3.
Initial
working
group
activities
A WG web site was set up in March
2000 at
http://ivscc,
gsfc.
Background information on the phase center email archive are available on the web site.
nasa.
problem,
gov/WG/wgl
general
information
on the WG, and a WG
Following official notification of the IGS and ILRS chairs by the IVS chair that the WG had been established, a general email announcement was distributed to the IGS, ILRS, and IVS communities to inform
them of the existence
for interested response Cannon, 4.
with
expertise
of the WG. The announcement
in relevant
to this invitation, the following IVS members Hayo Hase, Maria Rioja, David Shaffer, and
Summary There
individuals
and purpose
of technical
are two related
A. Measure
discussions
goals
B. Measure the relative each array.
signal
location
phase
to participate
in the WG
an invitation studies.
have joined in the WG discussions: Vincenza Tornatore.
In
Wayne
in 2000
to the proposed
the mean phase center
fields
included
and
VLBI
observations:
of the full, 12-element drive level of the
phased
12 individual
array
on each satellite.
radiating
elements
in
The results of A could be compared directly against the GPS estimates, while the results of B might provide clues to help understand the GPS and VLBI mean phase center results. The key questions to be answered the technical data, and limitations
14
regarding roadblocks
both types
of measurements
are to observing
analyzing the results. on accuracy.
The
the satellites investigations
are what
the potential
with a VLBI to date
have
network,
accuracy correlating
concentrated
2000
is and what the VLBI
on assessing
IVS Annual
the
Report
MIT Haystack Observatory
4.1.
Measuring VLBI
phase
Technology Development Center
the
mean
center
phase
center
measurements
location
will likely employ
an observing
strategy
similar
to narrow-
field VLBI astrometry, in which the VLBI antennas alternately observe a target source (in this case, a GPS satellite) and one or more extragalactic reference sources of accurately known position that lie near the line of sight to the target. The small angular separation between target and reference various types
is intended global
of limits
• With
to minimize
parameters
on how small
an orbital
errors
from propagation
such as station
locations.
the target-reference
period
of 12 hours,
media
The nature separation
a satellite
moves
effects
and from uncertainties
of the GPS orbits
can be made: 1° every
2 minutes.
A reference
that lies right on the path of a satellite will remain within 5° of the satellite minutes, or a few antenna nodding cycles between satellite and reference. • For a 5000-km between
baseline
transverse
to the satellite
the two ends of the baseline
with a satellite
at one station,
in
sets two different
nadir direction,
is 14 °. If a reference
the parallax
source
it will be 14 ° from the satellite
In order to measure the phase center z-component to 20 cm accuracy differential range from satellite to ground between nadir and Earth limb
20
on the satellite
is coincident
at the other
source
for only
in direction
station.
(5a over 1 m), say, the (which is 14 ° away from
nadir) must be measured to an accuracy of (20 cm) × (cos0 ° - cos 14 °) = 6 mm, or 11 ° phase at the GPS L1 frequency of 1575 MHz. All error sources that affect the VLBI phase or delay must be accounted for, to this level of accuracy. These error sources, which are currently under investigation,
include:
• Reference source celestial reference
positions frame must
The L-band positions of the reference sources be known to _0.2 mas to achieve the accuracy
S/X-band astrometry on compact sources this level at L-band may be difficult. • Ionosphere
The
typical
differential
can achieve
L-band
such small uncertainties,
ionospheric
delay
apart is 1-2 orders of magnitude larger than the error budget, between satellite and reference sources must be either measured total
electron
content
models
derived
from global
in the global goal. Global
GPS data
between
but reaching
two directions
5°
so the ionospheric delay or modeled. Ionospheric
appear
to be too inaccurate
[3].
The best approach may be to use the VLBI observations on the satellite and reference sources to estimate the differential ionospheric delay directly from the fringe phase difference between the
GPS
pulsar
frequencies
astrometry
L1 and
L2, in a manner
• Troposphere The tropospheric colocated geodetic GPS receivers. pospheric
delay
similar
to a technique
developed
for L-band
[4].
across
5° should
delay can Systematic be _3
be estimated from GPS measurements errors in the estimates of the differential
with tro-
mm.
• Instrumentation -- When pointing at a GPS satellite, the antenna temperature for a 20m antenna is of order 20,000 K over 20 MHz. Such high levels may cause problems with saturation 4.2.
Mapping The second
distribution
and distortion the
satellite
in the electronics, phased
2000 IVS Annual Report
array,
will ahnost
in the VLBI
baseband
converters.
array
goal of the VLBI observations,
of the phased
particularly
which certainly
is equivalent
to measuring
be more difficult
to achieve
the aperture than
field
the first. 15
Technology
Development
Center
The applicable technique pattern of the test antenna
MIT
is microwave holography, in which the far-field (the GPS transmitter, in this case) is measured
spaced wavelength/(aperture size) radians aperture distribution. For the GPS phased can measure the far-field map will be very poor
pattern only
Haystack
Observatory
amplitude and phase over a grid of points
apart; the Fourier transform of the pattern array, the grid spacing is 13 °, so Earth-bound
gives the observers
at only a few grid points, and the resolution on the aperture field slightly better (i.e., smaller) than the overall size of the array
itself. Super-resolution techniques can sometimes be employed to improve typically require very accurate phase and/or amplitude measurements, noted above may well preclude.
the resolution, but they which the error sources
References [1] Rothacher, M., "Comparison 4(4), 2001 (in press). [2] Springer, T.A., "Common pp. 296-305, 2000. [3] Walker, C., and Chatterjee, Menlo 23, 1999.
of absolute interests
phase center variations,"
GPS Solutions,
of the IGS and the IVS," IVS 2000 General Meeting
S., "Ionospheric
[4] Brisken, W.F., et al., "Measurement 541, pp. 959-962, 2000.
16
and relative antenna
corrections
of the parallax
using GPS based models,"
Proceedings,
VLBA Scientific
of PSR B0950+08 using the VLBA," Astrophys.
2000
IVS Annual
J.,
Report
IAU resolution
IVS
IVS
was
tive
July
XXIVth
recognized 1999
when
General
ester/England, IAU resolution: IAU
as
Resolutions
The International
is a Service
a Service
the
of the
General
Assembly August
2000
BI.1
Maintenance
Astronomical
International
Assembly
of the the
of the
was
IVS
and
is also
Association held
International
recognized
Establishment
of reference
Recognising 1. the importance of continuing operational (VLBI) to maintain the ICRF,
3. the progressive 4. the need
observations transformation
shift between
to maintain
(IAG)
Union
as a Service
Since
IAU
held
of the
Frames
effec-
in
IAU.
and
the
Manch-
Here
is the
Systems
Union
definition
2. the importance of VLBI specify the time- variable Frames,
of Geodesy
Birmingham/England.
of Reference
(1997) specifies that "the fundamental reference Frame (ICRF) constructed by the IAU Working
2. that Resolution B2 of the XXIIIrd General Assembly shall be the primary realisation of the International wavelengths", and need for accurate
in
Astronomical
Noting 1. that Resolution B2 of the XXIIIrd General Assembly frame shall be the International Celestial Reference Group on Reference Frames",
3. the
IAU
the
the optical
systems
(1997) specifies "That the Hipparcos Celestial Reference System (ICRS)
brought
observations
about
made
with
by unprecedented
Very
Long
Baseline
precision,
frame
realisation
and
the ICRF,
as close as is possible
and
Interferometry
to the operational determination of the parameters between the International Celestial and Terrestrial
Hipparcos
Catalogue at optical
needed to Reference
and to the ICRF
Recommends 1. that IAU Division I maintain the Working I members to consult with the International of the ICRS, 2. that the IAU recognise Service Organization,
the International
3. that an official representative Celestial Reference Systems, 4. that
the
IAU continue
of the
to provide
Group on Celestial Reference Systems formed from Division Earth Rotation Service (IERS) regarding the maintenance
VLBI
IVS
an official
Service
be invited
(IVS)
for Geodesy
to participate
representative
and
in the
Astrometry
IAU
to the IVS Directing
Working
as an IAU
Group
on
Board,
5. that the astrometric and geodetic VLBI observing programs consider the requirements for maintenance of the ICRF and linking to the Hipparcos optical frame in the selection of sources to be observed (with emphasis on the Southern Hemisphere), design of observing networks, and the distribution of data, and 6. that the scientific community continue with high priority ground- and spacebased the maintenance of the optical Hipparcos frames and frames at other wavelengths the frames to the ICRF.
2000 IVS Annual Report
observations (a) for and (b) for links of
17
._.
r:
--
/'
,,j
MIT
VLBI
Standard
Interface Alan
International agreement has now been accomplished.
Haystack
Observatory
Specification
Whitney
and finalization of a VLBI Standard The final specification was released
Interface in August
(VSI-H) specification 2000 after 18 months
of hard work by the dozen members of the VSI Technology Coordination Group. This specification promises to help ease the long-standing incompatibility between VLBI
data
systems systems
systems.
The VSI-H
to be interchangeably in a '_plug-compatile"
specification connected fashion,
is designed
to allow heterogeneous
network
The fledgling
data-transmission,
VSI concept
of the GEMSTONE
meeting
or whatever
leading
to the
in Tokyo
digital-data
to both data acquisition and data processing (correlator) something that is not currently possible. Furthermore,
looking to the future, the VSI-H specification is designed tional recording/playback systems, such ms magnetic tape, optical fibers, available.
VLBI
various
current
in January
to be compatible not only with but also with magnetic or optical
future
data
transmission
specification 1999 and
technology
was first proposed
was discussed
tradidiscs, may be
at the
by a small
time
interested
group at that meeting. With the support of IVS, as well as the a.ntronomy-VLBI community, a VSI Technology Coordination Group was appointed, composed of experts representing all of the major world institutions involved in the development of VLBI equipment. The members of the VSI-TCG are Wayne Cannon (York Ferris (ATNF, Australia),
University/Crestech, Canada), Brent Carlson (DRAO, Canada), Dave Graham (MPI, Germany), Tetsuro Kondo (CRL, Japan),
Dick Nori
Kawaguchi (NAO, Japan), Misha Popov (ASC, Russia), Sergei Pogrebenko (JIVE, Netherlands), Jon Romney (NRAO, U.S.), I_lph Spencer (Jodrell, England), Alan Whitney (Haystack, U.S., Chairman)
and
Rick Wietfeldt
(JPL,
U.S.).
e-mail discussions, plus three (multi-hour!) international VSI meeting held at Haystack The current VSI-H specification and will be extended and ameuded groups are known to be developing dard. The full VSI-H specification http://dopey.haystack.edu/vsi/index.html.
The
VSI-
H specification
international telephone Observatory in February
by intensive and
a two-day
is intended as a starting point from which to progress, as needed. It is heartening that already at least three or adapting VLBI data systems to meet the VSI-H stanis reprinted in this article, and is available on-line at
The next job of the VSI TCG is the definition of a companion called VSI-S, which we hope to have in place by the end of 2001.
18
was shaped conferences 2000.
VSI software
2000
standard,
IVS
Annual
to be
Report
VLBI
Standard
Hardware
Interface Revision 7 August
Table
Prologue Introduction Intent of the VSI-H Specification Structure of the VSI-H Specification Levels of Compliance Assumptions on which VSI-H Specification Data Transmission System (DTS) Structure
7.
Data Input Module (DIM) 7.1 DIM Interface 7.2 The Data-Observe-Time
9.
- VSI-H
1.0 2000
of Contents
O. 1. 2. 3. 4. 5. 6.
8.
Specification
(DOT)
is Based
Clock
7.3 Example of DIM Operation Data Output Module (DOM) 8.1 DOM Interface 8.2 The Requested Observe Time (ROT) Clock 8.3 Speed-up/Slow-down Data Reproduction 8,4 Delay Offset 8.5 Example of DOM Operation Signal Selection and Switching 9.1 DIM 9.2 DOM
10. Signal Descriptions 10,1 DIM Input Signals 10,2 DIM Output Signals 10.3 DOM Input Signals 10.4 DOM Output Signals 11. Signal Timing Relationships 11.1 General 11.2 Timing Ticks 12. Interconnect Hardware Specifications 12.1 LVDS Interfaces 12.2 TTL Interfaces 12.3 Control Interfaces 13, Test Vectors 13.1 General Characteristics 13.2 Test Vector Generator 13.3 Test Vector Timing Relationships 13.4 Test Vector Receiver 14. Other Notes and Comments 14.1 14.2 14.3 14.4 14.5 14.6
Data-Replacement Formats Media Translation (Tape Copying) Usage of PDATA/QDATA Usage of PVALID/QVALID Multiple Parallel DTS's Multi-Port DTS
14.7 Validity per Bit Stream 14.8 Higher Clock Rates 15. Glossary 15.1 General 15.2 Signals 16. References Appendix A: Revision
History
19
Tables Table Table Table Table Table Table Table Table Table Table Table Table Table
l: 2: 3: 4: 5: 6: 7: 8: 9: 10: I I: 12: 13:
DIM Input Signals Required combinations of clock frequencies and internal bit-stream DIM Output Signals DOM Input Signals Required frequency combinations of DPSCLOCK and RCLOCK DOM Output Signals Timing-Tick Min/Max Durations MDR-80 Pin Allocations (Data Interface) MDR-14 Pin Allocations (Timing Interface)
data rates
Suggested Re,,erse-Channel Signal Assignments LVDS Timing Specification and Values (ns) at Rated Frequencies DB-9 Pin Allocations (EIA/TIA-574) TVG data outputs
for first 20 data bits following
1PPS/RIPPS
Figures Figure Figure Figure Figure Figure Figure Figure
1: 2: 3: 4: 5: 6: 7:
VSI-H Functional Block Diagram LVDS Timing Relationships LVDS Transmitter Output Eye Pattern LVDS Receiver Input Eye Pattern LVDS Waveform Transition Definitions Test-Vector Generator Schematic TVG Timing
Relationships
20
O. Prologue The incompatibility of various VLBI data systems has long been recognized serious obstacle to the realization of the full potential of VLBI observations.
as posing Sporadic
efforts have developed over the years to define allow observations recorded on different VLBI
which would at a common
correlator,
but these efforts
The establishment
have foundered
of the Global
VLBI
VLBI
community,
standardization these
roots
could
proceed
that the present
The fledgling
group to create
experts
representing
VLBI
in the early
1990's,
community but serving the broader interests Service (IVS) in 1998, serving primarily the an organizational
leading
framework
for which
and sanctioned
to the current
meeting
in Tokyo Support
a VSI Technology The members
specification
in January
fashion.
of
efforts
at
It was from
world
Group
institutions
of this committee
was first proposed
1999 and was discussed
was then sought
Coordination
all of the major
equipment.
(GVWG)
was initiated.
at that meeting.
GVWG
reasons.
Group
in a more organized
effort
VSI concept
time of the GEMSTONE interested
provided
for various
Working
growing primarily from the space-VLBI astronomy, and the International VLBI geodetic
a common interface standard data systems to be processed
a
and received (VSI-TCG)
involved
are Wayne
from
at the by a small
1VS and
comprised
of
in the development Cannon
of
(York
University/Crestech, Canada), Brent Carlson (DRAO, Canada), Dick Ferris (ATNF, Australia), Dave Graham (MPI, Germany), Tetsuro Kondo (CRL, Japan), Nori Kawaguchi
(NAO,
Netherlands), Whitney Early
Japan),
Misha
Jon Romney
(Haystack,
(NRAO,
Russia),
Ralph
Sergei
Spencer
and Rick Wietfeldt
it was decided
first on hardware,
(ASC,
U.S.),
U.S., Chairman)
in the discussions
concentrating
Popov
hence
Pogrebenko
(Jodrell, (JPL,
England),
international
VSI meeting
to separate
the hardware
and software
this VSI-H
specification,
to be followed
held at Haystack
Alan
U.S.).
companion software specification, VSI-S. The VSI-H specification intensive e-mail discussions, plus three (multi-hour!) international and a two-day
(JIVE,
VSI, by a
was shaped by telephone conferences
Observatory
in February
2000.
The current VSI-H specification is intended as a starting point from which to progress, and will be extended and amended as requirements and technology demand. It is heartening adapting
that already VLBI
The VSI-H
specification
even well beyond particularly Wietfeldt,
at this writing
data systems
those
acknowledge the entire
at least three groups
to meet the VSI-H
represents named
the work of many
in the formal
the important
Japanese
group,
are known
to be developing
or
standard. individuals
VSI-TCG.
contributions and the Crestech
at many
The chairman of Dick Ferris, group
Alan
institutions,
would
like to
Jon Romney,
Rick
in this effort.
Whitney
MIT Haystack
Observatory
25 July 2000
21
1. Introduction This document 'Data
defines
Transmission
a VLBI
System'
both data-acquisition of effort.
system
The interface
systems,
network
hide the detailed from
The VSI-H
specification
basic
connector,
A VLBI
defines specifies
to be interfaced
(DPS)
to
with a minimum
recording/playback
systems.
of a 'channel
on a single
It is designed
to
the data to be
quantum',
standard
quantum'
and 4.096
Gbps.
Standard
to and from a VLBI
manner.
a 'channel
to 2.048
Software
system
with traditional
of the DTS and allow
the notion
use of two or more
Standard
DTS's
and even direct-connect
characteristics
with extensions
by parallel
(VSI-H)
and data-processing
DAS to DPS in a transparent
specification
Interface
heterogeneous
to be compatible
data rate that can be carried
VSI-H
simply
(DAS)
data transmission
transferred
Standard
that allows
is defined
completely
maximum
Hardware
(DTS)
VSI-H
quanta'.
Interface
(VSI-S)
is the
data connector.
of 1.024 Gbps Higher
'channel
which
The
on a single
80-pin
data rates may be realized
to accompany
VSI-H
is proposed
but does not yet exist. 2. Intent
of the VSI-H
Specification
The intent of the VSI-H specification is to define a standard electrical and timing interface, along with a control philosophy. In this sense, VSI-H is not intended to be completely case;
'plug
the future
customization hardware
as well.
The VSI-H
VLBI
specification
of tape media
extensions.
Adherence
to the optional
4. Levels
of Compliance with the VSI-H
at normal
A - Fully compliant
Level
B - Compliant
data-taking
at the that now
and data-correlation of other
and parallel
as a base specification extensions
related
operation
activities
of multiple
specification
standard,
is expected
but not mandatory.
for all future
systems
Existing systems are expected For the purpose of indicating
two levels
of compliance
with the base VSI-H
with the VSI-H
plus a set of optional
is desirable
by parties agreeing to the VSI-H specification. modified to comply on a best-effort basis only.
Level
interface
Specification
is structured
to the VSI-H
in each
the software
incompatibilities
note will also be made
(i.e. tape copying)
specification
of compliance
customization
minimize
of a standardized
of the existing
aimed
However,
The VSI-H
Full compliance
many
software
will hopefully
the adoption
is primarily
of the VSI-H
at least some
specification
data systems.
to VLBI.
such as translation DTS's. 3. Structure
VSI-S
help to relieve
various
commonplace
and will require
ofa
Nevertheless,
level should
exist between
tasks
and play', adoption
designed to be the degree
are established:
specification
base specification
except
for one or more
of the
following: 1.
Support
for fewer
than 32 bit streams
2.
Incomplete
signal-switching
3.
Incomplete
support
4.
Incomplete
delay-offset
(Section
7)
or active-signal-selection
of full range support
of fCLOCK(Section (Section
capability
(Section
9)
10)
8.4)
22
5. Lack of supportfor PDATA/QDATA and/orPVALID/QVALID signals (Sections10and 11) 6. Incompletetest-vectorcapability(Section13) 7. Data-replacement format(Section14) Non-supportof the optionalextensionsto 64 and 128MHz doesnot affectVSI-H compliance. 5. Assumptions The VSI-H •
on which
specification
VSI-H is based
The DTS is fundamentally Data-Acquisition
•
System
The meaning stream
•
a receiver
and transmitter
bit streams agreed
and transmitted
upon
bit-stream
every
time-tag
Note that, under or format optical
applies
bit-stream
must
these
assumptions,
of the medium
fiber, Internet
as indicated 1.
streams,
of the VSI-H
accompanied time-tag
The 'Data
The DAS
(e.g. the
however
time-tag
(DIM)
7. Data
Input
A simplified Figure
the DTS;
medium
on the type
magnetic
tape, disk,
is allowed.
the DTS is divided
into two logical
1.
modules,
is responsible clock
time'),
for accepting
and common
and sending
them
multiple
1-second
parallel
bit
tick, applying
to a transmission
a
medium
(tape,
Module'
(DOM)
accepts
data from the transmission
DIM and DOM Module
model
may reside
either
in a single
physical
medium, the data-streams
module
or in
modules.
(DIM)
of one 'channel
quantum'
of the Data
Input Module
is shown
in
1.
7.1 DIM 7.1.1
bit in
Structure
by a common
DTS (DIM plus DOM)
physical
of every
rates
etc.).
Output
separate
clock
are placed
decodes the accompanying 'observe-time' information, and recreates in accordance with an external clock and 'l-second' tick. The entire
all received
of the DTS.
or specifications
the data through
specification,
('observe
disc, fiber-optic, 2.
no restrictions
(DTS)
but the actual
and all bit-stream
at the output
is a
1:
Input Module'
common
bit streams.
used to transport
System
in Figure
The 'Data
or slowed-down),
or any other type of transmission
6. Data Transmission For the purposes
to all parallel
a
and DPS.
rates may be different
are the same,
be fully recoverable
between
a bit-stream
samples,
the DAS
rate into the DPS may be speeded-up
A single
normally,
with particular
clock
bit streams
System.
between
bit-stream information rates on acquisition on transmit are the same. •
of parallel
is not specified;
bits associated
is to be mutually
playback
set of assumptions:
and a Data Processing
of individual
The received
is Based
on the following
of sign or magnitude
meaning
Specification
Intepface
Input
signals
BS0 through same
from the DAS
to the DIM-
BS31 - 32 parallel
rate, which
bit-streams,
may be selected
all sampled
by the DIM at the
to be 2, 4, 8, 16 or 32 MHz, 23
corresponding aggregate Any
rate'
1, 2, 4, 8, 16 or all 32 input channels Only
DOM
'active'
bit-streams
(fBs0. The maximum
for one 'channel
may be selected
are sampled
quantum'.
and marked
and made
available
as
at the
output.
Optional
extension
aggregate
3.
information
DIM input data rate is 1.024 Gbps
'active'.
2.
to the 'bit-stream
rates
CLOCK
of fCLOCKto 64 and 128 MHz provides
of 2.048 and 4.096
- a clock accompanying
reference
frequency
extension
to 64 or 128MHz.
respectively.
the bit-streams,
for the DIM,
1PPS - a lpps tick which which timed
Gbps,
maximum
also providing
a
at 2, 4, 8, 16 or 32 MHz with optional
Note
fCLOCK_>fBSl.
defines
the corresponding
parallel
data
bits
are to be time-tagged on the integer second. The 1PPS signal is to coincide with the data bit taken on the second _tick (the 'TOST'
bit). 4.
PVALID content
- signal
that specifies
the 'validity'
and use of the PVALID
signal
of the BSn bit streams.
is not defined
The
by the VSI-H
specification. 5.
A standard
8-bit ASCII
asynchronous
may send a burst of up to 2048 tick. The content specification. 7.1.i
DIM Control
and use of this information
interface
is a 2-way
in both RS-232
specific
critical
messages
1PPS pulses,
transmitted
7.1.3
Other
1.
ALT1PPS
- a monitor
2.
in Figure
The DOT clock
specific
(possibly for 1PPS,
signal
adjacent
1PPS pulses.
unit, they may share
asynchronous) as indicated
signal in Figure
second
(DOT)
atomic
from the DIM which
a
which
of
clock.
allows
tick (see Section
may be
1. An example
confirmation
of
7.2).
Clock
1, the DIM maintains
an internal
Data-Observe-Time
(DOT)
clock
properties:
is the master
each incoming
The DOT clock given
to a
can be reliably
in the same physical
of the DOT-clock
has the following
mark
connected
sent to the DIM between
messages
might be the lpps tick from a station
7.2 The Data-Observe-Time
1.
by the VSI-H
interface,
and normally
can be reliably
reside
as a substitute
DOTMON the epoch
which
1PPS
interfaces.
ALT 1PPS - an external
As shown
which
Signals
selected
2.
each
both controls and monitors the operation must be aware of 1PPS ticks to the extent
from the DIM between
set of control
communications
and that certain
If the DIM and DOM single
PDATA,
between
is not specified
and Ethernet,
computer. The control interface of the DIM. The DIM controller that certain
of information
Interface
The DIM control implemented
serial data stream,
bytes
clock
within
the DIM,
data bit with its current
may be set to a specified
reading
second
and is used to unambiguously to the full resolution
of time (presumably
of CLOCK.
UTC)
on a
1PPS or ALT 1PPS tick. 24
3. Onceset,theDOT clock keepstime solelyby countingCLOCK cycles(i.e. subsequent1PPS/ALT1PPSticks areignoredby the DOT clockunlessthe DOT clock is expresslycommandedto bereset). 7.3 Example
of DIM
The following observing 1.
is an example
specified
Through
second
1PPS/ALT DOT
bit streams
the Control
set, the DOT
of operations
of a DIM in a normal
Through selected
by the DIM and relayed
the DOT
of time on the next clock keeps
1PPS signals.
epoch
will be sampled
Interface,
clock
is commanded
to be set to a specified
1PPS (or ALT 1PPS) tick [see Note
time by counting
cycles
The DOTMON
of CLOCK,
monitor
signal
the Control Interface, the DIM is commanded input bit streams to the transmission medium. with its accompanying
At the end of the observing Interface)
to the DOM.
6 below].
ignoring
allows
Once
subsequent
confirmation
of the
setting.
must be transmitted 4.
sequence
situation:
integer
3.
of a typical
Through the Control Interface, the DIM is configured to accept any particular subset of 1, 2, 4, 8, 16 or 32 of the incoming bit-streams, all at a specified bit-rate. Only these
2.
Operation
to cease
period,
transmitting
to begin transmitting the Each bit in each data stream
time tag, either
explicitly
the DIM is commanded
or implicitly.
(through
the Control
data.
Notes: 1.
The method
the DIM uses to record/transmit
the VSI-H 2.
3.
the VSI-H
Some DIM information, 'antenna
of the DIM
on-source'), and/or
prohibits
signals
The Control
specified relationship DOTMON
scheme
any multiplexing
which
are
or de-multiplexing
data into bit streams
that the DTS designer so long as the DOM
presented
to the
is free to implement
output
bit-streams
any
are faithful
input bit-streams.
to the bit-streams
to the DIM via the Control data streams.
of ALT1PPS, are contained
Interface
be notified
the control
internally
sampled
however,
in addition
PVALID
With the exception
request,
requirements
themselves.
Interface
The VSI-H
Such
or, in some
specification
(i.e.
information cases,
neither
via the
requires
nor
any such capability.
interface 6.
and configuration
systems may have the ability to transmit additional low-data-rate such as bit-stream identification and high-level global validity
may be transmitted PDATA
noted,
multiplexing
reproductions
5.
to transform
It is explicitly
DTS-internal
control
of the DAS to implement
that may be necessary
4.
to
specification.
It is the responsibility DIM.
data is irrelevant
specification.
Each type of DIM may have various outside
data or to time-tag
must be designed in a timely
computer integer
command
In addition,
or externally the control
Interface, (see Section computer
all DIM 12). can, on
of a 1PPS/ALT1PPS
tick so that
the DIM to set the DOT
1PPS/ALT
1PPS and DOTMON
the DIM [preferred]
relationship.
connector
so that the controlling
of time on the next
1PPS/ALT
and the Control
80-pin
way of the occurrence
can unambiguously
second
between within
DOTMON in a single
1PPS tick.
to verify
the 1PPS/ALT1PPS should
to a
The subsequent
can then be monitored
computer
clock either vs
be able to verify
the 25
DOT epochby requestingthatthe DIM reportthe DOT settingat theoccurrenceof thenext DOTMON tick. 8. Data Output A simplified 8.1 DOM $.1.1
Module
model
(DOM)
of the Data Output
Module
is shown
in Figure
1.
Interface
Input
timing
signals
from the DPS -
1.
A clock, DOM.
DPSCLOCK,
2.
A 'l-pps
tick',
from the DPS which
DPS1PPS,
which
acts as a reference
is used to set an internal
frequency
DOM
'Requested Observe Time' (ROT) clock to an integer-second similar to the way 1PPS sets the DOT clock in the DIM. 8.1.2 1.
Output
signals
from the DOM
Reconstructed of the active
bit-streams, sampled
RBS0 through
bit-streams
RBS31 - accurate
transferred speeded
fBsl at the input to the DIM, and (ii) switching
2.
RCLOCK
- clock
3.
R1PPS
rate'
or slow-down
respected
to ROT1PPS.
corresponding
the reconstructed
The R1PPS
ROT1PPS - lpps tick from ROT as the reconstructed bit streams.
5.
QVALID the DOM
to be correct
extended
to include
as a pass-through 6.
signal
tick always
clock,
subject
indicating
sophisticated
of PVALID
an
subject
by a specified
marks
to the same amount
with
the data bit(s)
input. to the same speed-up
that the reconstructed
(i.e. tape is reproducing
more
allows
properly).
validity
or slow-down
data are judged
May optionally
indications,
by
be
such as pulsar
gating,
or
from the input to the DIM.
QDATA - A standard 8-bit ASCII serial data stream which may send a burst of up to 2048 bytes of information framed between each R1PPS or ROTI PPS tick (user can select
to frame
of this information 7.
the bit streams,
bit' at the DIM
4.
- a l-bit global
the DOM
to
bit streams.
as RBSn, but may be delayed
to the 'TOST
with respect
signals RBS0..RBS31. The rate called the 'reconstructed
1PPS accompanying
speed-up
within
down
in so far
(fRBSl).
accompanying
- reconstructed
the
reproductions
from the DIM except
up or slowed
arbitrary mapping of bit-streams to output reconstructed bit streams are at a common information
called
in a manner
to the DPS -
as (i) they may be collectively
bit-stream
clock
epoch
for the
Control
Interface
QDATA
--The
interface,
encompassing
monitors
the operation
DOM
either;
both RS-232
adjacent
that certain DPS1PPS
see Section
by the VSI-H
control
of the DOM.
DPS 1PPS to the extent between specific interface.
between
is not specified
interface
14.2).
is a 2-way
and Ethernet, The DOM
The content
and use
specification. communications
which
controller
messages
can be reliably
pulses.
May be shared
both controls must
be aware
sent to/from
and of the DOM
with DIM control
26
8.1.3Other
Signals
ROTMON
- a monitor
the epoch
signal
of the ROT-clock
8.2 The Requested
Observe
from the DOM second
which
allows
tick (see Section
Time (ROT)
confirmation
of
8.2).
Clock
The DOM maintains an internal Requested-Observe-Time (ROT) clock which maintains the reference time to which the re-constructed data are to be synchronized. The ROT clock has the following 1.
The ROT clock
2.
Once
properties: is set to a specified
set, the ROT
clock keeps
subsequent
DPS1PPS
be reset).
The monitor
second
time solely
ticks are ignored signal
of time on a given by counting
unless
ROTMON
DPSCLOCK
the ROT
allows
DPS1PPS
cycles
is expressly
confirmation
tick. (i.e.
commanded
of the ROT
to
epoch
setting. 8.3 Speed-up/Slow-down Some
systems
slowed-down
Data
may also allow by compared
Reproduction the DOM
to the DIM
output
bit rate (fRBS0 to be speeded-up
input rate (fBs0.
In such cases,
or
the ROT-clock-
increment per DPSCLOCK-cycle must be commanded to change correspondingly. rates of RCLOCK, ROT 1PPS, R1PPS and RBS, will all change correspondingly. The VSI-H
specification
does it constrain 8.4 Delay
does not mandate
the implementation
any speed-up
or slow-down
The
capability,
nor
of such capability.
Offset
In a storage-based
DPS system,
where
the data are actually
captured
to a transportable
storage medium and then replayed at a later time, a delay-offset capability in the DOM allows control of data alignment into the DPS. In these storage-based systems, VSI-H specifies
that the DOM
streams
with respect
a bit offset. the delay signals delay
This allows offset
the capability clock,
adjustment
with respect
is zero,
ROT1PPS
data with the proper
delay
to offset
as indicated
of the data delay
is set to a non-zero
are delayed offset
include
to the ROT
value,
the delay
in Figure
of the reconstructed
into the DPS for processing.
the RBSn bit streams,
is being
output
are coincident.
QVALID
specified.
When
indicates
as
When
RI PPS and QVALID
to the ROT 1PPS tick by the amount and R1PPS
bit-
1. The delay is specified I
the
that valid
from the DOM.
The range of the available delay offset in a storage-based DPS system shall be sufficient to cover at least + 0.5*ROT 1PPS. This allows an arbitrarily large offset (with respect to some DPS master offset, z The design independently
clock)
of the DOM without
In a direct-transmission DOM
and not stored
to be specified
should disturbing
with a combination
be such that the ROT
of ROT
setting
clock and the delay
and bit
offset
can be set
the other.
DPS system, in a transportable
where
the data are transmitted
medium,
the required
delay
directly offsets
from DIM to are primarily
a
That is to say that QVALID remains synchronized to the RBSn bit streams to which it pertains. 2 It has been pointed out that implementing a specified delay in the DIM between IPPS and the DOTgenerated lpps may also provide some useful features, such as test-vector verification in some cases, or in compensating for a known epoch error in I PPS or ALT1PPS. The implementation of such a delay capability in the DIM is optional and not part of the VSI-H specification. 27
function DPS
of the geographic
is assumed
no delay
extent
to implement
of DOM
is an example
data-playback
situation:
Through subset
the Control
Through
integer
In this case, the and VSI-H
8.4).
ignoring
mandates
the Control
selected
input bit streams
the ROT Once
Interface,
to reproduce
is commanded
set, the ROT
of mechanical
the recorded
data to the ROT offset,
in a common
any desired
to be set to a specified
clock
offset
may also be
keeps time by counting
cycles
of
DPS 1PPS signals.
the DOM
For tape-playback
a delay
clock
synchronized
combination (with
is configured
of a DOM
sent to it by the DIM.
subsequent
Through
the ROTclock.
of operations
of time on the next DPS 1PPS tick; a delay
(see Section
DPSCLOCK,
4.
interface,
second
sequence
the DOM
bit streams
the Control
specified
of a typical
Interface,
of the 'active'
UTC
3.
network.
requirements
Operation
The following
2.
data-collection data-delay
capability.
8.5 Example
1.
of the VLBI
the necessary
is commanded
systems,
this means
tape positioning clock.
to begin
to the ROT clock
the DOM
and electronic
When
the output
if any) and valid, the QVALID
At the end of the data-period of interest, the DOM Control Interface) to cease transmitting data.
transmitting
or specified
must use a
buffering
to synchronize
data are properly
signal
the
bit offset from
synchronized
is asserted
is commanded
logical
(through
'true'. the
Notes: 1.
Note that the reconstructed data-stream Section
2.
streams
conjunction simple
5.
the ability
interface
to reproduce
additional
operation,
operations.
The VSI-H
DPSCLOCK,
are contained
and monitoring
to transform
specification
the
information
etc. in addition
QDATA
to transfer
internal
with DPS1PPS
of DPS 1PPS,
The procedure for setting DOT clock in the DIM.
PDATA,
to have some
aligned
signals
for example,
counterpart,
data (see
low-data-rate
identification,
serial-data
transmitted
for the
or demultiplexing).
in the DOM
the DPS is presumed
the exception
as multiplexing
via the QDATA
Since
With
necessary
may be accessed
of QDATA.
not be precisely
replaced
Such information
with its DIM
need
data (such
such as bit-stream
a tape-copying
tape copying
or intentionally
possibly
by the DIM.
cases,
usage
all DOM 12.1). 6.
may have
into usable
from the DIM, or, in some
performing
are, except
of the DPS to do any manipulations
themselves.
Interface
errors
to the data sampled
bit streams
DOM's
transmitted
4.
identical
It is the responsibility
Some
from the DOM
clock rate and for playback
14.1),
reconstructed 3.
data streams
to the bit-
via the Control stream.
When
may be used in time-tag
data to execute
does not mandate
buffering,
ROT1PPS
content
or
and RCLOCK
and DPSCLOCK. ROTMON
in a single
80-pin
of the ROT
clock
and the Control connector
is similar
Interface,
(see Section
to that for the
28
9. Signal
Selection
and Switching
9.1 DIM As implied 'active'
in the discussions
any subset
selected
the DIM
must include
of 1, 2, 4, 8 or 16 of the 32 potential
set of bit-streams
DTS to more rates. 3
above,
efficiently
is required
BS, input
to be transmitted
use the transmission
the capability
data streams.
to the DOM.
medium
in cases
to select
as
Only
This enables
of reduced
the
the
aggregate
data
9.2 DOM The DOM
is required
to reconstruct
by the DIM.
However,
reconstructed
bit-streams
crossbar
switch
implement module
10. Signal
must include
to any DOM
as a functional
this specification
(presumably
only the 'active'
the DOM
RBSn output
illustration
bit-stream.
manner,
its own control
a separate
a 32x32
is free to external
interface).
Signals
Frequency/Period
Voltage
Comments
CLOCK
fCLOCK= 2, 4, 8, 16, 32 MHz
LVDS(see Section
to allow
with optional extensions to 64 and 128 MHz (see Table 2); dynamic variability IPPS
fCLOCK
1 per fCLOCKcycles
12.1)
LVDS
of CLOCK
Rising edge should
cycles
ALT 1PPS
Alternate
BSo n=0 to 31
Sampled by DIM at 'bit-stream information rate' (fBs0;
1PPS signal
with rising
LVDS
May be asynchronous
LVDS
For all clock rates, TOST bit (see Section 11.1) must be coincident with 1PPS; one data bit accepted
115 kbaud 8-bit serial data;
LVDS
every
with CLOCK
2k CLOCK
cycles thereafter
Up to 2048 bytes to be received
one stop bit, no parity
between
each
I PPS tick Table
1: DIM
Input
fCLOCK
If.CLOCKI
(Mnz) 4
Signals fnsl IfRBSd (Mbps) 16
32
64
128
Z Z
z z
z
bit-stream
data
2 4 8
Y Y Y
Y Y
Y
16 32
Y Y
Y Y
Y Y
Y Y
Y
(opt) 128 (opt)
Z Z
Z Z
Z Z
Z Z
Table
combinations
2: Required
be synchronous
edge of data bit to be tagged as 'taken on the second tick' (the 'TOST' bit); see Figure 2
fBSl _ fCLOCK PDATA
sets maximum BS. sample rate; variability for high-velocity spacecraft applications
up to +100 ppm
(e.g. 1 per 32x106 CLOCK for 32 MHz CLOCK
of clock
frequencies
and
internal
rates
2 notes: 1.
'opt'
2.
'Y' one)
indicates indicates
output
capability
bit-stream
See also
optional required.
'Z'
indicates
required
if that
optional
clock
frequency
(or a higher
is implemented.
3 A signal-switching
required.
1 shows
but the designer
including
Signal
DOM
Figure
to it
any of the
Descriptions
10.1 DIM Input
Table
transmitted
to connect
of this capability,
in any satisfactory
containing
set of bit-streams
the capability
at the DIM
ordering
footnote
is more
in Section
input directly
may be useful compatible
to order with
the bit-streams
a target
DPS,
so that the default
but this capability
is not
13.4
29
3.
Clock frequencies
of 64 and 128 MHz are optional
Notes: 1. Use
of ALT 1PPS is intended for systems where independent external source such as a hydrogen
cannot
be guaranteed
CLOCK
cycle
to be synchronous
ambiguity
in the setting
Strictly
speaking,
the ALT 1PPS signal
to the VSI-H standard.
the station 1PPS is provided by an maser. In such a case, the ALT 1PPS
with CLOCK,
which
of the DOT clock.
little consequence so long as the DOT clock cause a timing discontinuity. 2.
extensions
may result
in a +1
This will normally
is not subsequently
need only be a single
reset,
pulse
which
be of could
to set the DOT
clock, but is typically a repetitive signal at a 1-pps rate. Following the setting of the DOT clock, the DOTMON monitor signal generated by the DOT clock is a useful indicator 3.
Each
of proper
DOT-clock
input bit-stream,
periods
of CLOCK,
sample
rate is known
BSn,
where
by the DIM only once every
as the 'bit-stream to always
by the relevant
information
rate'
2 k, k=0,1,2 ....
cell value (fBsI).
in Table
This allows,
run at fCLOCK, even though
fBSl is lower
2. This for than the
The inclusion of PDATA is primarily for future use, particularly for tape copying, where the output of a DOM can be connected directly to the input of a DIM. In such a case, the QDATA
output
DIM to automatically (see Section 14.2). 5.
is sampled
k is determined
example, the DAS samplers DAS sample rate. 4.
synchronization.
Any discontinuity variability be reset.
10.2 DIM
update
the DOT
or frequency
of+100
Output
from the DOM
change
ppm, will normally
can dynamically
clock.
Other
of CLOCK, require
transmit
data time to the
uses of PDATA
are also possible
other than the allowed
the DIM,
including
dynamic
the DOT clock,
to
Signals
Signal
Frequency/Period
Voltage
Comments
DOTMON
Same as 1PPS
TTL
For monitor
purposes
only
Table 3: DIM Output Signals
Notes: 1.
The DOTMON signal provides a useful synchronized to 1PPS/ALT 1PPS.
2.
The inclusion
10.3 DOM
Input
in the DIM
of other
useful
monitor
that indicates
monitor
signals
is encouraged.
Signals
Signal
Frequency/Period
DPSCLOCK
Allowed
frequency
is dependent
on
Voltage
Comments
LVDS
Sets max fRas_;
fRCLOCK,as given in Table 5; dynamic variability up to +100 ppm DPS 1PPS
the DOT is properly
1 per fDPSCLOCK cycles of DPSCLOCK (e.g. 1 per 32x106 DPSCLOCK
variability spacecraft LVDS
to allow for high-velocity applications
Sets epoch of ROT clock second tick
cycles for fDPSCLOCK=32MHz Table 4: DOM Input Signals
Notes:
30
1.
The DPS 1PPS signal presumably
2.
at the beginning
Any discontinuity variability be reset.
is used only once to set the ROT clock
upon
command,
of a scan or tape.
or frequency
of_100
epoch
change
ppm, will normally
in of DPSCLOCK, require
other than the allowed
the DOM,
including
the ROT
clock,
to
fRCLOCK
fDPSCLOCK
(MHz) 16
(MHz) Y Y 16 32
Y Y Y
64 (opt) 128 (opt)
Z Z
Y Y Y Y Z Z
Table 5: Required
frequency
32
Y Y
Y
Y
Y
Y
Z Z
Z Z
Z Z
combinations
of DPSCLOCK
64
128
Z Z
Z
and RCLOCK
Table 5 notes: 1. 2.
'opt' indicates optional. 'Y' indicates required. 'Z' indicates required if that optional clock frequency (or a higher one) is implemented. CLOCK frequencies of 64 and 128 MHz are extensions to the VSI-H standard.
.
10.4 DOM
Output
Signals
Signal
Frequency/Period
Voltage
Comments
RCLOCK
fRCLOCK is dependent on fDPSCLOCK, according to Table 5
LVDS
Sets max output reconstructed bitstream information rate (fRRsl)
R 1PPS
1 pulse per second of ROT clock time
LVDS
Ratio of RI PPS to DPS 1PPS pulse frequencies depends on DOM speed-up factor (see Notes)
ROT1PPS
Same as RIPPS
LVDS
Coincident with R1PPS if delay=0 or delay option not implemented
RBSn n=0 to 31
fRBSI=fR¢,LOC_K/2
LVDS
May be arbitrarily
QVALID
Global logical indication that data is sync'ed and valid; no period
LVDS
QDATA
l 15 kbaud 8-bit serial data; one stop bit, no parity
LVDS
accordance
k, k:0,1,2 .... in with Table 2
re-mapped
Up to 2048 bytes transmitted bem:een successive R IPPS or ROT 1PPS ticks (selectable)
TTL
Same as ROTI PPS
ROTMON
Table 6: DOM Output
For monitor
purpose
only
Signals
Notes:
1.
Speed-up/slowdown
on DOM
playback
is optional
and may not be possible
with all
systems. 2.
If the DOM must
can operate
be specified
with a speed-up/slowdown,
the ROT
increment
per DPSCLK
to the DOM.
31
11. Signal
Timing
Relationships
11.1 General Figure
2 shows
relationships three
the timing relationships
between
different
bit-stream
of the first sample sample)
R1PPS,
information
taken
must maintain
between
RCLOCK
rates (fBsi'S) are shown
after the rising a constant
edge
timing
the fCLOCKor fBsl. This guarantees
1PPS, CLOCK
and RBSn are similar.
to illustrate
Table
points
relationship
that the epoch
with respect
for
that the epoch
of the 1PPS tick (the so-called
'TOST'
to 1PPS regardless
of the sampled
change with fCLOCKor fBsl. After the TOST sample, subsequent 2 k CLOCK cycles, depending on the ratio of fCLOCKto fBSl. 11.2 Timing
and BSn; timing The sample
data stream samples
of
will not
are taken every
Ticks
7 specifies
the minimum
Signal 1PPS ALT 1PPS DPS 1PPS R 1PPS ROT 1PPS DOTMON ROTMON
and maximum
durations
of various
Min duration 1 cycle of CLOCK 1 cycle of CLOCK 1 cycle of DPSCLOCK 1 cycle of RCLOCK 1 cycle of RCLOCK Stretched for easy viewin$ Stretched for easy viewing
Type LVDS LVDS LVDS LVDS LVDS TTL TTL
periodic
ticks:
Max duration 500 ns (inverse 2 MHz) No specification 500 ns 500 ns 500 ns ~10 ms ~10 ms
Table 7: Timing-Tick Min/Max Durations 12. Interconnect
Hardware
Specifications
12.1 L VDS Interfaces Three
physical
LVDS
interfaces
are present
1.
DAS-to-DIM 'data interface' pinout specified in Table 8.
2.
DOM-to-DPS
'data interface'
in the DTS:
on an 80-pin MDR connector
on an 80-pin
MDR connector
pinout specified in Table 8. This pinout is compatible connector to allow easy DOM-to-DIM connections. 3.
'Timing
interface'
on a 14-pin MDR connector
specified in Table 9. If the DIM and DOM have a 14-pin MDR connector.
with 4-40 jackscrews;
with the DAS-to-DIM
with spring
are separate
with 4-40 jackscrews;
latch; pinout
physical
as
units, each will
The interfaces all conform to the LVDS differential format as defined by the ANSI/EIA/TIA-644 standard. All connectors are Mini D Ribbon (MDR) with sockets both the transmitting DAS-DIM BS0 BS1 ll
and receiving DOM-DPS RBS0 RBS1 ii
on
equipment. Pin(+) 1 3 it
Pin(-) 2
Comments
4 ii
BS14
RBS14
29
30
BS15
RBS15
31
32
BSI6
RBS16
42
41
BSI7
RBS17
44
43 32
It
tl
tl
tt
t!
II
vB
,I
BS30
RBS30
70
69
BS31
RBS31
72
71
1PPS
RIPPS
33
34
Unused
ROT 1PPS
35
36
PVALID
QVALID
37
38
CLOCK
RCLOCK
39
40
PCTRL
QCTRL
74
73
See 12.1,6 Notes
Reverse-channel
- forward
'0'
permitted
reverse
PDATA
QDATA
76
75
PSPARE1
QSPAREI
78
77
SparesignalI
PSPARE2
QSPARE2
80
79
Sparesignal2
Table 8:MDR-80
control:
' 1' (default)
only
Pin Allocations (Data Interface)
Signal ALT 1PPS
Pin(+) 1
Pin(-) 2
DPSIPPS
3
4
DPSCLOCK
5
6
Undefined (see 12.1.6 Notes)
7.. 14
Table 9: MDR-14 Pin Allocations (Timing Interface) 12.1.1
Reverse
Channel
Due to requirements
Control
of some
use of only uni-directional accommodate
system
signals
the option
designers,
the base VSI-H
in each of the two MDR
that some
reverse-channel
functions
pairs (P/QCTRL, P/QSPARE1, P/QSPARE2) Interface connector in Table 8:
have
P/QCTRL
by the DAS
- a control
signal
asserted
received
specification
connectors.
P/QCTRL=I (default normal direction.
-
P/QCTRL=0:
Ports
state):
no change,
(as PCTRL)
optionally
i.e. all signal
fitted with transceivers
and P/QSPARE2 will operate in the reverse DAS. Thus static two signal 'back channel' becomes Notes:
Data-
or transmitted
lines P/QSPARE in the 'reverse'
by 1
Equipment "spare" Any
not installing
purpose
transmit
for channels
in the
P/QSPAREI
direction, i.e. DPS to DOM or conventional half-duplex
or DIM to operation
the optional
transceivers
to use P/QSPARE1/2
fix P/QCTRL
in the normal
in the default
direction
for any other
as desired.
combination
connected
channels
possible.
state and may continue
2.
signal
the
as follows:
-
1.
three
in the MDR-80
the DOM (as QCTRL) which specifies whether the two spare signal and P/QSPARE2 are in the 'forward' or are allowed to communicate direction,
to
be allowed,
been defined
requires
In order
without
up, will by default
of equipment complication. operate
with and without Any combination
in the normal
(forward
the optional
transceivers
may be
with less than both optioned only)
mode.
33
.
The
tc_ crsc
channels
DAS or DOM. receive state. .
LVDM
(Multipoint)
terminations
No specific below.
12.1.2 If the
Suggested optional
PSPARE
tbr
Table
carry
transceiver
10 shows
Cable
suggested
Signal
line
when
explicitly
automatically
chips
are
commanded
forces
(e.g.
by driving
specifications
the
normal
indistinguishable
channels,
) allow
current
from
but see
capability the clocking timing
(though
the
signal
suggested
described signals
above
signals
into
MDR-14
assignments
is implemented,
normally
assigned
single-
usage
the Data
connector when
Cable must
and
Timing
the
as well).
P/QCTRL="0":
PSPARE 1
TVGCTRL
From DIM
See Notes
PSPARE2
DOT 1PPS
From DIM
See Notes
DPSCLOCKX
To DOM
DPSII'PSX
To DOM
10: Suggested
Cable,
eliminating
be present
Comments
Table
it.
the
to the
Direction
QSI'Af_E2
into
normal
New Assignment
QSI}AP, ti 1
to the
SN65LVDM050/051
double
for the reverse
by the
transceivers
Usage
'reverse-channel'
the Timing
active
cable
is defined
channel
can
become
of the
timing
purpose
reverse
all
ends
Reverse-Channel
1/2 lines
integrating need
only
standard
at both
Net waveform and terminated LVDS. 5.
may
A disconnected
Reverse-Channel
Substitute
for DPSCLOCK
Substitute
for DPSIPPS
Signal Assignments
Notes: 1.
The use of QSPARE 1/2 here DPSCLOCK and DPS [ PPS.
2.
The purpose of DOT t PPS is to allow receive DOT1PPS from the DIM via a TVG
in the
DAS
a l-pps
input
or a control
port
requires
a 1-pps
thnction 12.1.3
are simply
which
Wavelbrm
direct
replacements
(pseudo-random
a DAS otherwise the Data Cable. noise
on the
DAS.
without This then
functions
only)
It also
enables
synchronizing
for the
signals
a 1-pps enables
without
signal to the use of
requiring
the periodic
either
PDATA
signal.
Specifications
Figures 3 through wavefornls. Parameter
5, along
with
Table
1 1, specify
timing
characteristics
of the LVDS
64MHz
! 28MHz
1
I% t{)¢K
31.3
15.6
7,8
tl
0.3T
9.4
4.7
2.3
t2
0.35T
10.9
5.5
2.7
t3
T-t I
21.9
10.9
5.5
t4
0.15T
4.7
2.3
1.2
i5
0.2T
6.3
3.1
1.6
t6
T-t4
26.6
13.3
6.6
t7,t8
_ 0.25
0.25
0.25
0.25
t7,t8
_,
_
°_- N
_: o3 n Q.
(B
80-pin
MDR
connector;
all
_0
LVDS
_Oo
IJ
,,¢ 0
0 _1
m
0
Oo
o
0 0
0
_1
v
.............
"
I
...........
I
,
t2
vi
'_"
t 3
' ___
CLOCK_
-454 mV
I
vi-'q
m, tl
'
I
',
'
'
..........................................................
m/l
454 mV
m/l
I
,
T
r'4 Figure
_,
3: LVDS Transmitter
I
' -"-2-m/l
I
I
OV
I
,
I Output
Eye Pattern
454 mV
Figure
4: LVDS Receiver
Input Eye Pattern
Transmitter Transitions
I
...........................................................
/i i\ _OOmV .................-/-T...................--r_............-i-....ov -L-'-
-L-Ai
--4!
i_
t7 Figure
5: LVDS Waveform
t 200_nV
t8 Transition
Definitions
46
TV15 TV31 TV14 DSQ
TV30 TV13 DSQ
•
•
•
TV29 TV12 DSQ
•
•
•
TV28 TV11 DSQ
•
•
•
TV27 TV10
S D
Q
TV26 TV9 D
Q
•
TV25 TV8
S D
Q
•
TV24 TV7
S D
Note: "S"inputonDflip-flopsis synchronous.
Q
TV23 TV6 DSQ
•
TV22
o
TV5 DSQ
TV21 TV4 DSQ
•
TV20 TV3 DSQ
•
TV19 TV2 DSQ
•
•
TV18
e
TV1 DSQ
1PPS CLOCK
DQ
TV17
INIT
TV0 DSQ
•
TV16
Figure
6: Test-Vector
Generator
Schematic
TVGEN.DRW 000422
47
1 PPS/R
1 PPS_
I
c,oc -I
RCLOCK
LI-IJ-_I-LI-I_-L
-E
TV12
(at CLOCK
pndefined
rate)__l
to
TV12 (at CLOCK/2
luo_fi_d rate_)_J to
[
0
1
1
tl
t2
t3
I I
0
0
0
t4
t_
t6
0
1
1
t_
t2
t3
L
Notes: 1. TV12 bit stream is shown for illustration. 2. The TV data streams have exactly the same timing relationship to CLOCK/RCLOC and 1PPS/R1PPS as actual data streams. 3. The TVG is initialized on every 1PPS/R1PPS tick. The TV value at tO is undefined 4. Starting with tl, the TVG continuously cycles through the 32767-bit TVG sequenc_ until the next 1 PPS/R1PPS tick, at which point the TVG is again re-initialized.
Figure 7: TVG Timing
Relationships
48
Appendix
A: Revision
Revision
1.0, 7 August
History 2000
First issue
49
W_
m .
,=+
"
/
--
2
_//{/
: /
59%x7
'')
f ,-R NASA
Goddard
Space
Flight
Coordinating
Center
Coordinating
Center
Nan O" R.
Center
Report
_/hndenberg
Abstract This IVS
1.
report
to tile
sunnnaxizes
end of 2000,
Coordinating The
NEOS
the
and
Center
IVS Coordinating (National
Earth
activities
forecasts
of the
a_tivities
IVS
Coordinating
planned
Center
fronl
the
activities
of
Operation Center
Orientation
is based
at Goddard
Service),
Space
a joint effort
Flight
Center
and
is operated
for VLBI by the U.S. Naval
and NASA Goddard Space Flight Center. The mission of the Coordinating Center is to provide communications the IVS community and the greater scientific comnmnity and to coordinate long-term
establishmcnt
for the year 2001.
by
Observatory
and information the day-to-day
for and
of IVS.
The web server
for the Coordinating http
Center
is provided
://ivscc.
The IVS web site's home page is organized and Information, and Coordination. Within
gsfc.
by Goddard.
nasa.
The address
is
gov
into three main sections: Service, each main section there are three
Communications subsections, each
of which contains links to tables, files, or other pages. The design of the home page is a "portal" style, which has many links on the top level and minimizes the number of clicks required to reach information.
2.
Initial
Activities
During the period 2000, the Coordinating
beginning with the official inauguration of IVS and Center supported the following IVS activities:
• Directing Board support: (UK), Wettzell (Germany), (USA).
Notes
support:
were published
Maintained
the
on the IVS web site.
IVS web site,
e-mail
lists,
archive files. The e-mail system and the web site arc the primary munication and information services to the IVS community. • Publications: IVS General are available • Master
Published
Generated
schedules for all prior nated VLBI resources • Meetings: held
2000
IVS
Coordinated,
in KStzting,
Greenbelt,
Annual
the first
Annual
Report
in summer,
and
means
web-based
mail
of providing
com-
1999; proceedings
Meeting in spring, 2000. Published the IVS flyer in fall, 2000. electronically as well as in print form.
schedules:
master
observing
schedules
for 2000 and 2001.
years of VLBI sessions, for use by analysts for observing time, Mark III/IV correlator with Local
Germany
MD in February
Report
in December
Coordinated four IVS Directing Board meetings, in Birmingham Paris Observatory (France), and at Goddard Space Flight Center
from each meeting
• Communications
ending
Committees,
in February
2000
support and
of the first
All publications
Set up master
and coordinators. usage, and tapes.
Coordi-
for the first IVS General
Meeting
the second
Analysis
Workshop
held
in
2001.
53
Coordinating Center • IVS Logo:
Worked
logo, which 3.
NASA
with the Directing
Board
and graphic
artist
Goddard
Space
to develop
Flight
Center
the official
IVS
may be seen (m the cover of this publication.
Staff The
staff of the Coordinating
staff and their
responsibilities
Name
Title
Nancy
Director
Van(tent)erg
Center
is drawn
from individuals
Frank
Thomas
Gomez
Allocation
Responsibilities Web and data
base design
Operation
publications Master schedule,
Manager
management,
Web Manager
special sessions support Web server administration,
50%
resource
meetings
maintenance, maintenance,
support,
Publication
Publication
Support Programmer
discussion data center
processing
Latex support _sistance
and
50%
mail
support, session processing mirror site liaison Baver
75%
and
Directing Board support, support, session web pages,
system system
Karen
The
are:
content, meeting Cynthia
who work at Goddard.
scripts, 10%
programs,
and editorial
i Editor 4.
Plans During
the year 2001 the Coordinating
• Publish
the 2000 Annual
• Coordinate vatory
the first Technical
in March,
• Coordinate
the
Tsukuba, • Support
Report
Center
plans
include
the following:
(this volume).
Operations
Workshop
(TOW),
to be held at Haystack
Obser-
2001. second
Japan Directing
General
in February Board
Meeting
and
the
third
Analysis
Workshop,
to be held
in
2002. meetings
in Greenbelt,
MD
(February)
and
Barcelona,
Spain
Centers
to data
(September). • Work and
with the Analysis products
Coordinator
the access
by IVS Analysis
via the IVS web site.
• Work with the Network via the IVS web site.
Coordinator
• Coordinate the 2001 master observing version of the 2002 master schedule.
54
to improve
to improve
schedule
the reporting
of station
and IVS resources,
performance
and coordinate
2000
IVS
data
the initial
Annual
Report
Geod_tisches
Institut
der
Universit_it
IVS Analysis
Bonn
Analysis
Coordinator
A. Nothnagel,
1.
Coordinator
Report
C. Steinforth
Introduction The first 15 months
of working
as the IVS Analysis
Coordinator
have shown
significant
progress
towards making IVS a suecessflll service. Many small tasks have been completed, eventually leading to a number of steps forward worth reporting. Some of the ground work of the IVS Analysis Coordinator had already been laid by the IVS Acting Analysis Coordinators prior to October 1, 1999 (EUBANKS, MA, VANDENBERG, 1999). In the meantime 19 centers have been accepted either as IVS Analysis Centers or as IVS Associate Analysis
Centers.
IVS Terms ToR.
The
distinction
of Reference
(ToR)
between
reducing
these
two groups
the number
Although the ToR calls for regular submissions results from 24 hour VLBI sessions and of Intensive four IVS Analysis • Bundesamt
for Applied
• Astronomical • NASA regularly scientists
• US Naval have
regularly
und Geod/isie
Astronomy
Institute
Goddard
submit around
included
streamlined
in the current
in the initial
version
of the
of a full list of IVS products, so far only EOP UT1 observing sessions are available. By now
Centers fiir Kartographie
• Institute
of classes
has been
(IAA),
of St. Petersburg
Space
Flight
Center
(BKG)
Leipzig,
St. Petersburg, University
(GSFC),
Russia
(SPU),
Greenbelt
Germany
St. Petersburg,
Russia
MD, USA
their EOP results from 24 hour sessions to the IVS Data Centers the world. Up to now the four IVS Analysis Centers and the Observatory submitted
(USNO), UT1
results
Washington from
for use by many
D.C., USA
quasi-daily
Intensive
observations.
USNO teminated its VLBI analysis activities in October 2{)00. Currently all submissions are formatted according to the IERS
Unfortunately,
submission
format
using
one
data line per epoch with correlation coefficients only between EOP parameters of the same epoch. No information on the terrestrial reference frames (TRF) underlying the EOP solutions are submitted as yet. Under a different directory of the IVS data structure the results of a single TRF solution are available which are the basis of the current GSFC EOP solution. The Analysis Centers activities and submissions
have taken great efforts to organize of the results. The regular delivery
their resources is of particular
for regular importance
analysis for the
long term maintenance of consistent series. Currently, all Analysis Centers use a TRF of their choice either by fixing the corresponding values in the least squares adjustment or by transferring the TRF covariance information using pre-reduced normal equations. Starting combination
on October 1, 2000 the individual session EOP results are processed further procedure at the Analysis Coordinator's office in order to generate a combined
in a IVS
EOP product (see section 2). Before the comparison and combination activities of the EOP results could be started a number of obstacles had to be removed in a concerted effort. The data format and
auxiliary
2000
IVS
Annual
information,
Report
although
specified
as standards,
had
to be corrected
in some
of the
55
IVS Analysis Coordinator
Geod_itisches Institut der Universitiit Bonn
submissions. File names and directory structures were reorganized, and Analysis Centers had to be sunnnoned to speed up their submissions. As of today the delay between observations and result dissemination is on the order of 14 days. The combination of the results of different solutions to one combined tmrposes. In the combination process the individual solutions complement leading to a higher accuracy and a higher of analysis centers may change for various occur,
the redundancy
of analyses
product serves several and control each other
reliability. Considering the facts that the constellation reasons or that errors in data and product submissions
is of general
importance:
the more Analysis
Centers
contribute
the smaller the effect of taking out or adding a contributor. This improves not only the individual results but stabilizes long-standing series in general. Any differences can be analysed for the detection of outliers and their causes can be investigated. Another aspect of combination is that more objective error bounds (:an be established which is of particular importance where formal errors are not representative. Although one of the fundamental rules of statistics is to never use an observation more than once, it is still appropriate to produce combined results from submissions of different Analysis Centers. They are using different software packages and/or different analysis strategies by e.g. rejecting different data points, using different weighting schemes, or using different reference frames for station coordinates or radio source positions. to independent and slightly different results.
All this leads to independent
analyses
as well as
An important aspect of carrying out the combinations is, of course, the correct relative ing of the Analysis Centers. For this the use of the scatter in the nutation offset results center which 2.
relative to a combined average is currently is unique for combinations of space geodetic
IVS
Combination
deemed results.
to be the most
appropriate
weightof each approach
Procedure
On December 22, 2000, the availability announced by the IVS Analysis Coordinator.
of the combined IVS EOP products was officially This section provides a description of the combination
strategy being used. In addition, some topics are listed which will need further investigation to refine this strategy or to mitigate known problems of the combination. The combination strategy can be divided into two steps. In the first step, a comparison of the results is carried out to maintain consistency Analysis
Centers
to derive relative weights for the Analysis Centers and to determine biases with a reference series. In the second step the results of the individual
are combined
into one solution
by applying
the weighting
In the following formulae the total number of Analysis Centers contributing is denoted by n, the index i designates the respective Analysis Center (AC). epochs is m. the epochs are labelled by j. In the current following formulae 2.1.
Data
2.1.1.
combination the full varianee/eovarianee the correlations between the parameters
56
and the biases.
to the combination The total number of
is used, whereas for more clarity.
in the
Preparation
Weighting
Factors
For the comparisons analysis
matrix are omitted
factors
the question
,:enters since weighted
arises of how to establish
averages
have to be computed
relative
weights
as a first reference.
for the individual It is quite
clear
2000 IVS Annual Report
Geod_tisches
Institut
that these cannot this purpose the The celestial
der
Universit_it
reference
frame
to the way the analysis
a_s such is very stable
is carried
out, e.g. which
errors
assigned
software
the input
Coordinator
alone. For indicator.
level and deficiencies
used in geodetic VLBI series. offset series can be attributed
and parameterization
for each epoch where
by the Analysis
Analysis
Analysis Centers to be a suitable
at the sub-milliarcsecond
out in the large number of sources to be found in the individual nutation
mean values are computed
to the formal
IVS
only depend on the formal errors assigned by the scatter of the nutation angels de and de appears
of individual sources average Therefore, most of the scatter noise). Initial
Bonn
data
is used
(analyst's
is only weighted
according
Centers. /t
Y_ Pd_ij
dCj sine0
= i=l
d¢ij
sin
eo
n
(1) Pd_
i=1
and n
dcij
Pde_j d_j
-
(2)
i=ln i
with
and Pdei¢ being
Pd,pij
the respective
1
weights 1 Pewit
--
a2¢ij
and
(3)
1 Pdeij
In the next step biases
for each nutation Vd_)_j
--
(4)
O.2 deij
offset and analysis d¢ij
sin co _-
sin co
center
are computed
(5)
d¢j sin co
-
from the residuals:
and Vdeij
=
dcij
-
d_j
(6)
m
E Pdwij ' biasi,d_
sin eo =
j=l
Vd_ij
sin eo (7)
m
F_ p' j=l
d_p_j
and m
t v Pdeij biasi,de
_
deij
J=lm
(8)
E' Pdeij
j=l
where
' Pd_/
and pld_ij are the weights
of the respective '
Pd_ij
residuals, 1
--
12
computed
from (9)
0. d_/) i j
2000
IVS
Annual
Report
57
IVS
Analysis
Coordinator
Geod_itisches
Institut
der
Universit_it
Bonn
and 1 pt
(10)
_ de i j
Grt2
deij
with t2
2
2
ad¢_j = XaCj (ad_,j
)
n
(11)
_, Pd_i_
i=1
and 12
2
O'd_ij
:
2
Xdej
(°d_ij
(12)
n
E Pd_ij
i=1
with the respective
X 2 per degree
of freedom n
Pd¢ij 2 XdCj
V2_pi j sin eo
i=1 =
(13)
n--1
and n
2 Vdeij
Y_ Pdeij
X_e_ -i=1 The
quantity
weighted nutation
X2 is also called
root mean components
variance
of unit
(14)
n--1
weight
(Koch
squared error (wrms) is computed in a root sum squared (rss) sense:
wrm,Si,nu
t =
1988).
for each
wrmsi,dCsine
° -_ WTIt"_8
Prom
analysis
the
center
bias-free
series
combining
a
both
(15)
d_
with j_lPtd¢,j sin e0(vgwi, - biasi,g¢
WrTltSi,d_
sin eo
--
i
sin co) 2
m
771
_ j=l
(16) P_,Jg
and
wrmsi,d_
=
_-I
7¢t
---
(17)
E
j=l
The combined
wrms
of the analysis
centers:
of the nutation
offsets fi-
are then
used to derive
new weighting
factors
wrmsi,nut
for each (18)
wr_rtsnut
where wrmsnut
= --1_--_ wrmsi,nut
(19)
?_ i=1
58
2000
IVS
Annual
Report
Geod_tisches
Finally
Institut
new
der Universit_t
_(,_ew) PdV,¢ and
weights
Bonn
IVS Analysis
Coordinator
_(new) for the
Pdcij
input
data
are
calculated:
(new) _. (old) Pd_&j = JiPd¢ij
(2o)
p(neu,) deij
(21)
and
For (Fig.
fine 1).
tuning,
Table
the
1 gives
process
is then
an impression
Analysis
repeated
of the
Center
A
by
applying
current
Analysis
level
Center
the
new
of agreement
B Analysis
weights of the
Center
to the weighting
input
data
factors.
C
Xp, Yp, UT1,
Xp, Yp, UTI,
dpsi, deps + form. errors
dpsi, deps + form.
,fiP&ij(otd)
:
dpsi, deps Xp, Yp, errors UT1 + form.
errors
-. ! I I I I
weighted
means
!
for dpsi, deps
per epoch
computation
removal
of a Bias for each EOP
of Bias and computation
WRMS
WRMS
dpsi'
of WRMS
depsPer Analysis
Center
combined WRMS for nutation
weight
Figure
2.1.2.
Offsets
Since this
the
users
requirement
offset
series
observations, series be
relative
C04
of the has
are
fairly
polar of the
of importance
to
IERS
taken
uncritical
motion
and
International and
2000 IVS Annual Report
should,
1. Comparison
procedure
C04
combined
to be
factors
series into due
therefore,
be
rely
young
series
Rotation
also
in the
to their
UT1-UTC Earth
will
account
have
on
the
long
history
and
maintained.
(IERS) Tile
stability
process. their
a long history.
Service
term
combination
(e.g. next
direct
step
1996) before
with
series
the
nutation
the
reference
connection
Consistency IERS,
of EOP
While
to VLBI
is considered
to
combination
is,
59
IVS
Analysis
Geod_itisches
Coordinator
Table
1. Weighting
AC BKG
thus, are
the determination computed
from
of offsets data
Universit_it
Bonn
weighting factor 1.06 1.00
IAA
0.90
SPU
1.06
sets of each
der
factors
GSFC
between
Institut
the
individual
individual
Analysis
series
and
Center
the IERS which
cover
C04 series. the
period
Biases from
the beginning of 1999 to September 30, 2000, the date immediately prior to the first epoch of combination. The computation is shown by example for the x component of polar motion. At first, differences between the respective data point of each analysis center and the corresponding
C04 point
are calculated: v_j
The
differences
- xco4d
vx_ are then used to compute
- xq
(22)
the biases: m
Pxij
biasi,x
VXij
= j=l
(23) Pxij
j=l
As long ms no changes in the strategy 2). New biases are computed from
of the solution are introduced the biases are frozen (cf. Table time to time for controlling purposes and may be applied if
necessary. 2.2.
Final
Combination
For each data point the respective bias and weighting factor are applied before average is computed yielding the combined EOP value (Fig. 2). As an example the the combined
x component
of the polar
motion
for epoch j is given
by the following
a weighted formula for
equation
(24):
n
fiPx_j (xij - biasi,x) XJ, combi
_
i=1 i
and for y and UT1-UTC analogously. (27). The accuracy of one combination propagation
(Koch
(2Zl)
n 1
f iPx,j
For the combination of the data point can be obtained
nutation offsets cf. equation by applying the law of error
1988): 2
(TXj,combi
--
n
52 0,x_
(25)
i=1
60
2000
IVS Annual
Report
Geodiitisches
Institut
der
with the X2 per degree
Universit_it
Bonn
IVS
Analysis
Coordinator
of freedom n
fiPxij _.2
2
O,Xj
In equation
:
(24) the biases
[Xj,combi
-- (Xij
--
biasi,x)] 2 (26)
i=1
XXj,comb
i
_--
n
and the weighting
factors
--
1
are regarded
to have
no errors.
In a refined
strategy, which has to be set up soon, these errors have to be taken into account, too. No bias is applied to the combination of tile nutation offsets, only the weighting factors used
are
fiPd_ijdeij dej,comb
i =
(27)
i=ln
E fiPa_q i=1
and for d_ analogously.
The results
of tile combinations
IERS
are regularly
They
are available
Analysis Center C
I
Analysis Center A Analysis Center B
updated.
EOPC04 Xp, Yp, UTI
Xp,form. Yp. errors UTI, ][ +
Yp, errors UTI, +Xp, [brm.
Xp, Yp, errors UTI, + form.
Xp, Yp, UTI perAC L__ F" weighted mean differences fl)r Bias for each Analysis Center |
t
/
[
removal of Bias
]
weighted means per epoch weight factors
¢
I
combined Xp, Yp, UTI per epoch
Figure
2. Combination
]
I
strategy
both graphically and numerically on the IVS Analysis Coordinator's web page via the IVS Home page or directly from http:///miro.geod.uni-bonn.de//vlbi/IVS-AC//index.html. As an example the combined series for polar motion is printed in Figure 3 and Table 2 summarizes the average statistics of the current combination solution.
2000
IVS Annual
Report
61
IVS
Analysis
Coordinator
Geod_tisches
Institut
der
Universit_t
Bonn
0.3
0.2
0.1 tO 0 o 0.0
.__
X
-0.I
-0.2
-0.3
.........
i
O0
........
i .........
0.1
_ .........
0.2
1 .........
0.3
Y pole
0.4
p ......... 0.5
0.6
in arcseconds
Figure 3. IVS combined polar motion
2.3.
Further The
Investigations
strategy
orientation procedures.
• quality
reflects
of the stochastic
control
combination
same data
above
known
Problems
the first steps
towards
a rigorous
parameters. Of course, there are well-known problems These problems can be divided roughly into two groups:
• deficiencies
The
described
and
cannot
combination
of the
current
of Earth combination
model
and redundancy strategy
presented
implies
actually
a violation
process.
This is presently
be used twice in an adjustment
of the
basic neglected
rule
that
the
by treating
the input data of the Analysis Centers as "new" data. The described deficiency can perhaps be mitigated by introducing a kind of correlation between the Analysis Centers since the data from VLBI experiments is limited. The question of the correct relative weighting has to be considered carefully, too. Another task is the implementation
of a suitable
method
for outlier
detection
and elimination
to increase the reliability and robustness of the combined solution. A further extension to the stochastic model will be the estimation of variance-covariance components. Different methods of the estimation of variance-covariance components have to be checked. Furthermore, a rigorous link between EOP and TRF on the basis of SINEX input should be established in a refined combination procedure.
62
2000
IVS
Annual
Report
Geod_itisches Institut der Universitiit Bonn
IVS Analysis Coordinator
Table 2. Current average statistics xp
BKG GSFC IAA SPBU
3.
IVS
Data
One
of the
observing
yp
bias
wrms
bias
wrms
-109 22 87 42
56 66 77 73
20 -25 -133 -147
62 80 75 72
UT1 - UTC bias wrms
dW sin e0 bias wrms
18 -17 -6 -15
-26 8 -8 28
3 3 3 3
key issues
data
of a service
to the IVS Analysis
primary
• Bundesamt
IVS Data
are always
de Paris
Goddard
like IVS is a timely Centers
and
and
as consistent
First
IVS
Analysis
and astrometric
(NOTHNAGEL,
36 60 44 37
Centers
2000).
dissemination
to the users.
of the raw
In this scenario
the
of permanent accessibility requires scheme guarantees that the data at
Center
(BKG)
Leipzig,
Germany
France (GSFC),
Greenbelt
It is noteworthy
the IVS data
that
with
MD, USA this scheme
and the IVS products
and with
the
have been available
strong
worldwide
Workshop
On February 24, 2000 the first IVS Analysis IVS 2000 General Meeting at KStzting on Feb. geodetic
-1 20 -9 -3
at
(OPAL), Paris,
as possible.
reliable
of the results
und Geod£sie
Space Flight
commitments of the Data without interruption.
4.
Centers
fiir Kartographie
• Observatoire • NASA
43 45 51 47
wrms
Centers
IVS Data Centers play an important role since the necessity constant maintenance of the equipment. A careful mirroring the three
de bias
Workshop was organized in conjunction 21-24, 2000. In this workshop the many
with the different
analysis activities were discussed and some basic aspects were coordinated In view of the many tasks to be organized and to be distributed en route
to the establishment of a service covering all products was only a first basic step forward. A second workshop
to be generated eventually this workshop to be held in February 2001 will refine the
initial ideas taking into account the achievements and experience of the first year. During the first IVS Analysis Workshop five IVS Analysis Working Groups were established. However, the activities of the working groups were less enthusiastic than anticipated were established, a fact which will have to be looked at in the next workshop as well. So far only the Analysis Coordinator's office regularly publishes combined Earth
when
they
orientation
parameters. However, other Analysis Centers are encouraged to take up this task in parallel order to establish quality control and redundancy. The comparison with independent series solutions in use.
is a helpful
2000 IVS Annual Report
measure
to reveal
weaknesses
or inconsistencies
of the combination
in or
strategy
63
IVS
Analysis
Coordinator
Geodiitisches
Institut
der
Universitiit
Bonn
Acknowledgements The work of the IVS Analysis Coordinator would not have been possible without the many individuals who submitted data and results or provided support in any aspect of operation. Of equal importance axe those who contributed in the discussions and made all could be realized. We axe thankfill for all these contributions.
suggestions,
of which
not
References Eubanks T.M., C. Ma, N. Vandenberg (1999): Analysis Report, NASA Publication TP-1999-209243, 27-28 Koch K.-R. Berlin Nothnagel
(1988):
Parameter
A. (2000):
Excerpts
Geodesy and Astrometry, MD, 393-396
64
Estimation of the first
2000 General
Coordinator
and Hypothesis IVS
Analysis
Meeting
Testing
Workshop
Proceedings;
Report, in Linear
International
IVS
1999 Annual
Models, VLBI
Springer, Service
NASA/CP-2000-209893,
2000
IVS Annual
for
Hanover
Report
Network Coordinator
NVI,Inc./NASA Goddard Space FlightCenter Network
Coordinator
Report
Ed Himwich
Abstract This report IVS to the end
summarizes the activities of the of 2000. It includes an assessment
over an approximately
1.
Network
12 month
Coordination
The activities
primarily
The
report
forecasts
activities
planned
for the
of data
year 2001.
Activities
of the Network
of network station performance The main effort in network was done
period.
IVS Network Coordinator from the establishment of the network performance in yielding usable
Coordinator
fell primarily
into two areas:
monitoring
and developing station configuration files. coordination was monitoring the performance
by monitoring
the
"ivs-ops"
messages
from
the
stations,
the status
of the stations. correlator
This reports
(both prepass and final), and analyst reports. There were virtually no analyst reports in this period. The various reports were checked. If any problems were reported, they were pursued with the station and cognizant experts. Because this information was reported on a per session basis, it was rather difficult to get a clear view of how any particular station was performing. Consequently, it was decided that a station performance data base that stores the information by station should be developed. This data base hand as an Excel spreadsheet. section below. One of the goals
for network
was started A summary
in the spring of 2000. Currently, it is maintained by of the station performance is presented in a separate
coordination
is to develop
a data
base of information
about
each
site and its configuration. During 1999 an ASCII template of information was developed. Each station can fill it out to describe the equipment and environment of the station. So far about half the IVS Network Stations have completed the form. The completed forms can be viewed from the Station 2.
Configuration
Network
Files link on the IVS Coordinating
Center
web page.
Performance
The station and problems.
performance data base contains a wealth of information about It includes all reports of problems from correlator pre-passes,
station performance correlation reports,
analysts, and stations as well as a history of inquiries made about resolving problems. started in May of 2000 and includes all information since then. There were no analysts
It was reports
except for occasional e-mails about problems processing certain sessions. It was decided that the correlator reports formed the most reliable, albeit not the most timely basis, for monitoring station performance. (Within the data base, the issue of timely response is addressed
by the station
and correlator
pre-pass
reports.)
The coverage
of sessions
in the correlator
reports is somewhat spotty due to delays in processing sessions, the unevenness of the delays, and problems related to the start up of the Mark IV. As of early January 2001 the set of correlator reports in the data base covers many, but not all, of the sessions from November 1999 through December 2000. The data base includes 69 sessions with 388 station days (about 5.6 stations per session
2000
IVS
on average).
Annual
Report
65
Network Coordinator
Any assessment used.
NVI, Inc./NASA Goddard Space Flight Center
of station
For each station
performance
in each session
is somewhat
an estimate
arbitrary,
is made
but the following
of how large
the data
approach
was
loss was.
Each
station day was then assigned to one of the following categories: (A) No data loss (0% lost), (B) Slight Data Loss (1-6% lost), (C) Moderate Data Loss (7-20% lost), (D) Severe Data Loss (2170% lost), and (F) Failed (71-100% lost). Again these categories are somewhat arbitrary. The divide between slight and moderate loss was set so that loss of one channel (7%) was considered moderate. Consequently, the slight category includes mostly some RFI, and short data losses, up to a little less than 90 minutes. The divide between moderate and severe was set so that loss of three channels about 5 hours
(21%) would be severe. This means that the loss of two channels or gaps of up to would be considered moderate. Severe data loss includes loss of three channels or
more, operation with a warm receiver, long data gaps, and other severe any cases where the data from the station is not useful geodetically. categories
will probably
undergo
Using the above criteria, No Data Loss, Loss, 3%, and although this future reports, 3.
some
refinements
the 388 stations
problems. Failure The definitions
includes of these
in the future.
days in the data
base are distributed
as follows:
(A)
48%, (B) Slight Data Loss, 25%, (C) Moderate Data Loss, 12%, (D) Severe Data (F) Failure, 6%. In essence this means that 94% of the station days was usable, statistic ignores the fact that some usable days were significantly degraded. In the the cause of the data losses will be described as well.
Plans During
the year 2001, the plans
for network
coordination
include:
further
use and development
of the station performance data base including possibly making it accessible from the web, encouraging the remaining stations that have not submitted site configuration files to do so, development of a local site survey data base and the development of performance standards. It was recognized in 2000 that it would be useful to develop a data base of site tie information, both for connecting VLBI stations to local monuments, but also between VLBI and other collocated techniques. This will be developed further next year.
66
2000 IVS Annual Report
?, f
zoozooL/o1"
y;/
,/
MIT
Haystack
Observatory
Technology
Technology
Coordinator Alan
Coordinator
Report
Whitney
Abstract The
main
Standard
effort
has been
1.
VLBI After
by both
VSI-S.
at http
Technology
hardware
approved
counterpart, and
of the
Interface
The
://dopey.
IVS and
VSI-H
during
(so-called
the astronomy
specification
haystack,
Standard
Coordinator
specification
was
This
community.
is available
edu/vsi/index,
2000
VSI-H).
devoted
to completing
specification
is now
_,Vork is now beginning
in the
Special
Reports
the
VLBI
complete
and
on the software
section
of this
volume
html.
Interface
18 months
of effort,
the VSI-H
specification
was formally
approved
on 7 August
2000 by
the VSI Technology Coordination Committee. This followed many discussions and many iterations of VSI-H draft specifications, including an international 2-day meeting at Haystack Observatory in January 2000. The specification has been subsequently approved and adopted by both IVS, representing the geodetic community, and GVWG, representing specification is the hardware part of the VLBI Standard
the astronomy community. The VSI-H Interface Specification, which will allow
the transmission of data to and from heterogeneous VLBI Data Transmission VSI goal is to specify a common interface to be compatible with traditional system, network of the VSI must
data transmission and even direct-connect completely hide the detailed characteristics
deal only with the interfaces The following
to the outside
assumptions
were made
• The DTS is fundamentally
be mutually
agreed
• The received
between
and transmitted
to the correlator acquisition must
world.
a receiver
upon
systems. In order to do this, the design of the data-transport mechanisms and
in the development
• The meaning of individual bit streams of sign or magnitude bits associated
Systems (DTS). The recording/playback
and transmitter
of bit streams
is not specified; with particular
normally, a bit-stream will be a stream samples, but the actual meaning is to
the data-acquisition
bit-stream
clock rates
of the VSI specification:
system
and the correlator.
may be different
(e.g.
the playback
rate
may be speeded-up or slowed-down); however all bit-stream clock rates on be the same, and all bit-stream clock rates on transmit must be the same.
• The data-acquisition
time-tag
of every bit in every bit-stream
must
be fully recoverable
with
no ambiguity. Some of the 'features' • definition
of a 1 Gbit/sec
1. 32 parallel 2. 32 MHz • One standard • Standardized
2000
IVS
Annual
of the VSI-H
Report
'Quantum
specification
include:
Channel':
bits streams (extensions
to 64, 128 MHz for 2, 4 Gbit/sec
80-pin
connector
electrical
and
per 'quantum
timing
'quantum
channel')
channel"
specifications
67
Technology
Coordinator
MIT
• Low-voltage
differential-signal
• Method
of time-tagging
• Built-in
Test-Vector
• Model-delay
data
is totally
capability
to simplify defined
translation
Cannon
• Brent
DRAO,
• Dick Ferris-
ATNF,
• Dave Graham • Tetsuro
Popov
• Sergei
Pogrebenko
• Jon Romney • Ralph
by VSI-H
connection
to correlator to new systems
copying) part
of the VSI specification,
dubbed
VSI-S.
members of the VSI Technology to reality:
We hope
Committee
for
Canada
Germany Japan
- NAO,
• Misha
to DTS and not specified
Canada
- CRL,
• Nori Kawaguchi
interface
Australia
- MPI,
Kondo
Observatory
capability
thanks to all the other the VSI-H specification
- York University,
Carlson-
signal
to ease transition
(i.e. tape
I wish to extend special many efforts to bring
• Wayne
internal
direct
Work is now beginning on the software to complete this effort by the end of 2001.
their
electrical
Generator/Receiver
• Two levels of compliance • Easy media
(LVDS)
Haystack
Japan
- ASC, Russia - JIVE,
- NRAO,
Spencer-
• Rick Wietfeldt
U.S.
Jodrell, - JPL,
Netherlands
England
U.S.
The success of VSI-H may be measured in part by the fact that at least three institutions are already developing equipment designed to be in compliance with the VSI-H specification. The full 30-page VSI-H specification, along with an interesting historical chronology of its development, reprinted in this volume and is available at http://dopey, haystack, edu/vsi/index .html. 2.
Other Other
is
Activities planned
and ongoing
activities
in the technology
coordination
area
are:
1. Formation of a few small subgroups with interest in particular technology areas. The members of these subgroups will be drawn from IVS technology centers and other experts in the field. These sub-groups, interacting primarily via e-mail, will be asked to develop a list of concerns and goals and to suggest the steps needed to achieve them. The VLBI Standard Interface
68
group
serves
a.s a prototype
for this type of activity.
2000
IVS
Annual
Report
MIT Haystack
2.
Observatory
Coordination nology field,
3.
As
VLBI
be invited
ongoing technology
2000 IVS Annual
index
Ideally,
material.
will an
of an
areas.
referenced
Technology
Report
this
of published
papers
and
will be a Web-based
All IVS
technology
memos
index
development
with centers,
in all links
of the
relevant
Coordinator
VLBI
tech-
to electronic
versions
of the
as well as other
experts
in the
to contribute.
activity,
promote
at international
and
encourage
meetings
and
inclusion
of topical
sessions
on
advanced
workshops.
69
j,_
_r 7
7-_;'-J
/'_,,., ":c_
U
U/
,/Y_1
Geodetic
Survey
Division,
Natural
Resources
Canada
Algonquin
Algonquin
Radio
Mario
Radio
Observatory
Observatory
Bdrubd,
Calvin
Klatt
Abstract The Algonquin north of Ottawa partnership The
Radio Observatory (ARO) is situated in Algonquin provincial and is operated by the Geodetic Survey Division of Natural
with
the
antenna
is a key site Station. This
report
Space
is involved
in the
ongoing
summarizes
Figure
1.
Canadian recent
Laboratory,
number
CRESTech.
of international
$2 developments. activities
1. Algonquin
geodetic The
at the
Algonquin
Radio
Observatory
ARO
VLBI is the
Radio
experiments most
sensitive
each
year and
IVS
Network
Observatory.
46m
Antenna
Overview The
ARO
46 m antenna
involved as early in Prince Albert,
2000
Geodynanlics in a large
park, about 250 km Resources Canada in
IVS
Annual
was used
in the
first successful
VLBI
experiment
as 1968 in geodesy, when the baseline length between Saskatchewan was measured to be 2143 km (sigma=20
Report
the ARO m).
in 1967 and
was
and a telescope
73
Algonquin Radio Observatory
The
GSD
also maintains
Geodetic Survey Division. Natural Resources Canada
a permanent
GPS
monitoring
station
at Algonquin
which
is used
by all IGS Analysis Centers as a fiducial reference. Satellite laser ranging and absolute gravity observations are also available for the site which is located on the stable pre-cambrian Canadian Shield. Local site stability has been monitored regularly using a high-precision network. 2.
Antenna
Improvements
In order to improve of the antenna control This antenna antenna position. operations. The
antemla
the operational performance systemn which wa._ completed
of Algonquin, in 1997.
GSD undertook
a major
upgrade
control system still uses the original azinluth and elevation encoders to deternfine We are in the process of upgrading them in a way that should not affect scheduled field system
was modified
to allow satellite
tracking.
The ARO is currently using a Mk3 VLBI system (on long-term loan from NASA) and we expect to upgrade to Mk4 early in 2001. ARO is equipped with an $2 data acquisition system and recording terminal and has played a crucial role in testing and development of the Geodetic $2 system. We are developing an L-band receiver useful for reception of GPS signals.
for bi-static
radar
Figure 2. Fox at the Algonquin
3.
General • Latitude • Longitude
applications.
This
staff h(ms¢,
specifications : N 45 57 19.812 : E 281 55 37.055
• Elevation
: 260.42
m
• Reflector
: 46 m diameter
with first 36.6 m made
of 0.(;31 ,,,,., :-_...............
receiver
may be
Geodetic Survey Division, Natural Resources Canada
Algonquin Radio Observatory
m of steel mesh. • Foci : S and X band • Focal
length
• Focal
ratio
• Surface
accuracy
• Azimuth
• Receiver
: 10 degrees
: S and X cryogenic
equipment
: MkIII
standard
• GPS receiver 4.
Antenna
The network
capability
with 3 m elliptical
subreflector.
0.5 for solid surface. and
0.64 for mesh.
(10Ghz)
per minutes. per minutes. receiver.
with thick
$2 data
• Time
and
at 3 cm wavelength
: 24 degrees
speed
version
Gregorian
focus)
= 0.4 for full surface
: 3.0 arcmin
• PCFS
focus.
: 0.32 cm for solid portion
speed
• Elevation
• VLBI
: 18.3 m (prime : f/D
• Beamwidth
at prime
acquisition
tape
drive.
To be upgraded
and recording
to MkIV
in 2001.
terminal.
: 9.4.13 : NR Maser : Rogue
Survey
antenna is surrounded by a high stability network made of thirteen concrete piers. This has been precisely measured five times to obtain the geodetic tie between the VLBI, the
GPS and the SLR reference
points
with a precision
of a few ram.
The VLBI
antenna
a special indirect survey since the reference point cannot be accessed We have recently re-measured the network. In addition to tying
directly. GPS and
will attempt
angle.
to study
antenna
deformation
Figure 3. Rapelling
as a function
of elevation
off the Algonquin
46 Ill Antenna
SLR
itself requires to VLBI,
we
Algonquin
5.
Radio
Observatory
Algonquin
Geodetic
Survey
Division,
Natural
Resources
Canada
Operations
A new GSD staff member, Anthony Searle, has joined the VLBI group at GSD and has been assisting with experiment operations. Algonquin Radio Observatory is involved in several international VLBI networks. We summarize below the geodetic
VLBI
activities
in the reporting
period.
A number of additional experiments have taken place in recent years at ARO. 1999 ARO was used to transmit high energy pulses to assist in the characterization
In September of sensors on
board satellites. ARO "Polar Bear Network".
as part
In 2001, We anticipate Interferometry)
the
ARO
also participates is scheduled
in weekly
that it will also participate S2-based experiments. Experiments
Experiment NEOS-A
76
in international
Type
Performed
NEOS
in 10-20
March
March-December 10
astronomical experiments CGLBI
observations plus
(Canadian
1, 1999-December
1999
January-December 31
CORE-A CGLBI
21 6
6 17
CORE-B CORE-1
6 0
3 6
NAVEX CRF
2 1
0 1
12 CORE Geodetic
of the
experiments. Long
Baseline
31, 2000 2000
2000
IVS
Annual
Report
2_oOZ.oo L:, :,,
/
Centro
de RAdio
Astronomia
e AplicaqSes
2000
Activities
Pierre
Kaufmann,
A.
Espaciais,
CRAAE
(Mackenzie,
Report
Macilio
INPE,
USP,
of Fortaleza
Pere/ra
de Lucena,
UNICAMP)
Station
C1audio
E. Tateyama
Abstract This
report
Espacial
do
Ap|icaqSes period
1.
summarizes Nordeste),
Espaciais)
starting
VLBI
Fortaleza
participated
activities CE,
in agreement
March
Geodetic
the Eus_bio,
1, 1999
performed Brazil,
with
INPE
and ending
at Fortaleza
managed
by
(Instituto
December
Nacional
in 123 geodetic
VLBI
experiments
and
91 19
CORE-B
08 1
5. Repairs decoder system,
of a new and
6. Creation 3.
GPS
updated
of an english
below:
heads
of the tape
recorder.
card, high power amplifier,
version
DC motor
FS computer.
refrigerator
circuits,
of motor-generator
modules,
of the cryogenic or systems:
system.
Mark
III video
converters,
group,
and the cryogenic
Mark
III
axis, UPS battery hydrogen maser,
system.
of web site (http://www.roen.inpe.br)
about
ROEN
activities.
Operation operated
regularly
all the
days.
Data
were
collected
and
Research
Continuation of Washington progresses obtained on structure
2000
in the table
module, Mark III power supply module II, DC motor of elevation monitoring system of receiver, noise calibration diodes controller,
The IGS network GPS receiver uploaded to the IGS computer. 4.
as detailed
Activities
of magnetic
of the cold-head
on the following
the controller
e
in the time
01
Maintenance
and alignment
4. Replacement
Espaciais),
04
2. Antenna drives electrical alignment including controller and tachometer for the elevation antenna axis. 3. Installation
Observat6rio Astronomia
of Sessions
NEOS-A IRIS-S
CRF
1. Replacement
de Pesquisas
RAdio
de RAdio
31, 2000.
Number
C ORE-OHIG
Development
(ROEN:
(Centro
Observations
Experiment
2.
Station
CRAAE
IVS
Annual
Report
correlator of source
data analysis 1803+784.
on various
celestial
sources.
Significant
77
Gilmore
Creek
Geophysical
Observatory
Gilmore
NASA
Creek
Geophysical Rich
Goddard
Space
Flight
Center
Observatory
Strand
Abstract The Gihnore
following report provides a general technical description and Creek Geophysical Observatory located near Fairbanks, Alaska.
Figure 1. NOAA/NASA
1.
GCGO
at
Data Acquisition
and Geophysical
operational
Observatory.
overview
Fairbanks,
of the
Alaska
Fairbanks
Gihnore Creek Geophysical Observatory (GCGO) is located 22 km NorthEast of Fairbanks, Alaska. The observatory is co-located with the NOAA weather satellite command and data acquisition station. The station sits oll an 8,500 acre reservation that is mostly undeveloped wilderness. Ten antennas are in operation. The GCGO telescope can be seen in the photo as the last antenna on the right
in the valley.
GCGO
wa_s instrumented
by NASA's
Crustal
Dynamics
Project
in the
mid 80's for the Alaskan mobile VLBI campaign and used as the base station for those geodetic measurements [1]. The GCGO is part of the NASA Space Geodesy program in cooperation with the U.S. Naval Observatory. Table
1. Address
Gilmore
of GCGO
Creek
NOAA/NESDIS 1300 Eisele Fairbanks, http
2.
Technical The
43.81288"
78
Parameters
26 meter and
://w_.
Fairbanks,
Observatory
FCDAS Road
AK 99712 fcdas,
noaa.
gov
of GCGO
telescope,
Longitude
near
Geophysical
Monument
Number
E 147 ° 29' 42.18552"
4047, Height
X-East 306.418
Y-North, meters
Latitude
is hydraulically
2000
N 64 ° 58' operated
IVS Annual
Report
_
"_
NASA
Goddard
Space
and controlled
Flight
Center
by a Modc()mp
Gilmore
computer
system
(see table
Creek
Geophysical
Observatory
2). The DAT rack is a VLBA
terminal
and recorder (thin tape). The X/S band microwave receiw_r has a cryogenic low noise front end. VLBI Field System version 9.4.14 is used with a PC. Hydrogen Maser Nit 5 is the time standard with an HP Cesium software running
for tile telescope
computer.
A CNS (TAC)
receiver
by the TAC32
for GPS offset mea.surements. The station also runs two NASA/JPL Rogue receivers 8100 JPL VO5 scintillation software. UCLA maintains the HIPAS receive system located in
the GCGO.
The Institut
is located
near
3.
of the
Staff
Geographique
the NOAA
VHF
operates
their new DORIS
GCGO is co-located with the NOAA data Budd. The site is operated by the Lockheed
acquisition Technology
facility. Services
Lockheed
Lockheed
Manager
Creek
in France
facility,
and Roger
Kermes,
Operational
Caskey are assigned to GCGO technical staff with T. Knuutila, Eubanks assisting. The telescope hydraulic system is maintained F. Holan.
Figure
Status
GCGO year 2001.
of Gilmore
Creek
2. GCGO
Ops
Geophysical
beacon
that
building. Alaska
Project
Gilmore
National
transmitter
Fairbanks,
4.
is monitored
crew
Knuutila,
Caskey,
The NOAA Manager is Jim Group with Doug Ooms as Manager.
R. Strand
and S.
Z. Padilla, H. Grotsema, and D. by M. Meindl, A. Sanders and
Strand
Observatory
will be observing eight sessions per month oil average, with 102 sessions scheduled for We observe NEOS every other week and IRIS (race a month. CORE observing with
R&D, APSG, this reporting
CRF and Survey completes the program. Several dewar swaps were made during period. One 28V DC power supply failed in the DAR. The major data loss was
2000
Report
IVS
Annual
79
Gilmore Creek Geophysical Observatory
the
failure
development testing.
of the
Y axis
continues
hydraulic
NASA Goddard Space Flight Center
pump
by Ed Himwich,
on the
Table 2. Technical parameters Parameter
feed of main
agency
Field
DAT racks
System
software
and telescope
for
NOAA/NASA 1962 primary focus 26 meters
reflector
focal length surface accuracy X Y mount
in Aug 2000.
of the GCGO radio telescope for geodetic VLBI. GCGO
owner and operating year of construction receiving diameter
telescope
NVI, Inc., using the station's
10.9728 meters 889 mm rms
of reflector
1 degree
S-band
per second
2.2 - 2.4, GHz 62K
Tsys SEFD(CASA)
650 Jy
G/T
35.3dB/g
X-band
8.1 - 8.9, GHz 58K
Tsys SEFD(CASA)
550 Jy
G/T
44.5 dB/K
Table 3. VLBI observing at Gilmore Creek between 03/01/98 and 03/(}1/99. Year 1999 Experiments assigned to GCGO - 93 Observations scheduled - 23817 Observations recorded - 23353 Efficiency
- 98.05%
Year 2000 Experiments assigned to GCGO Observations scheduled - 20613 Observations
recorded
Efficiency-
5.
- 67
- 19605
95.11%
Outlook Increased
observing
for 2001 is scheduled.
References [1] C.Ma,J.Sauber,L.Bell,T.Clark,D.Gordon,W.Himwich, and J.Ryan Measurement of Horizontal _[otion in Alaska Using VLBI 1990, In:Journal of Geophysical Research, vol 95, No.B13. Pg 21991-22011. December 10,1990
•
80
n_
2000 IVS Ammal Report
•
//"
i
200
NASA Goddard
Goddard
Space Flight Center
Goddard
Geophysical
and
"7 L Ny
of the infrastructure
and
106
VLBI antenna at the Geodetic at the scheduled level. Several stal_ have occurred. Considerable and GPS campaigns on the local
g(_()(le-
geophysical VLBA/RDV,
by means
(if a con-
and GPS. This so-called an area of about 50 km detailed
description
of the
2000 IVS Annual
Report
Geodetic Institute, Norwegian Mapping Authority
geodynamic
setting
and other
details of the VLBI The observatory
Ny-/_lesund 20 metre antenna
observational
activities
antenna, see [2]. participates in the Large
at the observatory,
Scale Facility
(LSF)
see e.g.
Ny-/_lesund
[1]. For technical 1 In the context
of this EU-funded programme, 11 research projects have been carried out in the report period at the observatory with participants from several European VLBI groups. For more details, see [3]. 2.
Staff
Related
to the
Space-Geodetic
Observatory
Table 1. Staff related to the operation Manager: responsible,
in Ny-]klesund
of the VLBI in Ny-._lesund.
Honefoss:
Section Station
Rune I. Hanssen Svein Rekkedal
Ny-/_lesund:
Station manager: Permanent staff:
Helge G. Digre David C. Holland
Rotation
Roar Kihle Kari Buset
H0nefoss:
group:
Bente
(05.1999
R. Andreassen
Kjetil Pdngen Tom Pettersen 6 months
The "permanent" contracts. Expecting on a yearly
contract
Nils Petter
staff at the observatory an increase in experiment
contract
in May 1999 (Table
(only one shift)
(only two shifts)
Rognstad
(10.2000-03.2001)
is employed on the basis of renewable one-year activity for 2000, an extra person was employed
1). With
in 2000, this contract was not renewed. The four members of the rotation group
- 04.2000)
the lack of correlator
have
or had
permanent
capacity positions
reducing
activity
at the Norwegian
Mapping Authority (NMA). The contract period is three years ending in June 2001. Each member spends 3 months at a time in Ny-/_lesund. It was planned that each member would serve a total of 9 months at the observatory. However, one member resigned from NMA, while another one is no longer available due to internal change on a temporary basis to fill the gap. 3.
Status
of the
VLBI
Antenna
of duties.
Therefore,
a new staff member
was employed
in Ny-/_lesund
The overall operation of the VLBI antenna in the report period has been smooth, though some periods posed more problems than normal. The antenna participated successfully in 77 experiments, while for two experiments participation was unsuccessful due to technical problems. out.
A number of more or less routine upgradings, For example, the maser had its scheduled
maintenance and repair operations were carried bi-annual maintenance check in June 1999. The
field system is now FS 9.4.17. The TAC system has been upgraded to a CNS TAC with monitor, counter and computer. The azimuth gears on the antenna have been checked and repaired. The azimuth brakes have been renovated and are working again. The Peltier elements on the antenna were checked in summer 2000 and worn fans were replaced. In autumn, both Peltier power supplies had
to be repaired
after
failures.
In the helium
system,
the cold head
was replaced
in June
1999,
1see http://www.npolar.no/nyaa-lsf/.
2000 IVS Annual Report
107
Ny-/klesund 20 metre antenna
and the compressor
Geodetic Institute, Norwegian Mapping Authority
in November
2000.
A number of more serious crashes and break-downs happened, which partly are due to a more rapid ageing of parts in the severe weather conditions at the observatory. Problems were caused by fading
and eventually
disappearing
antenna
signals.
for these errors, it was found that all the signal link. The cables have been repaired temporarily replacing them by new pieces of cable.
After
eliminating
cables were broken by cutting away
When one of the running encoders caused increasing problems, encoder was defective. The spare encoder returned from repair replace one of the working getting the encoder signal. cable out of the encoder.
the connectors
as a source
or damaged in the elevation the bad pieces of cable and
it was discovered that the spare after 3 months just in time to
encoders, which died totally. Recently, there were severe problems in The source for these problems was located in a short circuit in one
The crash of a rather new hard disk in December resulting in the setting up of a new back-up procedure
1999 happened for the disks.
In the often severe weather conditions, safety of staff during particular attention. In particular, a safety report was written been acquired to make the manhole in the antenna safer. The problem of radio interference (RFI) Ny-/_lesund. The VLBI antenna is sheltered
at the worst
possible
time,
operations on the antenna requires in spring 2000, and equipment has
appears to be mounting even at the remote location of from RFI from geo-stationary satellites by mountains
to the south. However, local activities of other research institutes and the operator of the research town are increasingly in conflict with the condition of radio-quietness imposed on Ny-Alesund. For example, the operator of Ny-/_lesund, Kings Bay, operated a local wireless LAN-net in the 2.4 GHz
area
from February
to June
2000.
environmental quality of radio-quietness to all other groups active in Ny-/_lesund. 4.
Site
surveys
and
other
NMA
is actively
by exploiting
working
legal regulations
to protect
the
important
as well as regular
contacts
activities
In summer 1999, a small instrument house was built above the existing stable platform previously used for absolute gravity measurements. This house was required for the superconducting gravimeter (SCG), which was installed there in September 1999 by Professor Tadahiro Sato, Earth Rotation
Division,
National
Astronomical
Observatory,
Japan.
Daily
operation
of the instrument
is provided by the station staff, while major maintenance work such as annual refill of liquid helium is carried out by visitors of the Japanese team. After some minor initial problems, the instrument is running smoothly via Internet.
and providing
high-quality
data.
The data
is accessible
to the Japanese
team
Prior to the building of the house, two GPS receivers (SATREF and NYA1) were operated on steel masts mounted on the gravity platform. For the time being, NYA1 is continuing to operate there. In addition, a semi-permanent receiver was set up at one of the pillars in the control network in order
to monitor
any changes
in NYA1 due to the building
activities.
In 1999, a roof was built on an existing foundation about 300 m to the north-west of the VLBI and IGS site (No. 2 on Fig. 1). This new construction provides an appropriate environment for continuous GPS sites. In the centre of the large ground floor room, there is a 4x4x4-meter pedestal with concrete walls, well insulated to reduce any temperature effects. Inside the pedestal, a data room
108
is located,
which
is connected
to the net in the main building
by a fibre optic
cable.
On top
2000 IVS Annual Report
Geodetic Institute, Norwegian Mapping Authority
Ny-._lesund 20 metre antenna
of the pedestal, a stable tower reaches through the roof as the monument for GPS antenna. Among others, a GPS receiver of the GFZ, Potsdam, has been installed at this new location, which contributes to the low-latency network supporting Several LSF projects provided contributions relevant antenna
was
installed
permanently
on the
VLBI
antenna.
the CHAMP mission. to the IVS goals. In particular, Whenever
the
antenna
a GPS
is in Zenith
position, the GPS data can be used to monitor the tie between VLBI and GPS directly. The VLBI antenna has been surveyed with classical methods twice, providing accurate coordinates of the antenna reference point. The inner control network was reobserved with classical techniques by visiting groups in 1999 and by NMA staff in 2000. Absolute gravity measurements were carried out in summer 2000 providing a calibration of the SCG and, additionally, a remeasurement of gravity after initial measurements in 1998. NMA carried out GPS campaigns on the inner and outer network in 1999 and 2000. Together with the campaign on the outer network in 1998, the analysis results show a stability of the network on the 1 mm/yr level, except for one pillar which apparently 5.
is moving
[3].
Outlook
In 2001, the observatory will participate in the CORE-3 experiments as well as other experiments such as the VLBI Europe once. A number of repairs, maintenance, and upgrades are planned. For example, the bi-annual maintenance of the maser is due in summer 2001. The FTS 8400 will be retired and shipped back to Honeywell. The repair of the azimuth 1 antenna brake was temporary and some parts need to be replaced. The elevation brakes need to be checked, and all signal cables will be replaced in the summer. A re-routing The azimuth
in the elevation link area will be considered. The new encoder will arrive in spring. encoder then has to be sent to the manufacturer for check. The formatter will be
upgraded to be able to handle the next Linux version.
the CORE-3
experiments.
The
Field
System
will be upgraded
to
Concerning station staff, the experience made with the rotation group arrangement will be evaluated. A decision concerning future employment schemes for the staff at the observatory will be made on the basis of this experience. References [1] Plag, H.-P., 1999: Measurements of vertical crustal motion in Europe by VLBI. Station report for Ny/_lesund, Norwegian Mapping Authority. In Schliiter, W. and Hase, H. (eds.): Proceed. 13-th Working Meeting of European VLBI for Geodesy and Astrometry, Viechtach/Wettzell, February 12-13, 1999. Bundesamt fiir Kartographie und Geodiisie, Frankfurt, 65-77. [2] Digre, H. G., Rekkedal, S., Holland, D. C., Hanssen, R. I. and Plag, H.-P., 1999: NYAL Ny-_lesund 20-metre antenna. In Vandenberg, N. R. (ed.): International VLBI Service for Geodesy and Astrometry Annual Report 1999. NASA, Greenbelt, MD, USA, 80-84. [3] Plag, H.-P., Bockmann, L., Kierulf, H. P., Kristiansen, O., 2001: Foot-Print Study at the SpaceGeodetic Observatory, Ny-/_lesund, Svalbard. In Tomasi, P., Mantovani, F., and Perez-Torres, M.-A. (eds.): Proceedings of the 14th Working Meeting on European VLBI for Geodesy and Astrometry, Castel San Pietro Terme, Sept. 8 - Sept. 9, 2000. In press.
2000 IVS Annual Report
109
• .
: J
3
J German
Antarctic
Receiving
Station
German
O'Higgins
Bundesamt
Antarctic
Receiving
Andreas
Reinhold,
fiir Kartographie
Station
Reiner
und
Geodgsie
O'Higgins
Wojdziak
Abstract Ten VLBI sessions of 24 hours have campaigns. A H-maser failure stopped Modifications PRARE, 2001.
1.
of the timing
etc.)
continued
Observation
system
by a TAC
to provide
Campaigns
been observed successfully the last experiment. The
at
data.
have
The
been
upgrade
O'Higgins
done.
The
to MkIV
during the last three Antarctic local ties have been controlled. collocated
is planned
geodetic for the
systems spring
(GPS,
campaign
1999/2000
During the period from March 1999 to December 2000 three VLBI observation campaigns were organized at the German Antarctic Receiving Station (GARS) O'Higgins by staff members of BKG (Federal Agency for Cartography and Geodesy) in cooperation with the colleagues from DLR
Figure
(German
1.
Antarctic
During
Schmitt spring
Aerospace
Island time
the three
Center
with October
campaigns
the
- responsible
Chilean
base
for SAR Data
and
the
annexed
Acquisition).
German
station
O'Higgins
during
the
1999.
at O'Higgins
altogether
ten 24-hour
VLBI
experiments
were car-
ried out. The observations were mainly focused on the special IVS CORE O'Higgins (COHIG) experiments, namely the experiments COHIG 7 to COHIG 13. In addition the O'Higgins telescope was involved in IRIS South 144, 147 and 155 experiments. Due to a H-maser failure the IRISS 155
110
2000
IVS Annual
Report
_j
Bundesamt fiir Kartographie und Geod_isie
experiment the maser
German Antarctic Receiving Station O'Higgins
had to be interrupted after about 14 hours vacuum system was broken and the H-maser
All the observed analysis for station
Status
of VLBI
and
There
were no major
Other
changes
were conducted
Geodetic in the VLBI
the station
timing
system
had
equipment
between
the various
systems
to be modified.
at O'Higgins
stably Since
and
were used in various evaluations. Syowa,
which
is
station
since 1999. The
with
November
respect
to the special
1999 the station
sync
is
frequency standard HP5061 failed. It is HP 5071 during the year 2002. point was repeated. No changes in the station
were detected.
Figure 2. The VLBI Antenna at O'Higgins, in front the GPS-Antenna protected by different radomes (October 1999).
2000 IVS Annual Report
of
station
of the O'Higgins
worked
realized by a TAC-GPS tracking system. The Cs-atomic planned to replace it by a new cesium frequency standard In January 2000 the survey of the antenna reference eccentricities
with the JARE
ion pump
Equipment
main components of the VLBA/MkIII equipment Antarctic conditions with sufficient quality. Only
The external
experiments could be correlated successfully and the data position determinations and Earth Orientation Parameter
At the end of 1999 first experiments the second VLBI station in Antarctica.
2.
of observation. lost lock.
and the PRARE
ground
unit
111
German Antarctic Receiving Station O'Higgins
The additional interruptions the station
geodetic
systems
in the continuous is unmanned.
The PRARE
ground
collocated
data
The permanent GPS tracking data and additional information DOMES No. 66008M001.
Bundesarat fiir Karto_raphie und Geod_ie
occurred
are working - especially
continuously. during
those
Sometimes periods
when
system, a TURBO ROGUE, is included in the IGS network. The can be found under the ID character OHIG and under the IERS
unit at O'Higgins
can be found
Since February 1999 a new tide gauge the sea surface level around O'Higgins. 3.
in O'Higgins
acquisition
system
under
provides
COSPAR
continuously
No. 7710. data
of the variations
of
Outlook
The upgrade of the O'Higgins station to a VLBA/MkIV ment and the field system 9.xx is in progress. All the necessary
racks,
parts,
computers
and
station
tools are shipped
including
the thin tape
to the station
there during the first weeks of the year 2001. It is planned to install and to test all the new systems at the station during 2001 in January/February. The first experiments employing the new equipment the weeks 7 and 8 of the year 2001. Regarding the installation of TIGO
in Conception
(Chile),
and
equip-
will arrive
the first campaign are scheduled for
it has to be pointed
out
that
the
importance of O'Higgins VLBI station (GARS) as a reference point close by will increase and common observations will improve the results tremendously. Therefore, it is planned to continue the campaigns
112
in the next years,
if possible
twice a year.
2000 Ivs Annual Report
2..50 /
56 r!.i '0
5 55"7o!
/
Onsala
Space Observatory
The Riidiger
IVS
Haas,
Onsala
(OSO)
Network
Gunnar
Station
Elgered,
Onsala
Space
Sten Bergstrand, Lubomir and Karl-like Johansson
(_SO) I
Space Observatory
Observatory
Gradinarsky,
Borys
Stoew,
Abstract We give a short overview of the status of the Onsala Space Observatory in its function as an IVS Network Station. The activities during 1999 and 2000, the current status, and future plans are described.
1.
Introduction The
extent the
IVS in the
station.
[1] with
2.
Network last The
the
and
IVS staff
RDV
annual
during
has 1999
been
and
due
to usage
shipped
experiments
Exper. EURO47 RDV13 RDV14 EURO48 RDV15 CB602 RDV16 EURO49 CB603 RDV17 EURO50 CB604 CB605 EURO51 EURO52 CB606
Date 990201 990308 990415 990426 990510 990519 990622 990629 990630 990802 990816 99O823 991004 991011 991013 991018
2000 IVS Annual
Report
Network
left
in the
the
only
(OSO)
minor Station
has
been
described
to some
changes
in the
technical
setup
remained
the
same
of
as reported
in
observatory.
recorder due
A PROM
1). Two
experiments
errors
tape
problems
speed
lost due to pointing tape speed problems
CORE-B,
experiments
have
During
vacuum
for some
period.
in the
formatter
the
necessary
and
was
at the
Remarks (problems) high parity errors
high parity
VLBI-series
respectively. to a problem
with
Observatory
VLBI
geodetic
[2] (see Table
were
mode.
1. Geodetic
are
IVS
problems,
of wrong
to us by Haystack
Table
There
the
involved
2000
problems
observing
Observatory
observations
due to encoder
CORE-3
Space
[1].
BystrSm
Rune
and
fanout
report
that
problems two
Onsala
with
VLBI
observatory
at the
associated
exception
Geodetic The
Station
problem
firmware
installed
Onsala
Space
Exper. RDV18 RDV19 EURO53 EURO54 RDV20 EURO55 EURO56 C3001 EURO57 C3002 EURO58 C3004 C3005 EURO59 C3006
been
one experiment The
update
successfully
Observatory
Date 991220 000131 000127 000207 000313 000316 000515 000712 000807 000823 000904 001018 001101 001207 O01213
CORE-3, lost
due
we had weak
with
to solve
during
Remarks
to pointing
tape
recording
$1 channels
firmware during
EUROPE
the
this
during 1-bit,
problem
November
1999 and
1:2 was
2000.
2000.
(problems)
high parity errors formatter jump
on one tape
high parity errors some recording problems lost due to encoder problems two bad tracks channel S1 weak channel S1 weak
113
Onsala
3.
Space
Observatory
Monitoring
(OSO)
the
Onsala
Performance
of the
VLBI
Space
Observatory
(OSO)
System
The log file of each experiment is analysed in order to detect problems and fix them accordingly. The cable delay, the difference between GPS and formatter time, the physical temperature in the dewar for the front end HEMT amplifiers of the receivers, the measured system temperatures and the parity
errors
are monitored
some transient problem are ongoing to identify
(see figures
1 3).
with tracks numbers the reasons.
. 13'51
.
12.4[
_
12.2|
-
EURO54
.....
.
..
The
31-33
• .."_
• ". "_,.
monitoring
in recent
":
of the parity
experiments.
indicates
investigations
_
_ss
.. M-:-_:
°.=1_,¢..
errors
Currently
x
x_
40
25 10
200[ _"
5.4[
o..'..
_. s.2t
.....
-.
.
• 40 i13"5
I_
x
"
I _x
t3.3
×Xx×X×Xxxxxxx
×
lO
L 0
6
12
experiment
Figure
×
I × ×
70
1. Cable
delay,
18 time
24
0
(hr)
station
marked
with
dots)
for
EURO54
and
CORE3005.
12
experiment
GPS-formatter
70K
6
time
and
18 time
12
experiment
(hr)
difference,
system
6
24
dewar
temperatures
18 time
temperatures (IF1
marked
24
(20K with
0
6
(hr)
12
18
experiment
station
crosses,
marked IF2
time
with
marked
24
(hr)
crosses,
with
dots)
33 31 29 27
3O 28 26 24 22
_14 12 10 8
0
6
12 time (hr)
Figure
2. EURO54
covers
600
ues
below
to
10000
600
ppm
Since there
114
parity parts are
18
errors. per shown
have been
The million
colour
code
(ppm),
val-
in white.
tilting
0
24
problems
6
12 time (hr)
Figure 3:CORE3005 code values
covers
600 to
below
of the recorder
600
heads,
18
24
parity errors.
10000
parts
per
shown
The colour
million
(ppm),
ppm
are
they
had to be sent to Haystack
2000
in white.
IVS
Annual
Report
Onsala
Space Observatory
Observatory
for repair
assembly quality
and
its run
a dry
air kit
Figure as station to be the
clock•
frequency
including
The
in several
selective
availability
2O
I
I
gap
maser
[
been
years. (SA)
[
I
and for
end
I
I
also
drop
system
I
has
Russian
2000
in the
and
with
to the the
head
recording
corresponding Ch1-75
the
next
rms-scatter
in May
(OSO)
installed.
their
Kvarts
the
done
to stabilise
been
and
to problems
in March the
GPS
is due
the
were
In order
GPS-maser
1999
Space Observatory
changes
hours. sensors
offsets
1999
adjusted
Note
no further
temperature the
of February
for the
I
1999
six thousand
in December
has
May
than
values
Since
data
Since
more
humidity
mean
scatter.
of the
necessary
1999.
is now
daily
(rms)
Onsala
in early time
4 shows
mean-square
The
(OSO)
monitoring to the
is used
computer.
adjustment
due
root-
maser
is expected deactivation
of
2000.
I Q)
O3
10 E 0 E l
, ,. • '-2 _o • . . ....._-. _.•'.:....a.-..it-.."-_._.v, .:-=h.=__--'.--._:..-._'." .':-.--- ..-.=. -.: . -. ¢_
-10
".
O
4.
O_ -_an99
_
Figure
4. GPS-rnaser
i
i
I
I
Apr99
Monitoring The
I
Ju199
daily
the
change
monitored
I
of the
vertical
continuously
using
i
i
L
(stars,
,
J
L
Jan00
Oct99
offsets
telescope
L
left scale)
stability of the
an invar
rod
i
I
Apr00
,
local
telescope
L
,
,
J
Jan O_
Oct00
scatter
(dots,
--3--
right
scale).
ties
tower,
measurement
,
Jul00
and root-mean-square
and
position
,
mainly
system
due
[3] (see
to thermal Fig.
expansion,
is
5).
3 E
s
.E
2
O3 e-
c
1
E E
0
cO
O3 C3
-2 1996
Figure
1997
5. Invar
temperature
measurements
in the
2000 IVS Annual
concrete
Report
1998
of vertical
height
wall of the foundation
1999
of the telescope (top curve,
2000
tower right
(bottom
curve
2001
left scale)
and mean
scale).
115
Onsala
Space Observatory
During antennas basis
1999 on top
whenever
vations with 5.
of the
VLBI
rod
telescope
telescope VLBI.
local
tie
system
are
has
GPS
for our
results
measuring
OSO
[4]. The
is available The
at
established
measurements
purposes
also
been
compared
and
to the
by
are
not
Space Observatory
mounting
performed
occupied vertical
(OSO)
two
on a campaign
by astronomical height
GPS
changes
obsermeasured
[5].
Outlook
The RDV
Onsala
and
Space
EUROPE.
A repeated telescope the
For the point
first
outer
Observatory year
measurement
reference
concentrate on
VLBI-GPS
the
invar
Onsala
a new
or geodetic the
(OSO)
on the
network
The
measurement
system repeated
will go on at regular
will
continue
to participate
2001
a total
of 24 experiments
of the are
planned
inner
with
vertical
continuously intervals.
and
footprint
of the
for spring/summer
network
baselines
of the
local
with
baselines
reaching height the
20
observation
series
CORE-3,
is planned.
Onsala
site
2001.
The
and
a classical
footprint
of an approximate
length
survey
of the
measurements
will
of 1 km and
then
70 km.
of the GPS
in the
telescope
observations
tower on
with
top
the
of the
invar
rod
VLBI
measurement
telescope
will
be
References [1] Haas, R. G. Elgered and H.-G. Scherneck, Onsala Space Observatory - IVS Network Station, International VLBI Service for Geodesy and Astrometry 1999 Annual Report, NASA/TP-1999-209243, N. R. Vandenberg (ed.), 90-93, 2000. [2] Bergstrand,
S., R. Haas,
and
G. Elgered,
Geodetic
Very
Long
Baseline
Interferometry
Space Observatory 1999-2000, In: Proc. of the 14th Working Meeting on European and Astrometry, P. Tomasi, F. Mantovani and M.-A. Perez-Torres (eds.), 105-106, [3] Elgered, G., and R. Haas, Geodetic Very-Long-Baseline 1997 1998, In: Proc. of the 13th Working Meeting W. Schliiter and H. Hase (eds.), 60 64, 1999. [4] Bergstrand, S., R. Haas, and J. M. Johansson, In: IVS 2000 General Meeting Proceedings, 2000-209893, 128-132, 2000.
VLBI 2000.
at the
In:
Onsala
for Geodesy
Interferometry at the Onsala Space Observatory on European VLBI for Geodesy and Astrometry,
A new GPS-VLBI N. R. Vandenberg
tie at the Onsala and K. D. Baver
Space Observatory, (eds.), NASA/CP-
[5] Bergstrand, S., R. Haas, and J. M. Johansson, An independent stability check of the Onsala 20m radio telescope using the Global Positioning System, In: Proc. of the 14th Working Meeting on European VLBI for Geodesy and Astrometry, P. Tomasi, F. Mantovani and M.-A. Perez-Torres (eds.), 83-88, 2000.
116
2000 IVS Annual
Report
t_
f_M
565705 Shanghai
Astronomical
Observatory,
Chinese
Academy
Seshan Xiaoyu
Hong,
VLBI
Shiguang
Seshan
of Sciences
Station
Liang,
Xinyong
VLBI
Station
Report Huang,
Wenren
Wei
Abstract The following reports observations made during
1.
the status of the Seshan the reporting period and
VLBI station, its future plans.
including
its
facilities,
personnel,
Introduction The Seshan
25 meter
radio
telescope
is an alt-az
antenna
run by Shanghai
Astronomical
Obser-
vatory (SHAO), Chinese Academy of Sciences (CAS). The telescope is located about 30 km west of Shanghai. It is one of the five main astronomical facilities of Chinese National Astronomical Observatories. The VLBI station is a member of the EVN, APT and IVS. 2. 2.1.
Facilities Receivers
Five receivers
bands of VLBI observations are listed in Table 1. Table Band
Bandwidth
are
1. VLBI
available
Receivers
at Seshan
of Seshan
Efficiency
Station.
The
parameters
Satation
Type
System
temperature
(cm)
(MHz)
(%)
18
1620-1680
40
Room
13
2150-2350
45
Room
6 3.6
4700-5100 8200-9000
58 48
Cryogenic Cryogenic
45-50 _ 50
1.3
22100-22600
_20
Cryogenic
_110
The Seshan observations.
station
is equipped
with
of the
(K)
S/X
Temperature
_ 100
Temperature
_ 100
dual
band
receivers
for astrometric
and
geodetic
The X-band system has been upgraded to the wideband system, from 8200 MHz to 9000 MHz, successfully last year. We will join wideband experiments this year. The test experiment C3006 has been done on Dec. 13, 2000. The correlated results showed good showed the large increase in SEFD's from low to high frequency. 2.2.
Recording
quality of data. The results also The situation will be improved.
System
VLBA, MK4 (VLBA4), and $2 recording systems Upgrade of Seshan MKIV recording system had been
are available now at Seshsan VLBI station. done successfully in the end of Aug. 2000.
MKIV upgrade of Seshan station has been carried out with the great help of Team China # 2 in April, 2000. Team China # 2 was composed of six experts from Europe and US. They are Dr.
2000
IVS Annual
Report
117
Seshan VLBI Station
Shanghai Astronomical Observatory, Chinese Academy of Sciences
Ralph Spencer, Dr. Dr. Ed Himwich. The first fringe
Les Parry,
Dr.
test experiment
to find good fringes, because of problems
Michael
Wunderlich,
was done on Apr.
were found
Gino
several tracks were dead, and the parity errors with the fiat cables of the read/write modules,
also on FT003
and
C00C3
Tucarri,
14 with VLBA4
soldering. The problems were solved later on. Fringes were found in the second fringe test with Fringes
Dr.
VLBA
experiments
and later.
Dr.
Chopo
Ma, and
rack and recorder.
It failed
of several tracks bad connectors, MK4
were very high capacitors and
formatters
Seshan
MKIV
on Aug.
27.
participated
in
experiments of EVN, NASA, VSOP, APSG etc. since the end of Aug. 2000. Many thanks EVN, NASA, Team China #2, Dan Smythe, and all people who worked on our upgrade. 3.
Personnel
There are some changes of the staff in Seshan Station are listed in Table 2. Table Name
2 - The
Hong
main staff in Seshan
VLBI
at Seshan
email
address
and
Chief Scientist
[email protected]
Shi-guang Liang Zhiban Qian
Research Research
Professor Professor
and
Chief Engineer
[email protected] [email protected]
Xinyong
Senior
Engineer
[email protected]
Senior
Engineer
[email protected]
Senior
Engineer
[email protected]
Jiazheng He Qing-yuan Fan
Senior Senior
Engineer Engineer
[email protected] [email protected]
Song-lin
Engineer
Huang Wei Xue
Chen
[email protected]
Xiu-ling Chen Engineer The email a(:counts for the station
Geodetic
Observations
13 geodetic
experiments
The experiments
Future
have
are listed
VLBI
Station
Professor
Zhuhe
5.
The main staff members
Research
Wenren
2000.
station.
Position
Xiaoyu
4.
to JIVE,
are:
[email protected] [email protected];
[email protected].
been run by the Seshan in Table
Station
from March
1999 to the end of
3.
Plans
The improvement of quickly switching frequencies of Seshan station will be implemented this year. After that, it will be easy to switch between S/X band and L- or C- or K-bands. The Geodetic VLBI observation plan of Seshan VLBI station for 2001 is listed in Table 4.
118
in
2000 IVS Annual Report
Shanghai Astronomical
Table
3 List of Geodetic
VLBI
observations
DATE 07-APR 21-APR 26-JUL 28-JUL
1999 1999
Mar.
HOUR
CORE-B502 CORE-B503
24.0 24.0
CRF-08 CORE-B504
25.0 24.0
APSG05 APSG06
11.0 25.0
04-NOV 29-DEC
1999 1999
CORE-B505 CORE-B506
24.0 24.0
CORE-B801 CORE-1004
24.0 06.0
2000 2000
02-OCT 02-NOV
2000 2000
APSG7 CORE-B802
24.0 24.0
14-NOV
2000
CORE-3006
06.0
observation
1999 to Dec.
EXPERIMENT
1999 1999
4 The Geodetic
2000 IVS Annual Report
1999 1999
From
01-NOV 03-NOV
12-JAN 26-SEP
Table
Seshan VLBI Station
Observatory, Chinese Academy of Sciences
plan of Seshan
VLBI
DATE
EXPERIMENT
HOUR
05-Feb 2001 05-Mar 2001 26-Mar 2001
CORE-1009 CORE-1010 CONT-M3
24.0 24.0 24.0
27-Mar 28-Mar
2001 2001
CONT-M4 CONT-M5
24.0 24.0
16-Apt
2001
CORE-1011
24.0
14-May 2001 25-Jun 2001 09-Jul 2001
CORE-1012 CORE-1013 CORE-1014
24.0 24.0 24.0
20-Aug 2001 10-Sep 2001 22-Oct 2001
CORE-1015 CORE-1016 CORE-1017
24.0 24.0 24.0
05-Nov 12-Nov
2001 2001
CORE-1018 APSG-8
24.0 24.0
19-Nov
2001
APSG-9
24.0
03-Dec
2001
CORE-1019
24.0
station
2000
for 2001
119
zoo Simeiz Station
U//z SSS-7o
Laboratory of Radio Astronomy of Crimean Astrophysical Observatory
Simeiz
Station:
Geodetical Experiments Observations N. Nesterov,
A.
and
Single
Dish
Volvach
Abstract This report summarizes an overview of the VLBI activities during 5 years. Horizontal station velocity was determined and estimates of its accuracy were obtained. An overview about the single dish activity and of the stability of the station with respect to local marks is given also. 1.
Observations
1.1.
and
Data
Analysis
IVS
All available dual-band geodetic 2000.72 were used in the analysis: sessions with measurements
MARK III VLBI observations for 21 years, from 1979.59 till 3058 sessions, 3005651 observations including 36 successful
participation of the station Simeiz for 6 years: of group delays (Petrov et al., 2000).
1994.48-2000.36
with
19 631 good
Simeiz station moves with respect to the Eurasian tectonic plate considered as rigid with rate 2.8 + 0.9 mm/year in the direction with azimuth 27 dog. Thorough investigation of possible systematic effects has been done and the reliability of the estimate of the uncertainty has been evaluated. Performance of the receivers and H-maser was examined. The stability of the station with respect to local marks was investigated and an enhancement of inclination of the azimuthal axis (Pisa effect) of the telescope with velocity 2(_6 per year was disclosed (see Fig.l). The following position of the station Simeiz at the epoch 1997.0 and its rate of change ITRF97 system were obtained:
X = 3D3785231.070
± 0.006
m
-_ -- 3D6.8
Y -- 3D2551207.415
± 0.004
m
1_ -- 3D5.0 • 10 -l° ± 0.4 • 10 -l°
m/see
Z -- 3D4439796.360
± 0.008
m
Z -- 3D2.1 • 10 -10 ± 0.8 • 10 -l°
m/sec
The details 1.2.
Single
of the analysis
are stated
in paper
• 10 -10
of Petrov
+
0.3 • 10 -1° m/sec
et al., 2000.
Dish
The antenna
temperatures
from ten sources
were measured
by the standard
ON
Before measuring the intensity, we determined the source instrumental position radio telescope was then pointed alternately on the source and on the distance off source.
The
antenna
temperature
from a source
was defined
as the
signal
intensity
under study were calibrated Vir-A, whose flux densities Table
1 shows measured
and
estimated
the rms error
using measurements are given in Mark-IV flux densities
of the
mean.
between
of sources
The fluxes
at 8 GHz as follows:
the
Depending on the and then calculated from the objects
of the calibration sources Cyg-A, Cas-A, Field System Documentation (1993).
designation, column (2) and column (3) - date and time of observations, column (5) - the rms errors of the measured flux densities.
120
OFF method.
by scanning. The of 5 beamwidths
difference
radiometer responses averaged during 10 s at two different antenna positions. intensity of the emission from sources, we made a series of 20-60 measurements the mean
in the
column column
Tau-A,
(1) - IAU source (4) - flux densities,
2000 IVS Annual Report
Laboratory
of Radio
Astronomy
of Crimean
I
Astrophysical
I
Observatory
I
Simeiz
I
I
Station
I l-
100
i) 5O
0
,
,
,
,
I
,
,
,
1970
Figure
1.
seconds)
Deviation at different
of
azimuthal
0316+413 0528+134
,
,
I
,
,
,
,
1980
axis
of the
I
,
,
,
,
1985
radiotelescope
I
,
,
,
,
1990
with
respect
I
,
,
1995
to
the
1. Single DAT(YY.MM)
dish
8 GHz
measured
TM(DD.UT)
flux
local
,
,
I
2000
plumb
line
(in
arc
densities.
FLUX(Jy)
SIGM(Jy)
97.09
4.931
22.4
97.12
10.668
20,9
1.1 1.4
97.09
5,149
3.3
0.7
98.02
1,685
3.1
0.9
97.09
4,999
5.2
0.5
0642+449
97.09
30.294
1.9
0,3
98.02
1.622
3.3
0,9
98.04
20.303
0.8
98.06 97.08
23.474 29.651
2.7 2.5 30.5
0.5 3.7
97.08
29.668
22.3
1.4
97.09
4,898
19.2
1.6
97.12
10.661
21.2
0.7
2037+421
Report
,
0552+398
1226+023 1253-055
Annual
,
epochs.
SOURCE
IVS
I
1975
Table
2000
,
98.02
2.344
20.9
1.0
2145+067
98.02
2,355
6.2
1.3
2200+420
98.02
3,406
1.3
2251+158
98.02
3.417
3.8 11.2
1.7
121
Simeiz
2.
Station
Laboratory
Discussion Estimates
of Results of the horizontal
VLBI observations of 3 million VLBI respect
and
of Radio
velocity
direction. Thorough the estimate of the
tectonic
of Crimean
Astrophysical
Observatory
Conclusions of the radioastronomical
carried out under geodynamics observations has been analyzed
to the Eurasian
Astronomy
plate considered
station
Simeiz were obtained
using
programs during 1994-2000. The complete set and it was found that the station moves with as rigid with rate 2.8 + 0.9 mm/yr
study of possible local systematic uncertainty has been evaluated.
in a north-east
effects has been done and the reliability The stability of the station with respect
of to
local marks was investigated and an inclination of the azimuthal axis (Pisa effect) of the telescope with velocity 2_.t6per year was disclosed. The estimate of vertical motion of the station 2.6 4- 3.0 mm/yr is not statistically significant. The results of single dish S/X observations then reviewed
after
experiment
of sources
to check the consistency
used for geodesy of data
investigations
can be
from each source.
46 °
44 °
42 °
North
40 °
Anatolian
fault']
28 °
32 ° Figure
2.
Motion
36 ° of the
station
40 °
Simeiz.
References [1]
L. Petrov,
[2] Mark Space
122
IV
O. Field
Flight
Volvach, System,
N.
Nesterov
Version
//Astron. 8.2,
September
Let.
2000.-submitted.
1,-1993,-
Space
Geodesy
Program.
NASA/Goddard
Center.
2000
IVS
Annual
Report
-
,. -/i_>
"
,l/
555707 Institute
of Applied
Astronomy
of Russian
Svetloe Sergey
Academy
Radio
Svetloe
of Sciences
Astronomical
Smolentsey,
Dmitriy
Station
Observatory
Ivanov,
Zinovy
Malkin
Abstract This in the
1.
report period
provides after
information
the last
about
changes
in the
Svetloe
Radio
Astronomy
Observatory
status
of Applied
Astronomy
IVS report.
Introduction Svetloe
(IAA) project
Radio
Astronomical
Observatory
was founded
by the Institute
as the first station of Russian VLBI network QUASAR. Sponsoring organization of this is the Russian Academy of Sciences (RAS). The site is located at the Karelian Neck near
Svetloe village in about 100 km towards North from St. Petersburg. observatory are 32-m radio telescope RTF-32 and technical systems observations.
In addition,
a permanent
GPS
receiver
was installed
at Svetloe
During last two years Svetloe observatory regularly participated programs including VLBI and RL VLBI observations of quasars, recording terminal S2-RT. Svetloe observatory participated REF permanent station.
in several
2.
equipment
Radio The
telescope results
and
VLBI
of measurements
regional
of radiotelescope
Table 1. Parameters Wave band, 3.5
ofthe
cm
and global
parameters
radio telescope
in 1996.
in various radio astronomy Sun, planets, asteroids using geodetic
(for LRP)
SEFD 430
6 13
The basic instruments of the provided realization of VLBI
projects
are presented
"Taifun"
Enterprise,
Obninsk,
Russia,
and provides
in Table
1.
Tsys, K 58
180 30O
relative humidity, wind 3D velocity and direction. Figures 1 4 show a common view of Svetloe
is a EU-
RTF-32.
32 43
Field System is now fully involved in observation, registration, and investigation rections for radio telescope deformations are determined and used for pointing. A new automatic meteo station was installed at Svetloe in 2000. It has been by the
and
measurement
observatory,
RTF-32
process.
manufactured
of temperature, radio
Cor-
antenna
pressure, and
other
equipment.
2000
IVS
Annual
Report
123
Svetloe Station
Institute
Figure
124
1. Radio
of Applied
telescope
Astronomy
of Russian
Academy
of Sciences
RTF-32.
2000
IVS Annual
Report
Institute
of Applied
Astronomy
Figure
of Russian
2. Svetloe
Academy
station:
of Sciences
laboratory
building
Svetloe Station
and
radiotelescope
RTF-32.
t
Figure
3. R:TF-32
GPS/GLONASS 2000 IVS Annual
antenna, receivers
Report
Trimble during
GPS IGEX
and Javad (:ampaign.
Figure
4.
Radio
receivers
for 3.5 and
13 cm wave
bands. 125
Svetloe
3.
Station
Institute
Geodetic
Survey
at
Svetloe
of Applied
Astronomy
of Russian
Academy
of Sciences
Observatory
Local geodetic
network
at the Svetloe
ob-
servatory includes 9 reference points (see Figure 5): 102, 107, 108, 1(19 are ground marks (the latter connected with a pad for mobile systems), 101, 103, 104 are located at the roof of two story laboratory building and designed for installation of GPS/GLONASS geodetic units,
receivers or conventional 110 is the intersection of
radiotelescope RTF-32 axis, and 106 is intermediate mark on its foundation. GPS receiver installed SVTL).
104 103 101
Trimble 4000SST is permanently on the 101 mark (12350M001,
Since the last report several new measurements were made at the network and mu-
106 110
tual eccentricity between marks rived fl'om common adjustments
109
were deof GPS
and conventional surveys made in 19931999. Accuracy of the local geodetic network is about 2 mm and intersection of
108
50 m
radio telescope axis is tied to the network with accuracy about 5 ram.
Figure 5. Local geodetic network at Svetloe.
.
Outlook We plan for the near future: • Begin experimental VLBI observations on Svetloe-Zelenchukskaya Zelenchukskaya located in North Caucasus is the second station
126
• Install
the first two channels
of the new DAS developed
• Install
a new radio
control
telescope
baseline (IAA observatory of the QUASAR network).
at the IAA.
system.
2000
IVS
Annual
Report
i .:-....._
;,
t]
.............
Figure
and
occasionally.
_4
IVS Annual
HartRAO,
(IRIS-S):
• Measurement of Vertical Crustal Motion in Europe by VLBI (EUROPE) 6 sessions in 1999 and 7 sessions in 2000 with the stations Nyltlesund, Onsala, per year,
year
Surveying
Hobart,
Simeiz,
per
Interferometric
Fairbanks,
O'Higgins
2000
Bonn
Activities
Bonn, Nussallee 17, D-53115 Bonn, Operation Center were concentrated serving
IVS
1. European
ll'Malera_
;:=
'.
VLBI
i L-;2:2
'_
"
'
network
157
Operation
Center
• Continuous
at the
Geodetic
Observations
with stations HartRAO, Antarctic station Syowa The sessions
Institute
Bonn
of the O'Higgins,
Geod_tisches
Rotation Fortaleza,
of the Hobart,
Earth
Institut
der
Universit_t
Bonn
(CORE-OHIG):
Kokee and
DSS45 plus the
Japanese
operational tasks mainly consisted of preparing the detailed observing schedules for all listed above. The schedu]es were prepared with the SKED software on HP-UX platforms.
The work also involved sending of tapes, communication with stations, fault analysis, and arrangements for special sessions and testing schemes. Arno Mfiskens takes care of the IRIS-S and the CORE-OHIG sessions while Axel Nothnagel is responsible for the EUROPE project.
158
2000
IVS
Annual
Report
Zoo ZooW'25
/
NASA
Goddard
Space
Flight
5557/I
CORE
Center
CORE
Operation Cynthia
Center
Operation
Center
Report
C. Thomas Abstract
This
report
December the
1.
evolution
CORE The
gives
2000.
The
of the
Program
continuous
a synopsis report different
of the
forecasts CORE
activities
of the
activities
plaamed
CORE
Operating
for the
year
Center 2001.
from
The
March
outlook
1999
to
summarizes
programs,
Description observations
of the
rotation
of the
Earth
(CORE)
program
was initiated
the geodetic very long baseline interferometry (VLBI) community in 1997. The program carried out using geodetic VLBI stations for data acquisition and VLBI analysis centers processing and analysis. The CORE program will evolve over the period 1997-2003. The goal of the CORE program is to generate a continuous high accuracy Earth set for Earth science and global change research. The program data for studies of the continuous momentum exchange among
availability
of continuous, that became
high accuracy available
Earth
during
rotation
the third quarter
rotation
have been impossible. Mark III experiments
attain precision of at least 3.5 #s for UT1 and 100 #as in pole position. has the potential for a typical precision of 2-2.5 #s in UT1 and 30-40/,as sessions with a 6-station network. The
is being for data data
will produce basic observational the solid Earth, the atmosphere,
and the hydrosphere, enabling exciting research areas that heretofore The current Earth orientation parameter goal of the pre-CORE
Mark IV technology
by
data
The full CORE in pole position, will be possible
is to
program for daily due to the
of 2000. The Mark IV correlator
became as efficient as the Mark III correlator during the last quarter of 2000. Improved sensitivity of the Mark IV data acquisition system together with the high playback efficiency of the Mark IV correlator are both necessary to produce the expected results for CORE. CORE sessions were run with five basic network configurations: CORE-A, CORE-B1, COREB2, and CORE-B3 during 1997 and 1998. During 1999, the networks of the CORE-B changed and the sessions were named CORE-B4, CORE-B5, and CORE-B6. The CORE-A were simultaneous
with NEOS
sessions
and
CORE-B
and NEOS
sessions
sessions sessions
were on sequential
days
during both 1998 and 1999. During 2000, the CORE-3 sessions started in July and were performed in Mark IV mode. It was decided that the CORE-A/NEOS series of 76 sessions was sufficient for the analysis of EOP estimated from different networks and it was therefore ended. process of filling in the observing week that will eventually be continuous in CORE, network was moved from Tuesdays to Mondays and renamed CORE-1.
2.
CORE
Sessions
This section
During
displays
It also lists other
programs
the purpose
IVS
Annual
Report
1999
to
December
of the CORE-A,
2000
CORE-B,
CORE-1
and CORE-3
sessions.
used by CORE.
• CORE-A/CORE-l: These continuously using different
2000
April
To start the the CORE-A
experiments networks.
validated
the
CORE
concept
of measuring
EOP
159
CORE Operation Center
NASA Goddard Space Flight Center
The network for CORE-A included Fairbanks, HartRAO, Westford during 1998. During 1999 the network consisted
Hobart, of three
banks, HartRAO, Tsukuba, Matera,
consisted
In 2000, the
and Algonquin. and Hobart.
CORE-As
The other
were scheduled
once
three
stations
per month
until
Algonquin, Matera and constant stations: Fair-
July.
of Medieina,
Westford,
In July,
CORE-As
the
were moved to Mondays and renamed CORE-1 because Algonquin was added to the NEOS weekly sessions. The network for the CORE-A and CORE-1 was Algonquin, Fairbanks, HartRAO, Matera, Tsukuba, and Hobart. • CORE-B: The purpose of these sessions is to provide additional data for comparison of EOP measurements, to obtain long 48-hour data sets for geophysical studies and to provide observing ability
sessions
to participate
• CORE-3: series
during
These
in future
sessions
was named
which
for the
started third
the stations regular
CORE
can demonstrate
in July of 2000 and
is data
from other
programs
established
3.
Current
Analysis
Comparisons there are biases
were observed
monthly.
week since it is scheduled
following the NEOS sessions. The CORE-3 sessions CORE sessions, recorded in a Mark IV mode. There
performance
and
their
sessions.
day of the work
ROPE), USNO (NEOS, NAVEX, CRF), Some of the data is used to help determine
their
The
were the first of the regular,
by Bonn
(IRIS-S,
CORE-3
for Wednesdays
CORE-OHIGGINS,
operational
and
EU-
and GSI (APSG) that are used by the CORE program. the direction of the CORE program during its evolution.
of CORE
of daily EOP estimates made by the CORE-A and NEOS networks show that at the level of about 50 gas in polar motion and 2 #s in UT1 between simultaneous
CORE-A and NEOS measurements. The wrms differences are 232 I*as, 165 #as, 9.8 Its between X, Y, and UT1 estimates, respectively. The source of these differences is most likely unmodeled or mismodeled site motion, which we are currently investigating. One of the measures of performance of the CORE experiments
is the size of the formal
EOP
uncertainties. The uncertainties range from about 70-100 #as for X-pole, 50-100 #as for Y-pole, and 2.5-3.5 #s for UT1. Based on the observed differences between simultaneous CORE-A and NEOS sessions, the formal EOP precisions should be multiplied by about a factor of 1.5. The observed UT1.
uncertainties
4.
CORE
The
are generally
Evolution
the minimal
goal of 100 ILas for PM and 3.5 its for
Family
Table 1 lists the key technical report will know who to contact 5.
less than
personnel and their responsibilities about their particular question.
so that
everyone
reading
this
of CORE
As of the end of 2000, the CORE
observing
program
for 2001 and tile Mark
IV correlator
plans
were proceeding. • The CORE-1 160
sessions
have been scheduled
monthly
and will be observed
in a Mark IV mode. 2000 IVS Annual Report
NASA Goddard Space Flight Center
CORE Operation Center
• The CORE-3 sessions have been scheduled bi-weekly during the year. CORE-3 network will begin bi-weekly starting July of 2001. • The correlator
has been
operating
as efficiently
as the Mark
Responsibility
Tom Buretta
Recorder
Brian
Analysis
Corey
Center Agency
and electronics
maintenance
Haystack Haystack
Irv Deigel Frank Gomez
Maser maintenance Software engineer
David
Gordon
Analysis
Ed Himwich Chuck Kodak
Network Receiver
Cindy
Lonigro
Analysis
Raytheon/STX
MacMillan
Analysis
NVI, Inc./GSFC
Dan
Leonid
Petrov
Analysis
David
Shaffer
Sources
Dan Smythe Cynthia Thomas
Nancy William
The
tentative
Start
Date
Coordinator maintenance
for CORE
stations
NVI, Inc./GSFC HTSI
NVI, Inc./GSFC and antenna
parameter
prepare CORE schedules
experiments
Organizer
CORE
CORE
Table 2. Planned
Raytheon/STX
manager Procurement operations
Wildes
HTSI Raytheon/STX
for the Web site
Tape recorder maintenance Coordinate master observing
Vandenberg
evolution
of
maintenance schedule
Haystack NVI, Inc./GSFC
and
necessary
and
sked
for CORE
plan for the next few years
NVI, Inc./GSFC GSFC/NASA
is summarized
in Table
Name
Avg Days per Week
CORE-A
monthly
2.0
Mark IV Correlator < Mark III Correlator
l-Jul-2000
CORE-3
monthly
2.0
Discontinued
1-Jan-2001
CORE-1
monthly
2.4
l-Jan-2001 l-May-2001
CORE-3 CORE-C
bi-weekly 8 sessions
2.4 2.5
l-Jul-2001
CORE-3
weekly
2.8
We are working
IVS
Annum
2.
Notes
l-Feb-2000
2000
Inc.
observing
program
of materials
Radiometrics/NVI,
CORE Evolution
Experiment
need more antenna
a second
III Correlator.
Table 1. Key Technical Staff of the CORE Operations Name
In addition,
on identifying observing
Report
the participating
to fulfill this plan.
two different
stations
CORE-A
CORE-3
for each new CORE
The goal for CORE
efficiency
is continuous
networks
network. observing
We will but we
161
CORE Operation Center
recognize
that
NASA Goddard Space Flight Center
it will be very difficult
observing is costly both in funding ideas you have about how to attack welcome! 6.
CORE
Review
A panel,
co-sponsored
to fill in the weekend
days for CORE-5,
-6, and -7. Weekend
and in inconvenience to operators. We would appreciate any this problem. Volunteers for weekend observing would be very
Panel by NASA
and IVS, met in early
2001 to review
make recommendations about the best way VLBI can contribute report of the panel will be input to the master schedule planning
the CORE
program
to space geodesy programs. for 2002 observing.
and The
References [1] Clark, T.: CORE White Paper,
162
June 2, 1997
2000 IVS Annual Report
U.S.
Naval
NEOS
Observatory
U.S.
Naval
Observatory Kerry
Operation
Kingham,
M.S.
Operation
Center
at USNO
Center
Carter
Abstract This
1.
VLBI
VLBI
covers
the
activities
of the NEOS
Operation
Center
at USNO
for 1999
and
2000.
Operations
NEOS session, duration
report
operations
in the period
on Tuesday-Wednesday "intensives" for UT1 stations
at Gilmore
covered
consisted
of one 24-hour
duration
NEOS-A
observing
of each week, for Earth Orientation, together with daily one-hour determination. The operational NEOS-A network has included
Creek
(Alaska),
Kokee
Park
(Hawaii),
Wettzell
(Germany),
Fortaleza
(Brazil), Ny-Alesund (Norway), Algonquin Park (Canada), Westford (Massachusetts), Matera (Italy), Yellowknife (Canada) and Green Bank (West Virginia). No more than six stations were used in any given NEOS-A. During the reporting period, the Green Bank station was closed The daily intensive sessions switched from the Green Bank - Wettzell - Wettzell network. All sessions
are correlated
at the Washington
Correlator,
which
and is no longer available. network to the Kokee Park
is located
at USNO
and
is run
by NEOS. 2.
Staff
Changes
During the reporting period, T.M. Eubanks left USNO to pursue opportunities in the private sector. B.A. Archinal left USNO for a job at the U.S. Geological Survey in Flagstaff, AZ. M.S. Carter
2000
has assumed
IVS Annual
Report
the scheduling
duties.
163
CRL Analysis
+J
Kashima
Center
Analysis
Center
at
Space Research
Center,
Communications Ryuichi
Communications
Research
Research
Laboratory
Laboratory
Ichikawa
Abstract The aim of the Key Stone Project is to obtain precise relative positions of four stations using VLBI, SLR, and GPS on a daily basis by the Communications Research Laboratory. VLBI results spanning the last three and half years indicate that the Miura and Tateyama KSP sites are moving NNW with respect to Kashima at velocities of 17.0 and 20.9 ram/year, respectively. For two months after June 2000, the baseline length between Kashima and Tateyama was shortened by about 5 cm caused by a dike intrusion and co-seismic offsets between the Izu islands. We also carried out research and development such as evaluations of tropospheric path delay and ionospheric electron content, monitoring of fluxdensity variations of radio sources using the KSP network. This report summarizes the results from these research fields using the KSP network of CRL to the end of 2000.
1.
Introduction The
KSP
cations the
has
KSP
of the
Kanto
Analysis Crustal
is not
only
strain
aimed
development
a minimum automated
compared.
at
We describe
Japan
by
One
of the
main
plate
crustal
geodesy.
VLBI
site,
analysis
the
results
Communi-
objectives
deformation
to provide
frequent
the
boundary
It is designed
and
at each
some
at the
monitoring
allows
together
area,
GPS.
accumulation
operations
design close
and
of space
of human
techniques
be
and
metropolitan
SLR,
but
to make
analyzed
the
as fast
By placing
and
using
also
frequent
results
experiments. different
of
region
independently
KSP
network
in
la plots
VLBI.
based
oil the
scattering
at three Miura
20.9
mm/year
Tateyama
toward
Sagami
Trough.
Figures
la and
5 cm
2000, in two
observed
the
months.
the effect
2a show
namely
and
Network
the
of the
their
formal
horizontal
NNW,
and
moving
respectively.
extraordinary
Accumulated
length
The
velocities the
with
displacement
and
Tateyama
quality after
which
stations are
September
and
to
Kashima moving
Sea plate VLBI
Kashima at KSP
per half
evident
30,
and
GPS
Tateyama
toward
and
1997
are
NNW northern
and 1997
indicate
that
of
17.0
and
at Miura
and
Honshu
measurements
after
is shortened
north-east
VLBI
January
velocities
toward
beneath
using
from
years at
and sites
year)
to Kashima
three
velocities
in both
between
results
relative
last
Philippine
drifts
data
(millimeters
respect
The
Kashima
experiment.
Tateyama)
span
of the subducting
baseline
errors.
site
Miura, are
between in VLBI
of each
measurements sites
baseline
improvements
duration
(Koganei,
VLBI
Tateyama
suggest
gradual
extended
sites
These
and
of plots the
KSP
2000.
the
KSP
lengths
shows
the
lb shows
June
the
estimated
figure
reflecting
Figure
of June
the
This
remarkable, GPS
using
deformation
Figure
210
KSP
Tokyo
VLBI,
deformation
its
Results
using
the
can
the
using
report.
2.1.
to
with
above-mentioned results
around
technical
In particular,
three
obtained
2.
The and
possible
as possible.
out (CRL),
regional
district.
for research
observations
this
carried
Laboratory
is to monitor
utilized
the
been
Research
are
along the
end
by about presented
2000 IVS Annual
in
Report
Kashima Space Research Center, Communications Research Laboratory
figure 2b. GEONET
Similar displacement at four GPS sites by Geographical Survey Institute (GSI)
...............
,
CRL Analysis Center
(Katsuura, Kyonan, Miura, and are also shown in the figure.
Tateyama)
of
......
139
140
PH
141
km 0
50
139
100
140
141
Figure 1. (a) Estimated baseline length between Kashima and Tateyama using VLBI. The formal error of each estimation is shown by a vertical bar in both figures. The variations in baseline length are fitted by linear lines and the best fit line is shown by straight solid lines. (b) Observed horizontal site velocities (centimeter per year) relative to Kashima site. The velocities from VLBI and KSP GPS from January 1997 to June 2000 are shown.
Following
the magma
26 and 27, 2000, crater the islands, Miyakejima. continued inversion
intrusion
in the hu
Islands
(about
subsidence and volcanic eruptions In addition, high seismic activity
around Miyakejima and Niijima-Kodushima using half-infinite elastic model, the crustal
150 km south
since the end of June. deformation at Tateyama,
km north-east of Kodushima island, is caused by a dike intrusion seismic offsets between the islands [1]. The strike of the simulated perpendicular to the azimuth from Kodushima toward Tateyama. can move the Tateyama 2.2.
Evaluation
site toward
of tropospheric
the north-east path
of Tokyo),
during
June
continued in July and August at one of and significant crustal deformation has According to the located about 100
at about 3 km depth and codike is N140E, which is almost This geometrical configuration
by the deformation
due to the simulated
dike.
delay
The repeatability of the baseline length of KSP VLBI measurements tends to be degraded in summertime. A correlation analysis between measured baseline lengths and surface temperature data was made, and it suggested that an apparent position change of the Kashima site occurred [2]. In June 1998, we initiated a field experiment for detecting and characterizing water vapor variations using water vapor radiometers (WVRs) at KSP Kashima site and Tsukuba. A WVR at Tsukuba is deployed by the Meteorological Research Institute (MRI) of the Japan Meteorological Agency
(JMA).
and Kashima
Time
series of atmospheric
gradients
estimated
by WVR
slant
delays
at Tsukuba
are compared.
2000 IVS Annual Report
211
CRL
Analysis
Center
Kashima
Space
Research
Center,
Communications
139
Research
140
Laboratory
141
1oo KSP KSP
VLBI VLBI
*
GSI
GPS
[after
Kashima-
6/26t2000]
a
Tateyama
_p
•
2
2FT
_
._
-
50 "
Kllhi
_,
_odujin_ 5/31/2000
7/1/2000
811/2000
9/t/2000
(FIX)
Tateyama
.is,_ _
10/2/2000
ma
Miyakejima
NA
_
VLBl(Icm}
_
(;|_J(;_;l(IL'm)
TIME PH km 0
50
100
33
Figure KSP
2.
(a)
Estimated
network.
GPS
Accumulated
In spite
baseline
results
displacements
from
of relatively
short
nlospheric gradients solutions weather pattern caused large numerical 2.3.
weather
Evaluation Ionospheric
length
of the
prediction
between
GEONET VLBI,
KSP
distance
Kashima
and
Geographical
GPS
and
between
Tateyama
Survey
GEONET
GPS
Tsukuba
and
using
Institute sites
VLBI
(GSI) from
Kashima
models
correction
in order
to investigate
electron
content
with
GPS-based
measurement is useful for single band tic VLBI with a single band receiver.
Earth
these
results
ionosphere
total
and
are
July
GPS
also
of
shown.
54 km)
the (b)
to September
(about
are significantly different. This result suggests differences. We are now analyzing the output
of ionospheric delay
by
33
2000.
the
at-
that the mesoscale of high resolution
more deeply.
electron
content
(TEC)
VLBI application; for example, pulsar astrometry and geodeTo investigate the accuracy of GPS-based ionospheric TEC
measurement, three cases of TEC estimation methods were compared with those from dual band VLBI observations of the Kashima-Koganei baseline [3]. The comparison study indicated the GPSbased TEC measurement can correct ionospheric delay in VLBI observations in almost the same accuracy
with S/X dual band
VLBI
observation.
This result
is encouraging
to apply
GPS derived
TEC to single band astrometric VLBI observation. Also realizing single band geodetic VLBI benefit at lower cost single band receiver instead of dual band receiver and more data channels can be used for X band 2.4.
Monitoring Compact
and
signal. flux strong
density radio
variations
sources
of radio
are repeatedly
sources
observed
in regular
geodetic
VLBI
exper-
iments under the KSP [4]. The two main purposes of the KSP VLBI network are to precisely measure relative site positions and to monitor their variations with a minimum delay of processing time.
212
For these
purposes,
time
delays
between
signals
received
at two sites
and
2000
their
IVS Annual
rates
of
Report
Kashima
Space
Research
Center,
Communications
Research
Laboratory
CRL
AnMysis
Center
change axe obtained through data correlation and bandwidth synthesis processing performed in real-time. The five years of the observed data show irregular variations in the flux densities were detected for several radio sources using the source 2134+004 as the calibrator. 3.
Staff The
staff members
• Kondo
4.
Tetsuro,
• Koyama
Yasuhiro,
• Ichikawa
Ryuichi,
• Amagai
Jun,
Current
Status
who are contributing Responsible
for overall
Development Research
Maintenance and
to KSP
of data
Future
operations
of data
for crustal
Analysis
at the CRL are listed
below:
and performance.
analysis
software.
deformation
analysis
Center
and atmospheric
modeling.
system.
Plans
As of mid-September 2000, the crustal deformation around Izu islands almost decayed according to the results from continuous GPS measurements of GEONET at the Izu islands by GSI. However, it is very important to monitor a postseismic stage in order to understand the recent event around the islands. Thus, we made a decision to continue
the tectonic process of the KSP observations
at least for one year regularly though we had a plan to close the KSP in spring 2001. At present, the atmospheric gradient models [5][6] are not used in the operational the KSP VLBI. We are now modifying the VLBI analysis software position determination using atmospheric gradient model. The web server
for the Analysis
Center
is provided
by CRL.
to improve The URL
analysis
the accuracy
address
of
of the
is
http://ksp.crl.go.jp/index.html The KSP web site holds all the data obtained by the KSP VLBI network. Baseline lengths, site positions, flux densities of observed radio sources, estimated earth orientation parameters are available on our web site. Our analysis results of the site positions have been generated using SINEX format. References [1] Kimata, F, Okuda, T, Yamaoka, K, Fujii, N, Kato, T, Nakno, S, Sakai, S, Reddy, C D, Tabei, T, and Eguchi, Y, Crustal deformations observed in the volcano-swarm activity in the Izu Islands, central Japan using GPS, The 2000 AGU Fall Meeting, 2000. [2] Kondo et al., Atmospheric Gradient Effects on the Metropolitan Area, in preparation, 2001.
Compact
[3] Sekido M., Kondo T., Eiji K., and Imae M., Comparison VLBI, submitted to Radio Sci., 2000.
VLBI
of ionospheric
Network
delay obtained
[4] Koyama Y., Microwave flux density variations of compact radio sources monitored long baseline interferometry, Radio. Sci., in printing (RS2398), 2001. [5] MacMillan, D.S., Atmospheric gradients Res. Lett., 22, 1041-1044, 1995.
2000
IVS Annual
Report
Around
from very long baseline interferometry
the Tokyo by GPS and
by real-time
observations,
very
Geophys.
213
CRL
Analysis Center
[6] Chen, geodetic
214
G.
and data,
Kashima
T.
A.
Herring,
J. Geophys.
Effects Res.,
102,
of
Space Research Center, Communications
atmospheric
20489-20502,
azimuthal
asymmetry
on
Research Laboratory
the
analysis
of space
1997.
2000 IVS Annum
Report
..
1+
55 57 DGFI Analysis Center _ _
DGFI, Deutsches Geod/itisches Forschungsinstitut
DGFI
Analysis
Volker
Center
Tesmer,
Hansj6rg
Annual Kutterer,
Report
Hermann
2000
Drewes
Abstract This report summarizes the activities of the DGFI Analysis Center from March 1999 to the end of 2000. The report contains planned activities for the year 2001, too.
1.
Special
Analysis
Center
Operation
The Deutsches Geod/itisches Forschungsinstitut (DGFI) is a non-governmental research institute under the auspices of the Deutsche Geod/itische Kommission (DGK). It is housed at the Bavarian Academy of Sciences (BAdW) in Munich. DGFI is financed by the State of Bavaria. The general task of the IVS Analysis Center at DGFI data analysis and to generate VLBI products, in particular
is to support and to improve the VLBI Earth rotation parameters (see DGFI
web serverhttp ://www. dgfi. badw. de). 2.
Initial Since
Activities the beginning
1. Modification
of IVS, DGFI
of the OCCAM
has carried
VLBI
station
of the
coordinates
Scherneck
(www.oso.chalmers.se/_hgs);
correction
of thermal
antenna
due
to atmospheric
deformation,
new model (2000);
according
of solid
Earth
of all NEOS-A,
Systematic different 3. Analysis
differences networks
CORE-A, between
reach
CORE-B
the series
190 mas (Tesmer
of the 58 simultaneous
NEOS-A
were detected. Schuh,
and
CORE-A
published
by H.G.
et al. (1999);
which
will be included
in the
following the Gauss-Markov of Technology, Vienna).
and IRIS-S
and
loading,
to Haas
tides,
extension of OCCAM by a least-squares approach (in cooperation with J. BShm from the University 2. Analysis
activities:
software
correction
implementation of the next IERS Conventions
out following
sessions The
between offsets
model
1997 and 1999
between
results
from
2000). sessions
between
1997 and
1999
Differences were found between EOP derived from the two completely independent networks observing simultaneously, which were occasionally two times greater than their formal errors (Tesmer and Schuh, 2000). They (1999) who used the CALC/SOLVE 4. Considering Comparisons and 'usual' correlations greater and
a-priori
correlations
are very similar to those software package.
in VLBI
data
obtained
by MacMillan
et al.
analysis
between solutions with a full variance-covariance matrix of the observables solutions with the off-diagonal elements set to zero showed that taking a-priori into account yields hence more realistic
the repeatability 2000 IVS Annual Report
of the parameters
formal errors of the results of a single session which are than those from an 'uncorrelated' solution. Additionally, improved
significantly
(Schuh
and Tesmer,
2000). 215
DGFI Analysis Center
DGFI, Deutsches Geod_tisches Forschungsinstitut
5. Development of a Knowledge-Based System for the SOLVE (Schwegmann and Schuh, 1999, Schwegmann 3.
automation and Schuh,
of VLBI 2000).
data
analysis
by
Staff DGFI
personnel
involved
in the IVS Analysis
Hermann Changes
in personnel:
In April
2000, Harald
Drewes,
Schuh,
HansjSrg
Head
4.
Schwegmann
are the following
Kutterer
of the Earth
full professor at the University of Technology at the University of Technology Karlsruhe. In May 2000, Wolfgang tronomia, Bologna.
Center
and Volker
Rotation
Vienna.
left the DGFI
January
2001):
Tesmer.
Section,
His successor
(status
left the DGFI
is HansjSrg
for a position
to become
Kutterer,
at the Istituto
formerly
di Radioas-
Plans For 2001 the plans • Further
of DGFI
improvement
Analysis
Center
are:
of OCCAM:
OCCAM will be updated to be in full agreement with the IERS Conventions (2000). The parameterisation will be extended. All changes will be done in cooperation with the VLBI groups of Saint-Petersburg (J. BShm). • Contribution
to the VLBI
University terrestrial
(O. Titov) reference
It is planned to compute a terrestrial equations of all usable VLBI sessions of offsets
• hlrther
on the stochastical
• Investigations
of subdiurnal
• Generation of IVS products on data analysis.
between
variations (EOP
EOP
series
model of Earth
and
TRF)
of Technology
Vienna
accumulating
normal
frame:
reference frame with from 1979 till present.
• Further investigations network. investigations
and the University
which
OCCAM,
depend
used in VLBI orientation
on the particular
data
analysis.
parameters.
and contribution
to the IVS Working
Due to the move of W. Schwegmann to Bologna, the work on the development Based System for the automation of VLBI data analysis will not be continued the Istituto di Radioastronomia, Bologna.
5.
Group
of a Knowledgeat DGFI, but at
References Haas,
tenna
216
VLBI
R., Nothnagel,
Deformation"
A., Schuh,
H., Titov,
of the IERS Conventions
O.: Explanatory
(1996).
In: Schuh,
Supplement H. (Ed):
to the Section
Explanatory
"An-
Supplement
2000 IVS AnnualReport
a
DGFI, Deutsches Geod_tisches Forschungsinstitut
to the IERS Conventions port
No. 71, 26-29, MacMillan,
Clark,
T.A.,
D.S., Himwich,
W.E.,
6 and 7, Deutsches dgfi.
Thomas,
High-Accuracy
13th Working
badw. de/dgf
Meeting
C.C., Earth
Geod£tisches
Vandenberg, Orientation
on European
Forschungsinstitut
±/DOC/report71.
VLBI
N.R., Bosworth, Measurements.
for Geodesy
Re-
pd_f J.M., In:
Chao, B.,
Schliiter,
and Astrometry,
W.,
166-171,
1999
Schuh, 34(4),
Chapters
1999, http://www,
Ma, C.: CORE,
Hase, H. (Eds): Viechtach,
(1996)
DGFI Analysis Center
H.: The Rotation
421-432,
Schuh,
of the Earth
Observed
by VLBI.
Acta
Geod.
Geoph.
Hungarica,
Vol
H., Bosch,
W.,
1999
H.: Contributions
of VLBI
to Space Geodesy.
In: Rummel,
R., Drewes,
Hornik, H. (Eds): Proceedings of the international syposium 'Towards an Integrated Global Geodetic Observing System', Munich, Oct. 1998, Springer IAG Symposia series Vol 120, 33-40, 2000 Schuh,
H.: Short-period
Variations
of Earth
Rotation
Observed
by VLBI.
In:
Soffel M., Capi-
taine N. (Eds): Journ. 1999 and IX. Lohrmann-Kolloq., 'Motion of Celestial Bodies, Astrometry and Astronomical Reference Frames', Proc., Obs. de Paris, UMR 8630, CNRS, 197-205, 2000 Schuh,
H.: Geodetic
eral Meeting Schuh, denberg, 237-242,
H., Tesmer, N., Baver, 2000
Schuh, VLBI. In:
Analysis
Proceedings,
Overview.
In: Vandenberg,
NASA/CP-2000-209893, V.: Considering
K. (Eds):
A Priori
IVS 2000 General
219-229,
N., Baver,
Correlations Meeting
in VLBI Proceedings,
H., Titov, O.: Short-period variations of the Earth Schliiter, W., Hase, H. (Eds): 13th Working Meeting
and Astrometry,
172-177,
etry, 265-272,
Viechtach,
IVS 2000 Gen-
Data
Analysis.
as seen by for Geodesy
H.: On the Automation of the MarkIII Data Analysis 13th Working Meeting on European VLBI for Geodesy
System. In: and Astrom-
1999
1999 Schuh, H.: Status of IADA: an Intelligent Assistant for Data N., Baver, K. (Eds): IVS 2000 General Meeting Proceedings,
2000-209893,
2000
Tesmer,
V., Schuh,
H.: Comparison
Tomasi, P., Mantovani, F., Perez European VLBI for Geodesy and
2000 IVS Annual Report
Van-
NASA/CP-2000-209893,
Schwegmann, W., VLBI. In: Vandenberg, 319-323,
In:
rotation parameters on European VLBI
Viechtach,
Schwegmann, W., Schuh, Schl/iter, W., Hase, H. (Eds):
K. (Eds):
2000
of the Results
Obtained
by Different
VLBI
Torres, M.(Eds): Proceedings of the 14th Working Astrometry, Istituto di Radioastronomia, Bologna,
Analysis in NASA/CP-
Networks.
In:
Meeting on 7-12, 2000
217
6 15 FFI Analysis
Center
Forsvarets
Combination
forskningsinstitutt
of VLBI,
GPS Per
and
Helge
(FFI)
(Norwegian
SLR
Data
Defence
Research
Analysis
Establishment)
at
FFI
Andersen
Abstract FFI's contribution to the IVS as an Analysis Center will the observation level of data from VLBI, GPS and SLR using summarises the current status of analyses performed with Analysis Center for IVS and ILRS, Technology Development Center for IERS.
1.
Introduction Recently,
a number
established. and
be
of the
accordance parameters present
a constant a priori
(EOP)
estimated.
The
which
help
will
more
accurate
of SLR
in the
de-correlation
Data
be referred the
analysis.
The the
orientation
the
level
estimated
218
at the
the
is independent many
of Earth
from
all involved atmosphere
vapour,
solve-for
at the
observation
FFI
during
the
last
has
been
velocity station
constraints
data
types.
which
gives
in
orientation The
must
be
new information
parameters
advantages
data by
set
been
colocated
colocated
One
of the
other
more
of the
same each
using
of water
and
and
point
have
the for
is estimated
surveys.
content
with
velocities
reference
be estimated water
move
and
antennas
ground
can
geodetic
1993 to September analysis.
data
A second
for Lageos
observation were into
software
Station
level
performed
[1]. The
VLBI and
I and
1999 analysis
Lageos
using
and
lead
with
the
combination
level,
are
fully
to of
accounted
15 years.
the
analysis
and model
were
analyzed. same
strategy
using
the
and
strategy
combined
VLBI-alone
software.
and
SLR
are
simultaneously
will
analysis
was
as for the VLBI
analysis
analysis
combined
period
GEOSAT
a combined
estimated
This
to as the
the
same
of 24 hours
VLBI-alone
velocities
referred
II from
exactly
in arcs
a multi-year
coordinates
show
that
polar UT1
nutation
the
motion
parameters
mas.
that The
use
of SLR
parameters from
parameters
indicates
of 0.05-0.08
to a few
station
technique
The
solution
described
with
the
in
Earth
parameters. results
parameters
by
[2] developed
January
SLR
combined
estimated
estimated
space
from
analyses
CSRIFS [3].
The
data two
were
Andersen
of the
These,
VLBI-alone
where
VLBI
arc-results using
data
to as the
performed
with
the
of atmospheric
estimates. software
colocated
colocated
is the
which
one observation
Analysis
A set of VLBI was
data,
complementary
GEOSAT
given
than
of coordinates from
of the
of VLBI
inclusion
and the
set
coordinates
source
parameter
independent for with
geocenter
error
more
vector
centers
information
and
dominating
one
eccentricity
phase
with
at a given
to determine
individual
with
stations
all instruments
possible
In addition,
to each
of colocated
In principle,
it should
site.
2.
focus primarily on a combined analysis at the GEOSAT software. This report briefly the GEOSAT software. FFI is currently Center for IVS, and Combination Research
from
the
analyses
from
10 to 0.2-0.3
precision
data
0.2
mas
to VLBI to 0.1
5 microseconds, mas
of these show
in addition
that
to 0.15
and mas.
The
mas,
improves
it improves
it improves formal
parameters
in principle
the
VLBI
applied
data
and
the
precision could SLR
the the
precision
precision
precision of the
of the nutation
be improved models
are
of
to the
consistent
mm.
2000 IVS Annual
Report
Forsvarets forskningsinstitutt
The results
indicate
(FFI) (Norwegian Defence Reseaxch Establishment)
that
basis it might be better rather than daily VLBI
(or reducing)
Earth orientation It is observed
the
high precision investigations periods
parameters. from the solutions
can lead to changes
of two Lageos
satellites
while
with no VLBI for the radio
data
on the precision
source
up to 0.3 mas in the estimated
the standard
positions
source
that
deviation
in declination
at the observation
level.
Furthermore,
of the
is significantly
estimates
the inclusion
coordinates.
of the
of SLR data
This is not unexpected objects in addition to the in the formal uncertainties with the inclusion of SLR
improved
as a factor of four. This will be further investigated. The results show that for the first time VLBI and SLR tracking combined
on a daily
estimates of these parameters for days where VLBI data are necessary in order to determine the consequence of
since the two Lageos satellites used in the present analysis are physical radio sources being used for the realization of CRF. It is a general trend that the standard deviation in the right ascension is slightly improved data
is available
to have, say 3-4 VLBI sessions a week, with many participating stations sessions with a small number of participating stations. The SLR data are
fully capable of producing axe not available. Further enlarging
as long as SLR tracking
FFI Analysis Center
in some cases by as much
data
it is the first time satellite
have
been
tracking
successfully data
success-
fully have been used for the direct determination of nutation parameters. Based on the analysis and preliminary experience with the combination of VLBI, SLR and GPS data the author is convinced that the direct combination of high precision space geodetic data at the observation level within ten years will be the primary frames and their interrelations. More details
3.
of the analysis
can be found
for the realization in Andersen
of terrestrial
and celestial
reference
[4].
Prospects In the near future
with the VLBI 4.
method
Technical Table
GPS data
for selected
and the SLR data
days will be incorporated
at the observation
in the analysis
and combined
level.
Staff
1 lists the FFI staff involved
in IVS activities.
Table 1. Staff working at the FFI AC and TDC
2000
IVS
Annual
I Name
I Background
I Dedication
I Agency
I
I Per Helge Andersen
I
I
t
I
Report
geodesy
40%
FFI
219
FFI AnalysisCenter
Forsvarets forskningsinstitutt (FFI) (NorwegianDefenceResearchEstablishment)
References [1] Andersen, 531-551.
P. H. Multi-level
[2] Andersen, P. H. NDRE/Publication [3] Andersen, preparation.
arc combination
High-precision 95/01094.
P. H. Combined
station
analysis
with stochastic
positioning
of VLBI,
GPS
parameters.
and
satellite
and
SLR
[4] Andersen, P. H. Determination of Earth orientation parameters at the observation level. Invited paper submitted 15 May, 2000, issue on the theme "New methodologies for EOP combinations"
220
Journal
orbit
data
at
of Geodesy
determination.
the
observation
(2000)
PhD
level.
74:
Thesis,
Under
using VLBI and SLR data combined to Journal of Geodesy for the special
2000 IVS Annual
Report
2... ...... "" 55576 q Geod_itisches Institut
der Universit_it
The
Bonn
GIUB/BKG
GIUB/BKG
Axel
Nothnagel,
VLBI
Volkmar
Analysis
Center
Gerald
Engelhardt
Thorandt,
Analysis
Center
Abstract This report describes the activities of the GIUB/BKG VLBI Analysis Center during the reporting period. Data analysis activities and the development of data analysis technology are described. Past and on-going research topics are reported. Finally, center personnel are listed.
1.
Overview The
GIUB/BKG
Kartographie Bonn own
VLBI
und
(GIUB).
Both
analysis
Analysis
Center
(BKG),
Leipzig,
Geod_ie institutions
groups
closely
in Leipzig
and
has
been
and
cooperate
Bonn.
estabished
by
the
in the
The
jointly
Geodetic field
by
of geodetic
responsibilities
the
Institute
include
Bundesamt
of the VLBI
data
ffir
University
maintaining
analysis
of their
and
software
development. Both nated
groups
to increase
2.
the
has 190
GByte
disc
have
sessions) in 1999
Madrid
CALC/SOLVE/GLOBL software
several
new
once
Polarization
is being
9000/D280/1
been
used
has been
which modified
origi-
extensively
features.
for routine
computer
analysed
Crustal
(EU and
Project
Yebes,
per year
and
jointly
(HP
VLBI
UX
10.20
and
BKG
data
processing.
operating
The
system)
with
GIUB
in Europe
by
since
the
beginning
of
VLBI
FMRX-CT960071) in 2000
with
Medicina, the
at
Motion
7 sessions
(DSS65),
its testing
the
Matera
mobile
unit
stations
and
NyAlesund,
Noto
have
TIGO-WTZL
been
Onsala, processed.
participated
Wettzell, Effelsberg
at several
occasions
phase.
tests
In order
to investigate
in which
several
circular
polarization
cross-polarization • International Twelve
to add
package
on a HP
of Vertical
participated during
and
software
SOLVE/GLOBL
space.
sessions
Six sessions
analysis
basic
speed
installed
Measurement
Simeiz,
data
the
Activities
(EUROPE
polarization
impurities
swapped
polarization
stations
(LCP) scans
Radio
sessions
Westford •
III/IV
CALC9.11/f-SOLVE
been
The following March 1999:
•
Mark
At GIUB
Analysis
At BKG software
•
the
its computational
Data
about
use
at NASA/GSFC.
were
Continuous
per
while
were
other
detected
and
with
the
regular
from
stations
Interferometric year
two
the
right
circular
continued analysis
Surveying stations
EUROPE to
was
polarization observe
RCP.
were
extended
(RCP) Fringes
to left at
all
completed.
- South
Wettzell,
sessions
HartRAO,
(IRIS-S): Fortaleza,
Fairbanks
and
processed. Observations
of
the
Rotation
of
the
Earth
-
O'Higgins
(CORE-
OHIG)
2000 IVS Annual
Report
221
GIUB/BKG
•
AnalysisCenter
Nine
sessions
been
analyzed
Annual In
with
Geod_itisches Institut derUniversit_it Bonn
stations
in 1999
Solution
addition
and
for
to
the
HartRAO,
are
and
estimated
Submission
session
by
Reference
Frame
parameters covariances ITRF •
to
session
•
IVS
EOP
After
the
residuals to the The
final
and
Celestial
solution
frequency fixed annual submission
solution
Earth
DSS45
have
is computed
cooper-
station Mark to the IERS.
III data Station
orientation
types
are
Reference
to the
calibrated
parameters
bkgtra99
Frame
and
for the
(EOP)
the
Earth
Terrestrial orientation
Station coordinates, velocities and SINEX format and submitted to the
ITtLF2000
databases
Correlator
of the
procedures area
processing is the
and
realization.
and
for most
of the
subsequently
sessions
submitted
correlated
them
to the
at IVS
the Data
series
incoming
at BKG
combined
positions The
for the
III/IV
preprocessing and
Kokee
output
generated
time
source
as a contribution
Bonn Astro/Geo Mark Centers for distribution.
one
from the IVS Data Centers. solution were converted into
of correlator group
analysis
solution.
bkgira99
of IERS
Processing BKG
and
Hobart,
IERS
most of the dual is the basis for the
radio
global
are available of the TRF
Section
The
velocities, in one
Fortaleza,
2000.
atively each year which comprises available worldwide. This solution coordinates
O'Higgins,
basis
individual
for outlier of the
VLBI
elimination
BKG
IVS
of individual
VLBI
for producing
two
Data
sessions the
Center
sessions EOP
and
into
(IRIS-S,
time
which
databases
includes
and the
local
EUROPE,
series
regularly
inspection
related
files
data
of the
are
uploaded
area.
COHIG,
NEOS,
submitted
CORE)
to the
IVS
Data
Centers: -
bkg00001.eops
-
bkgint01.eopi
generated
from
generated
from
Table
1. Mean
2360 UT1
ffxwob aywob _utl ad_ _de
The
corresponding
and
2000
descriptions
222
values three.
is 22.0 which
#s.
The are
for The
the mean
features
available
VLBI
intensive
formal
Component
of approximately
24h
sessions
errors
between between
1999-2000 0.223 mas 0.213 mas
33.8 #s 0.764mas 0.256mas
13.6 #s 0.212 mas 0.085 mas
span
from
formal
error
of the
solutions
IVS
Data
1984 1999
and
and
2000
2000
for 24 h sessions
1984-2000 0.618mas 0.641mas
time
in the
sessions
1999
for the are Centers
to 2000
have
intensive
experiments
described in the
in the directory
improved
by
a factor
between
respective
1999
technical
ivsdocuments.
2000 IVS AnnuM Report
Geod_itisches
3.
Institut
der
Development
Universit_t
Bonn
of VLBI
Data
• One of the responsibilities for export
GIUB/BKG
Analysis
of the GIUB
Center
Technology analysis
in the form of Mark III data
Analysis
group
analysis
is the preparation
system
databases
of correlator
for the sessions
data
correlated
at the Bonn Astro/Geo correlator center. In most cases this task is straightforward but sometimes it requires some extra efforts. The main reason for additional interaction is radio frequency interference which may saturate individual channels causing some of the delay observables
to be corrupted.
In this case
the
fringe
fitting
process
may
select
the
wrong
peak of the delay resolution function and produce an incorrect delay observable. However, this fact can only be detected when a least squares solution is computed with the program SOLVE. In a subsequent step the residuals of the SOLVE run can be used to narrow the search window in a repeated fringe fitting process. A semi-automatic procedure for this task is available at GIUB. • Semi-automatic
Web-presentation
ports of all VLBI the Web between man-power • Internal data
part
4.
results
is being
developed.
Detailed
re-
available.
logic of the software
• In order program
analysis
data processed at the GIUB/BKG Analysis Center have been displayed on 1998 and the middle of 2000. This task will be resumed when additional
becomes
processing
of data
SOLVE
and to expand
was updated
the capabilities
in order
to reduce
of the analysis
overhead,
to speed
up
system.
to make the analysis processes more effective the BKG group developed its own environment around the CALC/SOLVE software automating the post interactive
for establishing
Research
the two EOP series
mentioned
above.
Topics
• Determination
of telescope
The Medicina surveys before
telescope and after
displacements
by local
engineering
work
at Medicina
has been displaced slightly in 1996 due to track repairs. The local the displacements were analysed (NOTHNAGEL AND BINNENBRUCK
2000). • Footprint
measurements
In the framework order
at
Ny/klesund
of a footprint
to determine
project
the coordinates
local measurements
of the antenna's
network of concrete pillars. Preliminary analysis local eccentricities between the VLBI antenna and when the Norwegian • Joint
least
At DGFI
squares
• Investigation An extended Conditions
2000
IVS
Annual
VLBI data
of the set of VLBI solutions
Report
geodetic
sessions
and
VLBI
of using
relative
to a local
phase
its GPS analysis.
at the level of observables
and solutions
has been re-analyzed
can be resolved
point
in
observations
measurements
preprocessing
feasibility
reference
out at Ny Alesund
of the measurements has occurred, and the IGS GPS antennas will be computed
will have completed
of GPS
of space
when ambiguities
delay
Authority
adjustment
a combination
carried out. Special of this research.
phase
Mapping
VLBI
were carried
delays
are performed
at GIUB
in geodetic
for resolving
as well as differences
phase between
is being in support
VLBI delay ambiguities. group
delay and
were investigated.
223
GIUB/BKG Analysis Center
Correlator
Geod_itisches Institut der Universit_it Bonn
comparison
In order to investigate in greater detail the MK III/MK IV correlator performance, a 4-station IRIS-S session has been correlated both at the old MK IIIa and at the new MK IV correlator. In fact, before the definitive closing down of the MK IIIa correlator, two complete independent correlations of the same IRIS-S sessions were carried out to establish floor of the old system.
First
results
of the comparison
have been
published
and fully the noise
(Mi)SKENS et
al. 2000). 5.
Personnel
Table 2. Personnel
at GIUB/BKG
Klaus BSrger Gerald Engelhardt Axel Nothnagel Leonid Petrov Christoph Steinforth Volkmar Thorandt Dieter Ullrich
GIUB BKG GIUB GIUB GIUB BKG BKG
Analysus Center I until 11/2000 t I ] until 4/2000 t
References Miiskens
A., K. B6rger,
M. Sorgente,
J. Campbell
(2000):
Comparison
of Mk III and MK IV Cor-
relation Using a J-station IRIS-S experiment; Proc. of the 14th Working VLBI for Geodesy and Astrometry, Castel San Pietro Terme, 125-136
Meeting
on European
Nothnagel, A., B. Binnenbruck (2000): Determination of the 1996 Displacement of the Medicina Radio Telescope by Local Surveys; Proc. of the 14th Working Mecting on European VLBI for Geodesy
and Astrometry,
Castel
San Pietro
Terme,
61-66; available
under
http://giub.geod.uni-
bonn.de/vlbi/publications
224
2000 IVS Annual Report
555"770 NASA
Goddard
Space
Flight
Center
Goddard
GSFC David
Gordon,
VLBI Chopo
Analysis
Ma,
Leonid
Space
Flight
Center
Analysis
Center
Center
Petrov,
Dan
MacMillan
Abstract This March
report 1, 1999
research
presents
the
through
activities
activities
December
are
of the
31, 2000.
reported,
and
the
GSFC
The
VLBI
center's
responsible
Analysis
primary
staff
Center
software
members
are
during
the
development,
described.
Plans
period
from
analysis
and
for 2001
are
also presented.
1.
Introduction
belt,
The GSFC VLBI Analysis Center MD. GSFC analyzes all geodetic
for all NASA/GSFC
and
USNO
is located at NASA's Goddard and astrometric VLBI sessions
sessions
within
24 hours
Space Flight and submits
or less of their
Center in Greendatabases to IVS
correlation.
The
group's
main thrust is the operation and analysis of the CORE experiments and the gradual expansion of CORE into a full time EOP monitoring program. The group processes all 24-hour sessions from the Mark 4 correlators and submits EOP values derived from each session within 24 hours of correlation.
The group
also analyzes
within 2 hours of correlator velocities as well as source
NEOS
Intensive
experiments
and submits
the UT1
values
release. Additionally, GSFC periodically submits station positions and coordinates from global solutions using all available VLBI observations.
The analysis group also processes all VLBA RDV sessions using the NRAO AIPS program. GSFC uses, maintains, develops, and distributes the Calc/Solve analysis system. The also engages in research and analysis standing of Earth rotation, improving sphere 2.
modeling,
and maintaining
activities aimed at improving the nmasurement and VLBI analysis techniques and modeling, improving
and refining
and
terrestrial
reference
frames.
Activities The primary
software
development
• Program Calc was upgraded to fix a minor error. • F-Solve groups'
development Solve versions
activities
to versions
• Developed Centers
was moved from were consolidated.
an automated
• Developed databases • Began
system
and the IVS Analysis
GIUB/BKG
an automated to IVS (program
bimonthly
bution
IVS Annual
kit.
Calc/Solve
Considerably
Report
system opa).
1, 1999 - Dec.
in April
updates,
EOP
in the
Calc/Solve
dclient, and
form
system
tide option
2000,
to support
between
dserver,
for generating
the
to GSFC
transmission
31, 2000 included:
the permanent
Solve were made
(programs
system
increased
and
for data
Centers
from March
9.1 and 9.11 to add
• Extensive changes in programs Dbedit data from the new Mark 4 correlators.
2000
the celestial
group undertropo-
correlators, geo_export submitting
and
the
two
the processing
of
the
IVS Data
and geo_import). EOP
series
of an easy-installation documentation.
and
and
distri-
Currently
44
225
Goddard Space Flight Center Analysis Center
Calc/Solve documents begun at GIUB/BKG • Developed phase The
software
cal signals.
primary
• ICRF-Ext.1,
are available from http://gemini.gsfc.nasa.gov/solve. and moved to GSFC in April 2000.) for analysis
(Begun
analysis
NASA Goddard Space Flight Center
of phase
at GIUB/BKG
activities
during
the first extension
data from July 1995 to April and introduced small modeling ICRF.
calibration
errors
and moved
the period
and
to GSFC
(An
for correction
in April
activity
of spurious
2000.)
included:
of the ICRF,
was produced
1999. This improvements
solution added 59 new sources to the consistent with the stated uncertainties
in mid 1999 to include
additional catalog of the
• Two solutions were generated as input to ITRF2000. Tile first submission, gsf1122, in the Spring of 2000 (CALC 8.2/S-Solve) included data through the end of 1999. Based on the discussions at the ITRF2000 workshop, a second solution, gsf2000b, was made at the end of 2000 (CALC through
9.1/F-Solve)
October
which
incorporated
additional
Asian
stations
as well as data
2000.
• Began manual database automated submissions
submissions within in October 2000.
24 hours
to IVS in June
1999.
Upgraded
to
• Began manual EOP-S weekly IVS submissions (polar motion, UT1, and nutation) in September 1999. Upgraded in October 2000 to automated submissions within 24 hours of correlator release. • Began NEOS-Intensive in November 2000. • Analysis activities June 2000. • Assumed Intensive • Submitting The primary
session
analysis
were shifted
the initial
analysis
experiments
and
• Investigated the precision derived from simultaneous ries for the period
data
from the USNO
activities
EOP-I
from CalcS.2/S-Solve
all old (1979-1998) research
and automated
submission
analysis
for NEOS-A
and
in
NEOS-
2000.
to IVS, approximately
the period
series IVS submissions
to Calc9.1/F-Solve
responsibilities
in December
databases during
analysis
(UT1)
included
two-thirds
completed.
the following:
and accuracy of daily VLBI EOP estimates. Two EOP series CORE and NEOS sessions were compared with an IGS GPS se-
1997-2000.
The
level of bias between
the VLBI
networks
is greater
than
expected and is most likely due to an error in the underlying TRF. Based on 3-corner hat comparisons between the two simultaneous VLBI series and the GPS series, the observed precision of polar motion (80-120 #as) from the three series is similar, although better. Several sources of unmodeled or mismodeled station position error the EOP loading, • Continued
error
are being
and hydrology investigations
examined,
for example,
tidal
ocean
loading,
GPS is somewhat that contribute to
atmospheric
pressure
loading. using
meteorological
data
assimulation
models
to improve
VLBI
tropospheric delay modeling. Use of a priori mean site gradients reduces systematic error both the CRF and the TRF. Use of a priori 6-hour gradients yields some improvement repeatabilities. in repeatabilities. 226
Mapping
functions
based
on raytracing
of model
profiles
yield
in in
improvement
2000 IVS Annual Report
NASA Goddard Space Flight Center
Goddard Space Flight Center Analysis Center
• Examined signatures in corresponding VLBI and GPS baseline length and site time series. An error budget summarizing the remaining unmodeled error was developed. Spectral analysis indicates that there are annual and semi-annual signatures in many of the VLBI series, but the VLBI and GPS signatures are only similar for some sites. • Investigated estimates. pare VLBI of VLBI
the determination of high frequency Collaborated with Markus Rothacher and GPS tidal amplitudes
and
• Developing parameters, Examined a nutation glecting
GPS hourly
ondary
and to determine
mutual
from a combination
a two-step approach, in which are estimated separately, ne-
correlations.
Love numbers
for long period
the feasibility
tides from VLBI
of an arc-length
approach
observations.
for the
selection
of primary
and
sec-
sources.
• Made a correlator
comparison
study
of Mark 3 versus
experiment. Results indicated an error source larger comparison of Mark 4 versus VLBA/AIPS • Began collaboration experiments. 3.
tidal amplitudes
series.
methods for the direct estimation of nutation expansion coefficients, precession and high frequency EOP amplitudes and phases in a single combined solution.
their
• Investigated
GPS
tidal amplitudes from hourly EOP VLBI (Technical University of Munich) to com-
the differences between a combined solution versus time series and the nutation expansion coefficients
• Estimated
and
with
NRAO
on astrometric
VLBA/AIPS
processing
on the VLBA/AIPS in RDV22. analysis
of the
side.
VLBA
in the RDVll Preparing
calibrator
for a
survey
Staff The
GSFC
analysis
group
is part
of a larger
VLBI
group
of civil servant
sonnel, led by Dr. Thomas A. Clark, which also includes a Technology Network Stations, the CORE Operation Center, and the Coordinating is composed activities.
of the following
Dr. Chopo Ma leads restrial reference frames,
six individuals
who are involved
and
contractor
per-
Development Center, three Center. The analysis group
full time,
or nearly
the analysis group. His interests include as_rometry, extension and improvement of EOP measurement,
so, in analysis
the celestial and terand the improvement
of analysis and modeling. He is a member of the IAU working group on the Celestial Reference System and heads the subgroup for the maintenance and extension of the ICRS. As such he has particular interest in improving the modeling and optimization of ICRF analysis as well as providing better
information
about
source
position
variations.
He is also one of the VLBI
on the IERS directing board, and is responsible for generating ITRF and IERS use and for improvement of consistency between them. Dr. Dan MacMillan (NVI, Inc.) system software development (Solve), interests functions
is involved particularly
and ICRF
for IVS
in VLBI technique improvement and analysis in the area of tropospheric delay modeling. His
include improving the modeling of atmospheric delay gradients, from meteorological assimilation data, and various TRF and
working on improving or adding modeling for atmospheric pressure hydrology loading. He is also studying differences in EOP derived
2000 IVS Annual Report
representatives products
deriving better mapping CRF studies. He is also
loading, ocean loading, and from different simultaneous
227
Goddard
Space
Flight
Center
Analysis
VLBI networks and GPS EOP and GPS estimates. Dr.
David
Gordon
Center
in order
to assess
ITSS)
manages
(Raytheon
performs the AIPS geodetic Calc. His research interests
NASA
accuracy
all initial data
processing of VLBA experiments, include astrometry, global and
VLBI modeling, improving VLBA/AIPS and phase delay development. Dr. analysis
the observed
processing,
Goddaxd
Space
Flight
and precision
processing
Center
of the VLBI
and analysis
activities,
and maintains and develops program regional tectonic motions, improving
correlator
support,
correlator
comparisons,
Leonid Petrov (NVI, Inc.) moved from the GIUB/BKG analysis group to the GSFC group in April 2000. He maintains and develops the Mark 4 VLBI analysis software
Calc/Solve
and the suite of programs
research in the fields of optimal the modeling of ocean loading, Ms. Karen Bayer (Raytheon
for automated
data
transmission
and processing.
He conducts
estimation of EOP, estimation of Love numbers, improvements in and investigation of instrumental errors in VLBI. ITSS) maintains and develops a wide range of software, including
the database and solution archive catalog systems, the SNOOP reporting programs, and various analysis graphics programs. She also supports the group's web page activities, assists in generating all types of TRF and CRF reports, publications, and provides assistance Ms. ing and 4.
Cindy Lonigro (Raytheon provides analysis support,
generates site and to new and current
ITSS) works on initial experiment preparation web page support, and miscellaneous support.
and data
IVS archiv-
Outlook Plans
for 2001 include:
• Calc/Solve: Develop source function (IMF). Incorporate and compare
structure correction mapping functions
with the Niell IMF mapping
and three dimensional atmospheric pressure ries. Implement new schemes for estimating IERS 2000 Conventions. Modify as necessary • Collaborate
on the development
• Make a comparison RDV22 experiment. processing. • Complete
228
velocity plots, assists in generating users of the analysis package.
capabilities. Add the Niell isobaric derived by raytracing atmospheric
function.
Test effects
of hydrology
mapping profiles
loading
of a new database
format.
study of Mark 4/Fourfit versus VLBA/AIPS correlating/fringing Also compare and study Mark 3 versus Mark 4, and K4 versus
the astrometric
analysis
series
loading (from loading convolution method) seEOP. Update as necessary for compliance with for HPUXll.0 on an HP9000/785 workstation.
of the VLBA
Calibrator
survey
in the Mark 4
experiments.
2000
IVS
Annual
Report
.; _ L
/
7_F
MIT
,, /,,.i
._5?72
/
Haystack
Observatory
Haystack
Analysis
and
Research
at
Arthur
Niell,
the
Haystack
Brian
Observatory
Analysis
Center
Observatory
Corey
Abstract New mapping incorporated function
discrepancies
1.
Geodetic
the
The
primary
derlying
models
at
objectives in order
model
VLBI
Research
error
and
the
accessible
at Haystack. budget
on how to utilize
A better
between
easily
package
vertical
initiated
satellites.
incorporate
analysis
to the
has been
GPS
that
solvk
contribution
A study of the
functions
in the
for
GPS
to obtain
is significantly
and
latitudes
have the
been
mapping
reduced. understand
GPS
satellite
phase
center
reference
frame
scales.
terrestrial
information
high
to better
the
the
antenna
will
help
characteristics resolve
possible
Observatory
activities
better
middle
VLBI
Haystack
of analysis
in situ atmospheric For
at Haystack
accuracy
and
Observatory
precision
are to improve
and
to better
the un-
understand
the
uncertainties that limit the space geodetic techniques. Since there are many similarities between VLBI and GPS, it is natural to investigate both common error sources and and those that are unique in order to obtain the best results from both techniques. This has led us to study the atmosphere model, which receiver antennas of GPS. Atmosphere
can be applied
to either,
and
the characteristics
of both
satellite
and
models
Gridded
global
geopotential
numerical
heights
weather
of an isobaric
models
surface,
provide
in situ meteorological
for example
the
200 hPa
information.
surface,
serve
The
as a useful
parameter for the hydrostatic component of the mapping function [3]. The improvement relative to the widely used NMFh [2] is shown in Figure 1 for a mid-latitude site; the scatter of the mapping function at 5° is an indication of the error that will be introduced in the vertical. The improvement in modeling precision, latitude, is illustrated in Figure 2.
interpreted
as approximate
vertical
error
as a function
of
to raytraeing
of
ALB
80!
L_ o
NMFh-radiosonde
i_
40
o
,oo + +..
-80
_
-1°_2
o
o
'
-i992]2 -1_.4-
1_.6
1_28
"
1993
yc_
Figure
1.
radiosonde
2000
IVS
Temporal profiles
Annual
errors for
Report
the
of hydrostatic
mapping
IMF
hydrostatic
and
NMF
functions. mapping
The
difference
functions
at
with
respect
5 ° elevation.
229
Haystack
Observatory
Analysis
Center
MIT Haystack
--
,_ :-
i
+ x
IMFw IMFh
2
IMFw+IMFh NMFh+NMFw
Observatory
[
== HI ,,',
IE E
A _,Zx
I
_ 5
A.
x
x
+
+
_
4.'+
x
+ +._
4r.4++
+
O_ -81)
Figure
2.
Vertical
hydrostatic
error
induced
and wet mapping
elevation
of 5 °. The dashed
the expected height azld for NMF.
-51)
--10
by hydrostatic
functions
-20
20
mapping
to the vertical
lines are of the form
uncertainties
0 latitude
40
60
functions.
error
80
The approximate
for VLBI
or GPS
contribution
experiments
cos(2*latitude)
and
are intended
only to guide
hydrostatic
and
wet mapping
function
for the combined
The relative value of the two hydrostatic mapping functions has been tested the variation of the baseline lengths for the CONT94 VLBI data, assuming that
of the
with a minimum the eye to
errors
for IMF
by comparison of they are constant
over the short period of that campaign. The standard deviation of the lengths is slightly smaller using IMFh than using NMFh. No correction was made for atmospheric pressure loading, and, since this effect may have a comparable contribution to the scatter, this may account for the marginal improvement. VLBL
GPS,
and the Terrestrial
The direction-specific differs by antenna model.
Reference
Frame
instrumental delay The Dorne-Margolin
(phase center variation) of GPS ground antennas choke ring antenna has been assumed to be uniform,
but measurement of the phase pattern in anechoic chambers and by a rapid cycling among satellites by a "robot" [4] suggest a large elevation-dependent error. For this error to be reasonable the GPS satellites and
VLBI
must
in the
have a compensating
scale
of the
terrestrial
phase
error
reference
to avoid
frame.
a large
A joint
discrepancy
working
between
group
GPS
composed
of
representatives from the IVS, IGS, and ILRS and chaired by Brian Corey has been studying the feasibility of using differential VLBI observations of GPS satellites and nearby extragalactic sources to measure the phase pattern of the transmitted L1/L2 GPS signals. The aim is both to measure
the pt_ase center
locations
of the GPS phased
array
transmitters
and to "map"
the relative
magnitu(tes and phases of the drive voltages of the individual phased array elements. The required accuracy on the VLBI fringe phase is < 10 °, or < 5 mm in differential range, after correction for propagation media effects, extragalactic source position uncertainty, etc.; this level of accuracy will likely be difficult to achieve.
230
2000 IVS Annual
Report
MIT Haystack
2.
Observatory
Haystack
Observatory
Analysis
Center
Outlook Both
will The
of these
will
continue.
For
the
evaluation
of the
be updated with atmospheric pressure loading and with an amount of data will be extended to cover at least a full year
components Upon GPS
projects
in the
promising,
of the
antennas, funding
improved in order
models,
solvk
ocean loading to evaluate any
[1]
model. annual
results.
completion
satellite
atmosphere
will
study
a decision
to determine
the
feasibility
willl
on
whether
be made
of using
VLBI
to proceed,
and,
to characterize if the
project
the looks
be sought.
References [1] Herring, Kalman 12,581,
T. A., J. L. Davis, and I. I. Shapiro, Geodesy by radio interferometry: The application of filtering to the analysis of very long baseline interferometry data, J. Geophys. Res., 95, 12,5611990.
[2] Niell, A.E.: Global mapping Vol. 101, No. B2, 3227-3246, [3] Niell, A.E.: Improved (accepted), 2001.
functions February
atmospheric
for the atmosphere 1996.
mapping
[4] Wubbena, G. Schmitz, M., Menge, F., Boder, of GPS Antennas in Real-Time, Proceedings
2000 IVS Annual Report
functions
delay
for VLBI
at radio
wavelengths,
and GPS,
Earth,
J. Geophys.
Planets,
and
Res.,
Space
V. and Seeber, G.: Automated Absolute Field Calibration of the ION Meeting 2000, Salt Lake City, Utah.
231
,,._ j ;j
,_-°. -0o,.., :"55 577 f) IAA
Analysis
Institute
Center
IAA Zinovy
Malkin,
VLBI
Elena
Analysis
Skurikhina, Igor Surkis,
1.
of Applied
Astronomy
Center
Maria
Sokolskaya,
Iraida
Kozlova,
of Russian
Report George Yuriy
for
Academy
of Sciences
(IAA)
2000
Krasinsky,
Vadim
Gubanov,
Rusinov
Introduction
The IAA Analysis Center (IAA AC) is located at the Institute of Applied Astronomy of the Russian Academy of Sciences. The main fields of the activity include EOP service, computation of station and radio source coordinates, geodynamical investigations, comparison and combination of EOP, TRF and CRF realizations, development and comparison processing VLBI observations. IAA AC works in close cooperation 2.
of algorithms and software with IERS and IVS.
for
Staff Three VLBI groups of IAA contribute to IAA AC activity: 1. Lab of Space Geodesy and Earth Rotation: Dr. Zinovy
Dr. Maria Sokolskaya. the IAA EOP Service,
Malkin
(head),
Elena
Skurikhina,
The main tasks of this group related to IVS activity are: management of determination of EOP, station and radio source coordinates, comparison
and combination of VLBI, GPS, and SLR products. OCCAM for EOP and TRF computation, and ERA
The group explores two program packages: for EOP and (mainly) CRF computation.
2. Lab of Ephemeris Astronomy: Prof. George Krasinsky (head). The activity of this group is development of program package ERA for investigations and dynamical astronomy based on processing LLR, and optical observations. In particular, and SLR observations is under development. 3. Lab of New Methods
in Astrometry
main IVS related in Earth sciences
VLBI observations including combining VLBI, SLR, determination of EOP from combination of VLBI
and Geodynamics:
Prof.
Vadim
Gubanov
(head),
Igor
Surkis, Iraida Kozlova, Yuriy Rusinov. The main task of this group related to IVS activity is determination of EOP, station and source coordinates using new package QUASAR with emphasis on investigation of stochastic parameters (EOP, troposphere, clocks). 3. 3.1.
Analysis
Activities
EOP
service
IAA EOP Service based on regular processing of SLR and VLBI observations has been operating since 1994. Regular processing of VLBI observations started in 1996. Both operative and yearly final EOP series are regularly contributed is presented in Table 1. Along with EOP,
to both the IERS and the IVS. Accuracy station coordinates for every 24h session
In 2000 we started operative processing of the NEOS Intensives series. In 2000 two EOP final solutions EOP(IAA)00R01 (1984-1999) obtained and EOP(IAA)00R02 (1994 1999) obtained with ERA package have been 1999 Annual estimation
232
Report.
For all solutions
were practically
analogous
the
to those
model
of reduction
described
and
the
of these series are computed.
with OCCAM package submitted to the IERS method
in the IVS 1999 Annual
2000
of parameter Report.
IVS Annual
Report
9
i! ") t,_
Institute
of Applied
Astronomy
of
Russian
Academy
of
Sciences
Table 1. Accuracy of EOP series obtained Series (program) IAAo9907 (NEOS-A+CORE) IAAo9907 IAAi0011
3.2.
Radio The
source
IAA
Analysis
Center
with the OCCAM package for 1999-2000.
Xp, mas 0.19
Yp, mas 0.15
0.14 --
0.14 --
(NEOS-A) (NEOS-I)
(IAA)
UT1,
0.1 ms 0.09
A¢
sine, mas 0.13
0.07 0.22
Ae, mas 0.15
0.12 --
0.14 --
coordinates
computation
of radio
ERA package was continued IERS 1999 Annual Report.
source
catalogues
from global
processing
VLBI
of catalogs is advanced. The latest radio source catalog was transformed compared with ICRF-Ext.1. Result of comparison is presented in Figure A_ ,
,
observations
using
in 2000. Two catalogs of 312 radio sources have been submitted to the Moreover, the first version of software for comparison and combination
cos ,
6,
mas
A 6_
to the ICRF 1.
system
and
mas
o
2 1
1
0
0
-1
-1 •
-2 -3
-;0-;0-40-20
•
2;
4;
-2 6;
-3
S_0
-80
-60
-40
Figure 1. Differences of radio source coordinates A special study was performed to investigate on observational programs (NEOS-A - CORE-A). 3.3.
Processing
long
All available posphere in Figure
24h VLBI
zenith 2.
delay
time
series
sessions
time series.
VLBI
possible
-20
0
20
40
60
80
RSC(IAA)-ICRF-Ext.1. dependence
of radio
source
coordinates
observations
were processed An example
to obtain
session
of wet troposphere
station delay
coordinates
time series
and tro-
is presented
GILCREEK
O.1 O 1986
1988
1990
1992
Figure 2. Time series of wet zenith troposphere A series of UT1 based
2000
IVS
Annual
Report
for period
1984-2000
1994
1996
delay for station
has been also obtained
1998
Gilmore Creek. and submitted
to the IVS.
233
IAA Analysis Center
3.4.
Institute of Applied Astronomy of Russian Academy of Sciences (IAA)
Comparison The
basic
and
software
combination
of EOP
for comparison
of EOP
compute and investigate systematic differences in every-day use in the EOP service. Software from different
observational
techniques
series
series
is developed.
This
software
of EOP and TRF series and related for combining EOP series including
allows
us to
statistics. It is those obtained
is also advanced.
In 2000 we performed intensive study of systematic differences between EOP series and CRF realizations obtained from NEOS-A and CORE programs with OCCAM and ERA packages. It was found, in particular, that EOP results substantially depend on software and CRF used for computation. Table
The
2 presents
differences
between
some obtained
EOP
series
contain
Table 2. Wrms of differences between EOP series obtained pro 7am packages and two radio source catalogues
3.5.
Program
/ catalog
NEOS-A NEOS-A NEOS-A
/ IAA / ERA / WGRF / ERA / IAA / OCCAM
NEOS-A
/ WGRF
CORE-A CORE-A
/ IAA / ERA / WGRF / ERA
CORE-A
/ IAA
CORE-A CORE-B
systematic
components.
/ package
from different observational
with EOP(IERS)C04
using two
removing linear trend.
Xp, Iza_ 323/271 273/265
]Iv, #as 287/246 268/232
UT1, 0.1 #s 170/105 140/97
A¢, #as 570/531 550/521
A_, /zas 254/201 206/192
219/200
202/165
103/93
328 /306
142/133
103/93
328/305 142/134
219/201 202/165
/ OCCAM
before/after
programs
453/389
448/320
261/229
808 /619
325/252
398/361 213/194
343/306 247/170
238/214 114/107
737 /630 467 /420
241/228 180/174
/ WGRF / OCCAM / IAA / ERA
204/194 357/313
219/173 298/287
124/114 247/192
489 /426 763/725
188/184 268/203
CORE-B CORE-B
/ WGRF / ERA / IAA / OCCAM
374/322 273/207
317/294 250/218
270/207 158/140
764/729 545 /521
240/226 185/170
CORE-B
/ WGRF
273/208 258/225
159/141
550/526 190/176
First The
networks
/ OCCAM
results
/ OCCAM
of program
multi-functional
package
with the purpose
The package
runs
1. Flexible 2. Different
under
methods
least squares
Windows
QUASAR
QUASAR
of studying
is aimed
at processing
Earth
rotation
and improving
9x. Main
features
of the package
of parameter
observations coordinate
of global systems
VLBI
accuracy.
are:
control
or reject
Package QUASAR were processed using
estimation:
multi-parameter
least
squares
(MPLS)
(real-
least squares (MGLS) (realized); moving least squares filter (MLSF) Kalman filter (OKF) (realized); moving Kalman filter (MKF) (planned);
collocation
3. Multi-window to correct
package
parameterization.
ized); multi-group (planned); optimal
234
significant
results.
(LSC) system
outliers,
(realized). which
allows
and organize
the user input-output
to select and database
tune
the reduction
model,
control.
was applied to processing NEOS-A observations for period 1997-1998. LSC techniques. The accuracy of EOP determination in comparison
Data with
2000 IVS Annual Report
Institute
of Applied
Astronomy
EOP(IERS)C04 different
of Russian
series is presented
estimation
techniques
Academy
of Sciences
in Table 3. Comparative
Yp, mas 0.17
NEOS
Intensives
The most
Twelve
observations accurate
sessions
and estimates
carried
of intraday
• wet component good
analysis
UT1,
with the QUASAR
0.1 ms 0.09
for 1998-2000
were obtained
out during
CONT94
stochastic
troposphere
were obtained
delay WVR
Secular
for all stations
Estimates
of all stochastic
regulariza-
LSC technique
and
Onsala
to total
parameters
Gipson's
of programs
was detected;
that
of are
and secular Love l(°)=0.087+0.001,
permanent
their
is in
gradients
models
tide in the ref-
were estimated may be caused
and
result
horizontal
from 12 daily by insufficient
IRIS
(1984-1992)
autocovariance therefore
func-
further
LSC
Outlook We plan for the coming
year:
• Regular
of combined
computation
Analysis
Coordinator
• Development source
for further
of algorithms
computation
of session
• Comparison of weekly VLBI and GPS. • Beginning QUASAR
IVS
and
eops and eopi series and submission
of results
to the IVS
investigation. software
for analysis,
comparison
and combination
of radio
catalogs.
• Regular
2000
and LSC tech-
using
(for station
observations
tions were obtained. Significant instability of these functions evaluation will be carried out by use of iteration process. 4.
OKF
of global nominal h(°)--0.579+0.003,
are related
modelling of vertical motion of Earth crust. LSC technique has been also applied to processing
ma8
0.20
significant
Moreover, nominal Love and Shida numbers show some instability of local number h that
(1993-1999).
with
as follows:
measurements);
numbers
AE_
were processed
were used for determination following values were obtained:
hs=0.795+0.009,/s=0.129+0.002.
and NEOS-A
Center
obtained
with use of stochastic
wet troposphere zenith delay were found for some stations. • residual variations of PM and UT with reference to Ray's consistent within ±0.1-0.3 mas.
erence frame ITRF'97. sessions. These results
Analysis
package for 1997-1998.
using MPLS,
by MPLS
experiment
components
with independent
The same observations and Shida numbers. The
of EOP results
A¢ sine, mas 0.14
were processed
estimations
of zenith
agreement
IAA
is underway.
Table 3. Accuracy of EOP series obtained
niques. tion.
(IAA)
Annual
of regular
station
submission
station
coordinates
coordinates
and
of EOP computed
in SINEX troposphere
format. delay
from NEOS-A
solutions
and NEOS-I
obtained
sessions
from
with
package.
Report
235
Z
z ooqi *' 7 5 S S 75
¸
Italy CNR
Analysis Center
Istitutodi R_lio_tronomia-Bolo_a
Italy
CNR
Analysis
Center
Report
P. Tomasi Abstract This report summarises the work of the Italian CNR fundamental information about the structure of the center,
1.
VLBI Analysis Center. It will its locations, and its activity.
give
the
Introduction
The Italy CNR VLBI Analysis delle Ricerche (CNR) to improve European area. The two institutes
Center is the joint effort of two Institutes of Consiglio Nazionale the quality of the geodetic VLBI results, in particular in the are:
a) the Istituto di Radioastronomia (Institute of Radio Astronomy, where the main research activity is carried out, both in radioastronomy
IRA) located and geodesy;
in Bologna,
b) the Istituto di Tecnologia Informatica Spaziale (Institute of Informatica and Technology for Space, ITIS), located in Matera at the Center of Spatial Geodesy (of the Italian Space Agency), where VLBI antenna, laser ranging telescope, permanent GPS receiver and PRARE antenna are located. Also a different analysis center is located Italian Space Agency and run by Telespazio. However the two institutes "Istituto di Radioastronomia", carry
here.
All these
structures
are properties
mentioned above will become quite shortly a single with a section located in Matera. The new CNR's
on the same commitment
to IVS as the previous
of the
institute, institute
the will
two intitutes.
The IRA have started to analyze VLBI geodetic database from 1989, using CALC/SOLVE package at the HP1000 at the Medicina station. In the following years that software was installed on an HP360 workstation and later on on an HP715/50 workstation. We have analyzed here mostly
databases
with some
European
baselines,
generally
at least
three.
Most of the databases
have been reprocessed here in Bologna (using CALC and SOLVE). We are now using CALC9.1 and the November 2000 version of f-solve, for data analysis. We will soon move to the updated version of f-solve (February 2001). From 1997 also ITIS have installed the CALC/SOLVE specialized the Bologna section to analyze single databases, The global solutions but with a previous 2.
Data
Analysis
In Bologna
have been computed version with respect and
and after some tests we have to produce the final database.
in Matera at the ITIS. In Matera to the one installed in Bologna.
we are also using f-solve
Results
the main computer
is HP715/80;
we are now analysing Matera computer. We are continuing
single experiments
in order
the repeatability
to improve
software in order
the computer
(interactive
to work on the possibility of the
name
solve); the global
of using tropospheric VLBI
geodetic
results.
is boira6.ira.bo.cnr.it. solutions zenith
path
We have
On it
are run mostly
on
delay from GPS inserted
the
wet
zenith path delay in the VLBI database as if this information was derived using a water vapour radiometer. The tropospheric data have been collected at the Berna site of the IGS. However the IGS data, with an hour interval, are the total tropospheric delay. For that we have subtracted
236
2000
IVS
Annum
Report
Istituto diRadioastronomia-Bologna
the dry delay,
from the VLBI
data,
Italy CNR Analysis Center
in order
been inserted into the VLBI database using the Niell mapping function was implemented have been corrected. In Matera
the
main
computer
to produce
the
"wet"
zenith
delay.
These
data
have
an updated version of DBCAL. In this new version and also some other errors present in the program
is an HP282
computer
with internet
name
hp-j.itis.mt.cnr.it.
Also here we have installed f-solve (the center name is ITISCNR) and we are using it mostly global solutions in order to compute the positions and velocities of European stations.
for
The use of GPS tropospheric zenith path delay have produced some interesting results. On the European database of 1998, the use of the new way of analysing VLBI data seems to produce a better repeatability on the European baseline length (Rioja at al. 2000). 3.
References M. J. Rioja,
P.
Tomasi,
ments into the VLBI analysis of the 14th Working Meeting editors, IRACNR 2000.
2000 IVS Annual Report
P. Sarti,
M.A.
Tortes
Integrating
GPS
zenith
path-delay
measure-
of geodetic observations with the European Network. - Proceedings on European VLBI for Geodesy and Astrometry. P. Tomasi et al.
237
.' ; _.///
.:(it,, d. !
_'7
_ -_
/
IGG Analysis
Center
Vienna
Institute
IGG
Special Harald
of Geodesy
Analysis
Schuh,
and Geophysics
Center
Johannes
B6hm,
/ University
Annual
Thomas
of Technology,
Report
Vienna
2000
Hobiger
Abstract A short overview about the Institute of Geodesy and Geophysics (IGG) at the Vienna University of Technology is given and its activities as IVS Special Analysis Center are described. Topics currently worked on and future plans are described.
1.
Introduction The
Institute
Austria, since
of Geodesy
was officially 1999
the
VLBI
OCCAM
and
on
2.
at
IGG
Staff
Personnel (Head location
3.
100%)
and
Modification Together
the
• Modeling Based ents
test,
constraints
and
of St.
in Vienna
assistants
package
axe Harald
Johannes
the
of the
Schuh
BShm
et al.,
University)
Munich) OCCAM
a group
for
the
and was
software.
Gauss-Markov
functions
(BShm
Petersburg
DGFI,
enhance
linear
used
for the
of gradients.
The
one
of good
results
estimation
VLBI.
SOLVE
and
in Figure
software
delays.
(al-
model
clocks,
the
At
Volker
set
up
IGG,
in OCCAM
zenith
path
in we by
delays
2000).
refraction
tion shown
further approach
least-squares
and
example
and
gradients
by GPS
were
Already
OCCAM Institute
of piecewise
classical
(OCCAM
in Vienna,
4, 2000.
Center
Center
research
Forschungsinstitut
least-squares
tropospheric
the
package
(Astronomical
develop
classical
determined
applied
procedure
Different
for VLBI, piecewise
linear
axe described
agreement
software
BERNESE
packages and
functions in BShm
between
we compared GIPSY to check
et ai.
gradients
for the
two
for GPS). their
(2000)
derived
tropospheric techniques Moreover
impact and
by
on the
BShm
GIPSY
gradi-
and
et al.
were several estima(2001)
OCCAM
is
1.
Outlook During •
Further datum
238
Titov
of tropospheric on
the
VLBI path
Analysis
Analysis
and
of the
of tropospheric
Special
Special
of Technology
on December
(50%).
software
estimation
horizontal
IVS
Geodesy)
Geod/_tisches
to
University Center
modification
modeling
IVS
the
IGG
VLBI
Oleg
the
allowing
the
Hobiger
at
2000
extended
4.
Thomas
(Deutsches
summer
with
at
Analysis
on the
the
the
of Advanced
of the
worked
with
associated
with
Tesmer
has
(IGG) Special
concerning
associated
Analyses
and
at IGG
Department
Special •
group
Geophysics as an IVS
investigations
at IGG
of the
and
appointed
the
year
2001
development
the
plans
of the
of OCCAM,
IVS
e.g.
the
Special
Analysis
implementation
Center
at IGG
of a free network
include: solution
and
its
definition.
2000 IVS Annual
Report
Institute
of Geodesy
and Geophysics
•
Contributions
•
Research
on
functions
and
•
to new
•
working
tropospheric
of
group
models
tropospheric
IRIS-S
Contributions for
IVS
of Technology,
on
Vienna
IGG
geophysical
which
Analysis
Center
models.
correspond
to
the
traditional
usage
of
mapping
gradients.
Comparisons NEOS-A,
the
/ University
to
parameters
and
EUROPE
special
IVS
derived
by
VLBI,
GPS
and
WVR
data
based
on
EOP
estimates
sessions. projects,
e.g.
the
pilot
project
2000
by
delivering
12
1=5
ll8
211
24
ll2
lj5
lj8
211
24
1999.
_0
-2 -3 0
31
I
I
6
9
3 2
-2 -3
Figure
1.
1999
and
interval
was
as markers Space
and
chosen for GPS
Observatory,
for this
2000
North simultaneous
east GPS
and
the
(GIPSY), Chalmers
I
l
I
3
6
9
gradients
at
measurements. constraints circles University
Wettzell For for the
for VLBI
station the
gradients (OCCAM).
of Technology,
for
estimation
the
VLBI
session
of tropospheric
were
set
to
0.6
mm/sqrt(h).
Acknowledgement: Sweden,
provided
IRIS-S parameters
Ruediger the
gradients
136
on
15
March
a 3 hours' Diamonds Haas obtained
time
are from by
used
Onsala GIPSY
comparison.
IVS Annual
Report
239
IGG
5.
Analysis
Center
Institute
of Geodesy
and
Geophysics
/ University
of Technology,
Vienna
References
BShm, J., R. Haas, H. Schuh GPS and VLBI. Proceedings Astrometry,
Bologna,
and R. Weber: Comparison of tropospheric of the 14th Working Meeting on European
September
2000, ed.
by P. Tomasi,
F. Mantovani
gradients determined VLBI for Geodesy
by and
and M. A. Perez-Torres,
pp. 41-46, 2000. BShm,
J., H. Schuh
and VLBI. Schuh,
and
Submitted
R. Weber:
to 'Physics
Comparison
and
H., and H. Schmitz-Huebsch:
Geophysics Tesmer,
(in press),
Comparison
of the 14th Working
Meeting
September
2000, ed. by P. Tomasi,
Titov,
and
O.,
H. Schuh:
least-squares collocation tions in Earth Rotation',
Short
of the Earth',
periods
in Earth
gradients
determined
by GPS
2001.
rotation
as seen by VLBI.
Surveys
in
2001.
V., and H. Schuh:
ceedings
Chemistry
of tropospheric
Short
of the Results on European
F. Mantovani periods
in Earth
Obtained VLBI
by Different
for Geodesy
and
and M. A. Perez-Torres, rotation
seen in VLBI
VLBI
Networks.
Astrometry,
Pro-
Bologna,
pp. 7-12, 2000. data
analysed
by the
method. IERS Technical Note 28, 'High frequency to subseasonai variaObservatoire de Paris, ed. by B. Kolaczek, H. Schuh and D. Gambis, pp.
33-41, 2000.
240
2000
IVS Annual
Report
2oozoo Observatoire deParis,DANOF/UMR 8630 Paris
Observatory
A.-M.
Paris
Analysis Center OPAR: March 1999 - December
Gontier,
M. Feissel,
N. Essai_/,
Observatory
Analysis
Report 2000
D. Jean-Alexis,
on
Center
(OPAR)
Activities,
K. Le Bail
Abstract The
1.
OPAR
time
stability
was
continued.
Analysis
Center
of the celestial The
team
activities
reference was
not
over
frame.
changed,
March The
except
1999
routine
- December analysis
for the
help
2000
focused
of the intensive of one student
on analyses and
24-hour
(six months
of the sessions
in 2000).
Activities
1.1.
Stability The
of ICRF
capability
of the
VLBI
geodetic
and
astrometric
programs
to maintain
stable
directions
in space was evaluated [1] on the basis of time series of session-per-session source coordinates computed at USNO using the CALC-SOLVE software [2]. The systematic and random characteristics of several hundreds of source apparent motions were investigated in order to derive a set of qualifiers that would be helpful in selecting sources to maintain a precise and stable celestial reference frame. We developed a selection process based on the density of observations over 1987-1999 and on the time stability of averaged yearly coordinates. The stability considered is that along the maximum variability direction in a source-fixed frame. 242 sources were thus selected. The rotation reference frames are shown on Figure 1. The results of this selection ing", "candidate" and "other" comments can be made. .
ICRF
categories.
angles
of the
corresponding
differential
celestial
process are compared to the current ICRF qualifiers [3], i.e. "definsources, and structure index, is shown in Table 1. The following
The stability
test keeps
practically
all "defining"
and
"candidate"
sources
that were preselected on the basis of their observational history, and most of the "others". When considering the complete ICRF-Ext.1, one can note first that only 1/3 of the "candidate" sources were selected on the basis of long and dense observational history. In fact we know that a number of "candidate" sources axe considered so because their time span of observation
is still too short.
We also know
that
a number
of sources
were qualified
as
"other" although they had a dense observational history, explaining the selection of 3/4 of them. The selection rate of the "defining" sources is between the other two (1/2). Already at this first level, the first part
of our selection
scheme
(based
on the observational
history
of
the source) provides a pre-qualification of sources which is quite different from the current ICRF one. Once this first selection is performed, the second one, based on the internal consistency of the time series of coordinates in the direction of the maximum variability, keeps nearly
all "defining"
and
"candidate"
sources,
thus
confirming
their
current
ICRF
status.
Meanwhile, 7/10 of the "other" sources are still kept. This seems to indicate that using time series information might bring in more sources that would contribute to stabilize the celestial reference frame.
2000
IVS
Annual
Report
241
Paris Observatory
Analysis
Center
(OPAR)
Observatoire
0.6
de Paris,
DANOF/UMR
8630
0.6 dA1 (mas)
0.3
0.3
0.0
0.0
-0.3
-0.3
-0.6
-0.6 1988
1992
1996
2000
1988
1992
1996
2000
dA3 (mas)
0.3 0.0 -0.3 36
-0.6
72
Figure
l. Rotation
angles
on the basis
of dense
coordinates
were available
to the stated
Table
1. Match
the basis
of 12 yearly
observational
differential
observation
are listed
the ICRF
then
a percentage % All
stable
242 sources
The numbers
The double
selected
of sources
horizontal
qualifiers.
of them %
sources
The
sources
is recognized
are first
selected
as stable. Number
stable
stable
2. Structure
index
212
49%
1
49
86%
Candidates
98
88%
294
29%
2
87
80%
Other
73
67%
102
48%
3
63
87%
4
26
85%
structure
from
the
index
for each
irregularity The
of the lack
source
source
[4] qualifies
emission
of correlation
study
not only but
also
also
to enhance
properties
or for realistic
highlights
for internal of the
studies
the
between
usefulness
purposes the
support
non-rigid
of source
such
this
structure
of position
index
and
observational effect.
ICRF
quality
to scientific
through
level
(1 for the
of considering
as the
of VLBI
Earth
the
structure
analysis
or microlensing
the
and
time
disturbance
less disturbed,
our
stability
errors
to other
of radiosource
direc-
like differential
as in the understanding
of precession
and
most
suggests
due
or applications
research,
expected
4 for the criterion
analysis
evolution
control
nutation
of the
observations,
effects.
In another study [5], using a set of 16 well observed radio sources (north of +20 degrees), was shown that reliable information can be obtained on the local motions in the sources since end
242
of the
1980's,
with
a 0.5-year
time
resolution.
The
on
%
presel,
95%
The
whose
line corresponds
108
This
physical
one, using
#as).
source
that, for the data set used in this study, the factors tend to dominate the source structure
VLBI,
graph).
(+20
with
to a mean
over 1987-1999.
(dA3
history, Number
2000
categories
disturbed).
tions,
138
relative
stability
selection
Defining
.
CRFs
axes directions
presel, 1. ICRF
191
1996
and time
year
of the ICRF
of the source
of a dense
135
1992
history
in a given
uncertainty
87
i
1988
analysis
showed
that
the
variability
2000 IVS Annual
it the of
Report
Observatoire
de Paris,
DANOF/UMR
8630
Paris
these objects have varied spectral characteristics, processes taking place in the sources.
1.2.
OPAR
time
Computation
series
of source
of time series of source
standard deviations of the are 0.13 mas in R.A.cos(Dec)
could possibly
Analysis
be related
Center
to diverse
(OPAR)
physical
coordinates coordinates
inary results were obtained for 52 sources 37 of them, for which the 1998 coordinates weighted analyses
that
Observatory
referred
to the ICRF
was initiated.
over 1999. Figure 2 shows the average could also be derived from the USNO
yearly position differences between and 0.18 mas in Declination.
the
Prelim-
coordinates of [2] series. The
USNO
and
OPAR
1.0 CD
E
J
0.5
g oo 0
_
_
•
o_ -0.5 P .< -1.0
!
O
rr
'_ E
0.5
!
O
=
• t 0
0.0 C O
i
•
o q o,_ ¢.
L0
-0.5
;%°
_**,:.#" o o
•
'A ,o_. .
0
¢
t'-
-1.0 D
Declinations
-1.5 -40 Figure
2.
Average
-20
coordinates
0 for
37
20
common
sources:
40 USNO
(degrees)
60 1998
80
(brown/light)
and
OPAR
1999
(blue/heavy)
1.3.
Operational
analyses
The analysis
of the intensive
sions was initiated.
Results
one-baseline
were provided
sessions to IERS
was continued and IVS.
and
The results
that
of the 24-hour
obtained
ses-
are illustrated
in Figure 3. The standard deviation of the differences of the OPAR solutions with the IERS series C04 over 1999 is +20 #s on UT1-UTC for the intensive sessions; for the 24-hour sessions: +0.28 mas on polar motion, +12 #s on UT1-UTC and =t=0.22 mas on celestial pole offsets.
2.
Prospects
Our plan is to continue developing reference frame studies and applications. studies will contribute to the work of the IERS ICRS Product Center, with which
2000
IVS
Annual
Report
Most of these the OPAR IVS
243
Paris Observatory
Analysis
1
Center
(OPAR)
Observatoire
de Paris,
DANOF/UMR
8630
dX pole (mas)
0 -1
Date (years)
1
dUT1, 24-hr (mas)
0 T 4
*
•
f Jt
-1
Date {years} ,
!
dPsi*sin(Eps)
0.3
(mas)
0.0 -0.3
Date (years) I
1999.0 Figure
Analysis
center
1. Time
I
1999.5 3. OPAR
is closely
2. Global 3. Time
results
coordinates
and operational
apparent motions, the IVS observing sessions, available
EOP
Difference
with
EOP(IERS)
C04.
to the ICRF.
applications,
website
reference
series of terrestrial
referred
e.g.
These
time series can be used in sev-
the astrophysical
interpretation
of observed
accurate use of the sources in differential VLBI, the scheduling of the optimization of future revisions of ICRF. The time series will be
on the ICRS-PC celestial
in 1999.
associated.
series of source
eral research
2000.0
frame
(http://hpiers.obspm.fr/icrs-pc).
analyses.
reference
frames.
References [1] A.-M. Gontier, K. Le Bail, M. Feissel, frame. AA (in press) [2] T.M.
Eubanks.
[3] International [4] A.L.
Earth
A.-M.
2001. Stability
of the extragalactic
VLBI
reference
communication
Rotation
Fey, P. Charlot,
[5] M. Feissel,
244
Private
T. M. Eubanks,
2000,
Gontier,
Service ApJS, T.M.
(IERS),
1999,
1998 Annual
Report,
83. Observatoire
de Paris.
128, 17 Eubanks,
2000,
AA, 359, RN1201
2000 IVS Annual Report
9 5>, ,,;;' Lt Onsala
Space
Observatory
The
(OSO)
IVS
Onsala
Special
Analysis
Center
Space
at
Observatory
the
(OSO)
Onsala
Analysis
Center
Space
Observatory Riidiger
Haas, Hans-Georg Scherneck, Lubomir P. Gradinarsky, Boris
Gunnar Stoew,
Elgered, and Sten
Jan M. Johansson, Bergstrand
Abstract We give a short Current
deformation
in Europe,
scopes, scribed.
1.
overview
Observatory.
combining
topics
and
on the
activities
of analysis
atmospheric integrating
IVS
radio VLBI
wave
Special
are ocean
propagation,
and
GPS
and
Analysis tide
and
thermal earth
Center
at the
atmospheric
deformation
rotation.
Onsala
loading, of VLBI
Future
plans
are
Space crustal
radio
tele-
briefly
de-
Introduction The
IVS Special
Analysis
Center
at the
number of particular problems which and analysis programs, and providing data 2.
of the
and research
in a service Ocean
sense is performed
Tide
The studies tide loading
Onsala
Space
Observatory
(OSO)
concentrates
on a
can be investigated using and developing VLBI databases ancillary parameters. No routine analysis of global VLBI
or planned
at OSO
for the next few years.
Loading
performed
effects.
at OSO cover theoretical
New ocean
tide loading
modelling
coefficients
been calculated and made available for a global site http://www.oso.chalmers.se/_hgs/README.html
and empirical
based
on recent
determination ocean
tide
of ocean models
have
set of VLBI stations [1]. The ocean loading includes loading parameters computed
web on
the basis of the recent GOT99.2 tide model [2]. A case study for the IVS station Westford showed that the refinement of the tidal modelling at the continental shelves leads to an improved agreement between modelled ocean tide loading and three-dimensional ocean tide loading effects derived from the analysis of VLBI data [1].
3.
Atmospheric
Loading
A data base with time series of atmospheric loading predictions based on global pressure fields has been generated for most of the VLBI databases since 1990 [1] and is available from our http server 4.
ht t p: //www.oso.chalmers.se/,-_hgs/apload/apload.html.
Crustal
Deformation
The pure geodetic
European
in Europe VLBI experiments
observed
ing the two-step analysis strategy described in [3]. Crustal large-scale strain-rate field in Europe have been determined
2000
IVS
Annual
Report
since 1990 have been motion [4].
results
analysed
apply-
and the corresponding
245
Onsala Space Observatory 5.
(OSO)
Atmospheric Atmospheric
Radio studies
microwave radiometry 1993 to 1998 showed
Analysis
Wave have
Center
Space
Observatory
(OSO)
Propagation
been
at Onsala correlation
Onsala
performed
using
the
collocated
techniques
VLBI,
GPS
and
[5]. Simultaneous observations with these three techniques during coefficients for the zenith wet delay between 0.74 and 0.87 and
for the horizontal delay gradients between 0.27 and 0.51 [6]. Equivalent zenith wet delay values derived from VLBI and GPS have also been compared to values from Numerical Weather Prediction (NWP) models [7]. The agreement is promising with correlations at the level of 0.8.
6.
Thermal
Deformation
of VLBI
Radio
Telescopes
The simple model describing the deformation of radio telescopes due to thermal influences [8] has been used to model the effects and to compare them to the vertical height changes measured at Onsala and Wettzell with the respective invar measurement devices (see Fig. 1).
Onsala
Wettzell ®
oE_I
®
®
¢-
®
-_ -2
®
> ¢-3
a 1996
1997
Figure
1. Vertical
by
invar
the
temperature
7.
rod from
Combining
1998
height
1999
chmlges
measuring the
of the
systems;
VLBI
and
2000
data
base,
Integrating
2001
VLBI stars
1997
radio
telescopes
in circles
thermal
VLBI
at Onsala
- modelled
expansion
and
with
coefficient,
1998
and
Wettzell:
a simple and
1999
the
solid
model
based
telescope
2000
lines on
2001
- measured daily
mean
dimensions.
GPS
Since each space geodetic technique has specific advantages and disadvantages, the combined and integrated use of several space geodetic techniques seems to be a useful approach. This is especially true for investigations concerning the crustal strain-rate fields and for the determination of absolute VLBI and
sea level changes. Therefore we started first investigations to combine and integrate GPS in Europe [9]. The continuously growing data set of daily GPS solutions since
1993 available at OSO and in particular the GPS excellent basis to continue these investigations.
246
data
from the BIFROST
project
2000
[10] offer an
IVS Annual
Report
Onsala Space Observatory (OSO)Analysis Center
Onsala Space Observatory (OSO) 8.
Earth
Rotation
The IVS Special Analysis Center at the Onsala Space Observatory IVS Analysis Pilot Project and submitted an earth orientation parameter from the 52 NEOS-A
sessions
participated in the First (EOP) solution obtained
in 1999 (see Fig. 2).
300 I
15 ITV,TrETT[ITiTITWCTI,TTjwTItTI]!,TI,TI$It 400 o,.350 >- 300 250
,.300 f >- 150i-
o iTT.T[]TTTIITTT, TIjT,TIETITITT, TT,!LTTITITT, TT.TI,TTITTI[T=TT +
L
ID 150 "O 300 II ,.. 0 T:TItTTTIItTI,TTJLTT.TTTIITT, TTJT,TTtTITT, TT,IT,TTITTTIt_IT,
_-50
rI
-45
TllIli]1111i.Tl.l]:lj.TT]iIl+'j'[,
._ -50 -55
-o
0 -5 -10
,
,
,
J
Figure 1999 in
2. for
=
F
M
OSO's the
First
milliarcseconds,
UT1-UTC
9.
_ 30011 150 0 IITT]TTTITIt tTTJ[JT3 TTItTT, TT,T LTTIT_T[TT:TT,T[ITTTITZII: J F M A M J J A S O N D
,
(dUT1)
A
M
J
submission IVS the an
J
right
S
of earth
Analysis
offset,
A
O
D
orientation
Pilot
parameters
Project.
column a drift,
N
shows an
The the
annual
left
derived column
respective and
from shows
standard
a semi-annual
the the
52 NEOS-A earth
deviations term
are
experiments
orientation in
in
parameters
microarcseconds.
For
subtracted.
Outlook
The TVS Special Analysis Center at the Onsala Space Observatory will continue to work on crustal loading and deformation effects. Special focus will be ocean tide loading and atmospheric loading but we will also work in the field of solid Earth tides. Parameter estimation and the covariances with EOP determinations will be of main interest. Eventually we will also contribute to IVS by submitting EOP solutions. We will continue to analyze the European VLBI data with the aim to derive the most robust and reliable results for crustal motion and strain-rates. Our investigations will include also combination strategies with other space geodetic techniques like GPS, especially to achieve a more detailed view on the strain-rate field in Europe and to investigate changes in absolute sea level. We will also work on the geophysical interpretation of the results. Our research concerning atmospheric properties will continue collocated
space geodetic
and remote
sensing
techniques
The investigations will reach from small scale structures with the new microwave radiometer [11] to climatological
2000
IVS
Annual
Report
available
and
we will use especially
at the Onsala
in the atmosphere studies.
the
Space Observatory. that
can be detected
247
J fl
f
Onsala Space Observatory
(OSO) Analysis
Onsala
Center
Space Observatory
(OSO)
References [1] Scherneck, H.-G., R. Haas, and A. Laudati, Ocean 2000 General Meeting Proceedings, N. R. Vandenberg 257 262, 2000. [2] Ray, R., Global 209478, 1999.
Ocean
Tide Model
[3] Haas, R., and A. Nothnagel, Interferometry (VLBI) data, and Astrometry, W. Schl/iter
Loading Tides For, In, and From VLBI, In: and K. D. Baver (eds.), NASA/CP-2000-209893,
From TOPEX/POSEIDON
Altimetry:
GOT99.2,
A two-step approach to analyze European geodetic In: Proc. of the 13th Working Meeting on European and H. Hase (eds.), 108-114, 1999.
IVS
NASA/TM-1999-
Very Long Baseline VLBI for Geodesy
[4] Haas, R., E. Gueguen, H.-G. Scherneck, A. Nothnagel, and J. Campbell, Crustal motion results derived from observations in the European geodetic VLBI network, Earth, Planets and Space, 52, 759-764, 2000. [5] Gradinarsky, L. P., R. Haas, G. Elgered, inferred from microwave radiometer, GPS 698, 2000.
and J. M. Johansson, and VLBI observations,
Wet path delay Earth, Planets
and delay gradients and Space, 52, 695-
[6] Haas, R., L. P. Gradinarsky, G. Elgered, and J. M. Johansson, Atmospheric parameters derived from simultaneous observations with space geodetic and remote sensing techniques at the Onsala Space Observatory, In: IVS 2000 General Meeting Proceedings, N. R. Vandenberg and K. D. Bayer (eds.), NASA/CP-2000-209893,
269
273, 2000.
[7] Behrend, D., L. Cucurull, J. Vii/t, delays using VLBI, GPS and NWP
and R. Haas, An inter-comparison study to estimate models, Earth, Planets and Space, 52,691-694, 2000.
[8] Haas, R., A. Nothnagel, H. Schuh, and O. Titov, Explanatory Deformation" of the IERS Conventions (1996), DGFI Report
Supplement 71, H. Schuh
zenith
wet
to the Section "Antenna (ed.), 26-29, 1999.
[9] Scherneck, H.-G., J. M. Johansson, and R. Haas, BIFROST Project: Studies of Variations of Absolute Sea Level in Conjunction With the Postglacial Rebound of Fennoscandia, In: R. Rummel, H. Drewes, W. Bosch, H. Hornik (eds.), Towards an Integrated Global Geodetic Observing System (IGGOS), IAG Symposia (120), International Association for Geodesy, 241 244, Springer-Verlag, Berlin, 2000. [10] Johansson, J. M., J. L. Davis, H.-G. Scherneck, G. A. Milne, M. Vermeer, J. X. Mitrovica, R. A. Bennett, B. Jonsson, G. Elgered, P. E16segui, H. Koivula, M. Poutanen, R. O. RSnn/_g, and I. I. Shapiro, Continuous GPS measurements of postglacial adjustment in Fennoscandia, 1. Geodetic results, Journal of Geophysical Research, submitted 2000. [11] Stoew, B., C. Rieck, and G. Elgered, First results from a new dual-channel water vapor In: Proc. of the 14th Working Meeting on European VLBI for Geodesy and Astrometry, F. Mantovani and M.-A. Perez-Torres (eds.), 79-82, 2000.
248
radiometer, P. Tomasi,
2000 IVS Annual
Report
/
2 oo 2c c
--
i3. ' SHAO,
NAO,
Chinese
Analysis
Academy
Center
of Sciences
Report
Shanghai
from for
Shanghai
Astronomical
Observatory
Astronomical
Analysis
Center
Observatory
1999.03--2000.12
Jinling
Li, Guangli
i'l,hng
Abstract Here
we summarize
nomical Observatory in the coordination and
several
geodetic thanks
1.
Chinese
application
the
activities
national studies
geodetic of VLBI.
to all IVS colleagues
Observation
of the
astrometric
during the period from of the VLBI observations
and
others
and
projects,
the
data
We also describe giving
geodetic
March 1999 to the for Asia-Pacific
archives
our plans
VLBI
group
of Shanghai
Astro-
end of 2000. Our activities are involved Space Geodynamics (APSG) program and for the
reduction, year
the
2001 and
astrometric
and
finally
our
show
us help.
Coordination
Outstanding characteristics such as high precision repeatability for long baseline surements and providing high precision observations in the quasi-inertial deep space make VLBI one of the key supporting program and several Chinese national
techniques of the Asia-Pacific geodetic projects, for instance,
work of Crustal Movement, the Mechanism hi January and October of 2000, our group experiments. The antennas ber of 1999 two international
length meabackground,
Space Geodynamics (APSG) the Chinese Observation Net-
and Prediction of Continental organized in total four 24-hour
Intensive Earthquakes. Chinese national VLBI
are one fixed at Sheshan and one 3-m mobile at Kumning. In NovemVLBI sessions were coordinated and in October of 2000 one session.
All are for the APSG program. The stations are Sheshan and Urumqi of China, Gilereek and Kokee of USA, Kashima of Japan and Hobart of Australia. These observations are important to the studies of contemporary crustal motions within the China mainland as well as in the Asia-Pacific region. 2.
Data
Archives
and
Reduction
The original HP C180 workstation was updated by extending the memory capacity to 260 Mb and the hard disk to 54 Gb. The originally installed CALC8.2 was replaced by CALC9.1. The observations were archived in personal computer disk, which is cheaper, faster and more convenient than
originally used 4-ram tape and its tape driver. As a milestone in our group's history of data reduction,
Mark
III VLBI
observations
August 1979 and December 1998 were successfully analyzed in 1999. It was the our group to perform a full time span global VLBI data reduction. We compared with ITRF96, RSC (WGRF) 95 R01 and EOP (IERS) 97 C04. The three orientation the Celestial Reference Frame are not significant at the level of precision of O.lmas.
between
first time for our solution angles Though
for no
significant values are found for the three deformation parameters, coordinate drifts up to 0.5mas are identifiable for some sources in the southern hemisphere. The relative rotation angles and their rates of change for the Terrestrial Reference Frame are not significant respectively at the precision level of 0.2mas and O.lmas/yr. Detailed comparisons velocity field are obvious for the eastern part of Eurasian
2000
IVS
Annual
Report
however show that the differences plate and Australian plate. About
in the Earth
249
Shanghai Astronomical Orientation
Observatory
Parameter
Analysis
series,
Center
the systematic
SHAO,
differences
respectively at the level of 0.4mas and 0.1mas/yr. In the year 2000, our global VLBI solution was adopted
NAO,
Chinese
and the relative
drifts
as one of the three
latest version International Terrestrial Reference Frame (ITRF2000), to the whole group and also to the supervisors of our work unit. 3.
Application
3.1.
of Sciences
are not significant
input
solutions
of the
is really encouragement
Studies
Temporary Based
which
Academy
crustal
on our global
movement
VLBI
solution,
we analyzed
the motion
of Sheshan
VLBI
station
using
two different methods. One is based on the prediction of plate motion model. The other is based on the absolute angular velocity of plate. In the first method, the VLBI measurement of Eurasia plate motion was compared following equation,
vy
with the prediction
-
Vz
vy
NNR-NUVEL1,4
=
Vz
VLBI
of the plate
T2
+
motion
-Ra R2
T3
model
D
NNR-Nuvella
R1
y
D
z
-R1
where D, T1,2,3 and R1,2,a are respectively the scaling factor, the translation ters between tile measurement and prediction. These parameters are solved
by the
(1) VLBI
and rotation paramefor by a least-squares
adjustment in a re-processing procedure. Only stations with post-fit residuals in horizontal velocity less than the analysis formal error (la) were finally used to contribute to the solution. Then after the removal of the effects of systematic transformation parameters and the prediction of plate motion
model
from
the VLBI
measurement,
the motion
of Sheshan
station
relative
to the stable
part
of Eurasia plate is found to be 8.4 ± 0.4mm/yr in the direction N122.4 ± 2.8°E. In the second method, the absolute angular velocity of Eurasia plate, _(f_, ft w gt_). was solved for from the following equation,
= fix
(2)
where g and _'are the geocentric velocity and position of a station from VLBI measurement. Again, only stations with post-fit residuals in horizontal velocities less than the analysis formal error were used to solve Eurasia plate
for the absolute angular velocity. The motion of Sheshan station relative to the was found in this way to be 7.4 ± 0.3Inm/yr in the direction Nl17.4 ± 2.0°E. By
comparing this with that from the first method, the difference between them is obvious. However, if we neglect the effect of the sealing factor and the translation parameters in Eq.(1), the motion will be 7.3 ± 0.4mm/yr in the direction Nl13.5 ± 3.0°E, which becomes consistent with that from the second method within the error budgets. Since D, T and R are independent parameters from each other and modeling possible real systematic effects, the motion determined from the first method should be more reliable than from the second one. In Table
1 some results
mined by various is eastward about be to improve
250
about
the motion
of Sheshan
station
relative
to the Eurasia
plate deter-
authors are shown for eomt)arison. From this one can only say that the motion 1 cm/yr. An efficient way to improve the precision of this determination would
the temporal
coverage
of data
rather
than
solely the accumulation
2000
of observations.
IVS Annual
Report
SHAO, NAO, Chinese Academy of Sciences
Table
1. The motion
Shanghai Astronomical Observatory Analysis Center
of Sheshan
station
Author
to Eurasia Rate
Azimuth
VLBI
mm/yr 11.1+1.2
N°E 112.1+6.2
Molnar & Gipson, 1996 Zhu Wenyao et al., 1997
VLBI GPS
8.0+0.5 11.2
116.5+4.1 75.7
Zhu Wenyao et al., 1999 Yu & Kuo, 1999
GPS GPS
10.8
87.3
This paper This paper
VLBI VLBI
11.2=t=1.0 7.4+0.3 8.4+-0.4
112.3+6.4 117.4+-2.0 122.4+-2.8
1996
Tile relative solution.
(based (based motion
on absolutely angular motion) oil plate motion model) between
In Table
Eurasia
2 several
and North
determinations
America are
was also analyzed
listed
geophysical
records.
The positions
given by various authors are obviously of observations nmst be improved. Table 2. Angular Author
Technique
of the rotational
different
motion between Latitude °N 62.4 71.2 78.5 68.1 74.3 74.34
based
for coinparison.
provided generally consistent results. The rotational velocity is about faster rotation for the inodern space technique determination compared years'
plate
Technique
Heki,
VLBI
relative
authors
0.2°/Myr with a slightly with the past millions of
pole and the azinmths
from each other,
on our global
Various
so again
of major
the (:overage
semiaxis
and amount
Eurasia and North America plates Pole error ellipse Angular velocity Longitude w o,,_x amin A °E °/Myr ° ° N°E 135.8 0.21 -t-0.01 4.1 1.3 -11 132.0 122.0 0.23 -t-0.03 4.1 2.4 -8 126.6 0.24 :k0.02 3.2 2.0 -30 123.0 0.231+0.008 1.8 1.4 16 137.98 0.242+0.007 3.5 2.1 -9
DeMets et al., 1994 NUVEL1A Cook et al., 1986 Earthquake Argus & Heflin, 1995 GPS Larson et al., 1997 GPS Kogan et al, 2000 GPS This paper VLBI ca: rotational velocity. a ......... cr,,,i,_: major and minor semiaxes of the lcr error ellipse. A: azimuth of major selniaxis re(:koned clockwise from north. 3.2.
Polar
motion
In a spectrum aim wavelet analysis of the VLBI determined polar motion series for the time span from August 1979 to December 1998, it is shown that (1) during the VLBI data span the Markowitz wobble does not appear, (2) the amplitudes of both variations, with the former being more obvious than
annual and Chandler wobble show temporal the latter within the observation period, (3)
all the signals in polar motion series are characterized by temporal variation in amplitudes, which means that it is ahnost impossible to separate signals by a least-squares fit and (4) by applying a low-pass
filter
the secular
polar
motion
is tbund
longitude, which is smaller in rate and more westward from optical observations (Li & Wang, 2000). 3.3.
Optical
to be 2.74+-0.01 in direction
mas/yr
compared
towards
83.9+0.3
°W
with those determined
astrometry
hnage restoration a.s in the reduction 2000 IVS Annual Report
has been shown to be a very useflfl tool for many of Hubble Space Telescope images, gamma ray data
kinds of research, and in monitoring
such the 251
Shanghai Astronomical Observatory Analysis Center
SHAO, NAO, Chinese Academy of Sciences
gravitational lenses of AGNs. Members of our group used image restoration to remove the influence of tracking error in a_strometric CCD images. As shown in Fig.l, (a) is the two-dimensional Gaussian distribution of an ideal image, (b) is the image of the standard star degraded by tracking error in a CCD frame, ((:) shows the blended images of two nearby stars and (d) shows that the image restoration the two nearby stars are well separated. By applying image restoration, precision of the center of star image can be improved, tile images of nearby 2001). The optical counterparts of 23 extragalactic radio sources, of which hemisphere, errors 4.
are observed
in right ascension
Plans
for
Most important,
the
with and
Year
CCD.
The
declination
positions
better
have
than
been
with
mean
standard
(Tang et al., 2000).
2001
....'"
try our best to provide
analysis
products
to
IVS data center quarterly. Continuously coordinate VLBI experiments for Chinese national geodetic projects and for tile APSG progranL Make some analysis various constraints on the global solution.
of the effects of Precisely deter-
mine the positions of the optical counterparts of two dozen extragalactic radio sources. Improve our ability in VLBI data reduction and application studies.
Acknowledgements
stars too (Tang et al., 13 are ill the southern
determined
0.2 arcsec
after the
We are thankful
to Drs.
all ()tiler IVS colleagues who have been giving I)y Chinese national projects (No. 95-13-03-02, F(mndation Committee (No. 19833030), and Technology Foundation of Shanghai
Chopo
_ _..._.... '°._.;_:. i
"_
_'i _ 7i_ -.,,,i.... ' :
Q_
_' ".... ' : Figure 1. Separating nearby images degraded by tracking error with image restoration.
Ma, Nancy
Vandenberg,
Axel Nothnagel
and
us help to our work. Our work ha_s been supported No. 970231003 ), Chinese National Natural Science
Chinese Academy of Sciences City (No. JC14012).
(No. KJ951-1-304),
Science
References [1] Heki K. J Geophys. Res, 1996, 101(B2): 3187--3198 [21 Molnar P, Gipson J M..!
Geophys Res, 1996, 101(B1): 545
[3] Zhu Wenyao, Cheng Zhongyi, Jiang Guojun. [4] Zhu _nyao,
/it Progress
553
in Astronomy,
1997, 15(4): 373
Cheng Zhongyi, Wang Xiaoya et al.. Chinese Science Bulltin,
[5] Yu S, Kuo L. Geophys Res Let, 1999, 26(7): 923
1999, 44(14): 1537
C A. J Geodyn, 1986, 6:33
[8] Augus D F, Heflin M B. Geophys Res Let, 1995, 22(15): 1973 [9] Larson K M, Freymueller
J T, Philipsen
1540
926
[6] DeMets C, Gordon R G, Argus D F et al.. Geophys Res Let, 1994, 21(20): 2191 [7] Cook D B, Fujita K, MeMullen
376
2194
51 1976
S. J Geophys Res, 1997, 102(B5): 9961
9981
[10] Kogan M G, Steblov G M, King R W, et al.. Geophys Res Let, 2000, 27(14): 2041
2044
[11] Li Jinling, Wang Guangli.
t
Chinese Science Bulletin,
2000, 45(21):
1945-1948, Plate
[12] Tang Z H, Wang S H, Jin W J. Astron J, 2001, 121(2), (In press) [13] Tang Z H, Wang S H, Jin W J. Mon Not R Astron Soc, 2000, 319:717--720
252
2000 IVS Annual Report
ZOOcoo':! U. S. Naval Observatory
USNO Analysis
USNO Alan
Analysis L. Fev;
Center
David
A.
for
Boboltz,
Source
Ralph
A.
Center
Structure
Gaume,
for Source Structure
Report
Kerry
A.
Kingham
Abstract This report summarizes the activities of the United States Naval Observatory Analysis Center for Source Structure from its inception in January 2000 to the end of the calendar year 2000. The report forecasts activities planned for the year 2001.
1.
Analysis Tile
Center
Analysis
Observatory The
Operation
Center
for Source
main
structure
mission
information
Source
structure
sources
Research
into
the
out
emphasis
with
web
of the
Analysis
for use
in maintaining
information
for evaluating
The
Structure
is supported
and
operated
by the
United
States
Naval
(USNO).
is provided
for astrometric
effects for the
is to analyze the
in the and/or
of source
the
Analysis
VLBI
International
form
use and
on astrometric
long
term
Center
data
to extract
intrinsic
Celestial
Reference
Frame
(ICRF).
models
suitable
of synthesis
geodetic
structure
on improving
server
Center
images for long
of the
is provided
by the
source
term
position
stability
and
monitoring
determination
source
of sources. is also
carried
ICRF. USNO.
The
temporary
address
is:
http ://www. usno. navy. mil/RRFID/ The
Radio
Reference
frequency Both
the
raw
from
this
site.
(2000, also
Frame
intrinsic data
and
Links
processed
images
site
(with
the
USNO
with
their
Series,
devoted
web
sources
of the Vol.
exclusively
site
holds
infornlation
declination
associated
suitability
Supplement
web
(RRFID)
ICRF
astrometric
Journal
A new
Database
of most
to the
Astrophysical provided.
Image
structure
source
sources,
128,
to the
greater
pp.
models)
17 83 and
by
radio
degrees.
be
Fey
references
Center
the
-30
can
as derived
Analysis
on
than
obtained & Charlot
therein),
for Source
are
Structure
is
planned.
2.
Initial
Activities
In December Center
for
Jammry
and
charter
of the
radio
Structure
of the
frequency The
both a joint
to become
accepted
the
has,
of ICRF
since
database
degrees. used
Images for
mid
by the
an IVS IVS
is to provide of the
sources,
Analysis
Center.
a_s a Special
are
The
Associate
VLBI
collaboration
Report
between
frequency
database USNO,
structure Radio
images
at both
astrometric the
the
and
from
Goddard
models sources
of most
USNO
Analysis
Analysis
derived
Center
Frame
Image
and
Space
sources X
band
in
Flight
The Center
determina-
the
t)rimarily,
radio
intrinsic
with
(RRFID),
declination
(3.6 cm), are
RDV and
images, structure.
Database
Observations
observations.
IVS
include.,
from
on their
observations. RDV
to the
These
based
ICRF
(13 cm)
related
frame."
Reference
S band
geodetic
and
directly
reference
of the ICRF
hosted
available
products
celestial
intrinsic
quality
1996,
of radio
geodetic/astrometric
2000 IVS Annual
Center
maintenance
of the astrometric
a web accessible frequencies
and
images
USNO
-30
Analysis
"definition
an assessment
than
proposed
was
2000.
The tion
1999,
Source
the
the
greater standard
taken
experiments National
from are Radio
253
USNO Analysis Center for Source Structure
Astronomy
Observatory
(NRAO).
During
observed at S/X band using the with up to 10 additional geodetic provides a valuable resource used to define the ICRF. The
Analysis
Center
3.
Current
session,
about
70 ICRF
sources
are
for evaluating
the astrometric
has a program
on astrometric literature.
suitability
of active
position
of the extragalactic
research
determination.
investigating Results
the
of this
sources effects
program
of are
Activities
Since the inception processed and imaged. RDV10 is under way. The resultant
each 24 hour RDV
NRAO Very Long Baseline Array (VLBA) antennas together antennas. The resulting intrinsic source structure information
currently
intrinsic source structure published in the scientific
U. S. Naval Observatory
of the USNO Analysis Center, three These include the RDV07, RDV08
VLBA RDV experiments have been and RDV09 sessions. Processing of
RRFID has contributed data to the structure analysis "Structure Index" is available from Patrick Charlot at
of Fey & Charlot
http ://www.observ, u-bordeaux, fr/public/radio/PCharlot/structure, The USNO
and the Australia
research program ill Southern and ATNF accessible facilities.
Telescope
National
Hemisphere source These observations
Facility
(ATNF)
(2000).
The
html
are collaborating
in a VLBI
imaging and astrometry using USNO, ATNF are aimed specifically toward improvement of
tile ICRF in the Southern Hemisphere. Plans include strengthening the ICRF in the Southern Hemisphere by a) increasing the reference source density with additional S/X band (2.3/8.4 GHz) bandwidth synthesis astrometric VLBI observations, and b) VLBI imaging at 8.4 GHz of ICRF sources south of 5 = -20 °. These observations will provide a strong tie between the Northern and Southern Hemisphere through the overlap with common sources measured from the north. One 48 hour imaging
session
has been
carried
out and
is awaiting
correlation.
Several summer students contributed to the Analysis Center. Sarah Zelechosky used geodetic VLBI observations to image 3C418, finding evidence of superluminal motion. Ginger Leonard used RRFID data to classify ICRF sources according to the variability of their intrinsic structure. 4.
Staff The staff
and
of the Analysis
their responsibilities
Center
is drawn
from individuals
who work at the USNO.
are:
Name
Responsibilities
Alan L. Fey
Primary content,
scientific contact, Web and data base Webmaster, Web server administration,
design and VLBA
A. Boboltz
data analysis (imaging), structure analysis VLBA data analysis (imaging), structure analysis
Ralph
A. Gaume
Liaison
Kerry
A. Kingham
Web and data
David
The staff
to the ICRF
Product
base design
Center and content,
of the IERS Webmaster,
Web
server administration, geodetic data analysis (imaging), Mark 4 interface to imaging software, structure analysis
254
2000 IVS Annual Report
U. S. Naval
o
Observatory
Future The
following
activities
imaging
of VLBA
RDV
• Continue mination
research
of intrinsic
• Continue software
development
• Establish
a new web site devoted
Relevant
Publications
Structure
Center
into the effects
of an interface
products
observations
source
between
exclusively
of relevance
which
in the Southern
structure
the Mark
are currently
on astrometrie
4 correlator
to the Analysis
Hemisphere
Center
available
in col-
position
output
deter-
and the imaging
for Source
can be found
Structure
in the scientific
e.g.:
• "VLBA
Observations
ment Series, • "VLBA
August
of Radio
Observations Structure,"
No. 1, Pages
95-142).
• "The Proper Pages
Motion
Reference
1996 issue (Vol.
on Observed
of Radio
Frame
105, No. 2, Pages
Reference
Astrophysical
of 4C 39.25,"
Sources.
Frame
Journal
Astronomical
I.," Astrophysical
,Journal
Supple-
299-330).
Sources. Supplement
Journal,
II. Astrometric
Suitability
Series, July 1997 issue
December
1997, (Vol.
Based
(Vol. 111,
114, No. 6,
2284-2291).
• "Geodetic
VLBI
Observations
(Vol. 507, No. 2, Pages • "VLBA Additional 1, Pages
IVS
for Source
experiments imaging
Analysis
2000
Center
are planned:
• Make additional astrometric and laboration with ATNF partners
literature,
Analysis
Activities
• Continue
6.
USNO
Annual
Observations
of EGRET
Blazars,"
Astrophysical
Journal
November
1998,
706-725). of Radio
225 Sources,"
Reference
Astrophysical
Frame Journal
Sources. Supplement
III. Astrometric
Suitability
Series, May 2000 (Vol.
of an 128, No
17-83).
Report
255
U
U
ml
f"
, j J/_Uw
York
University/Space
Geodynamics
Canadian
Laboratory/CRESTech
VLBI
Canadian
Technology
, ......
VLBI
Technology
Development
i'ISyne C_m_om
Calvin
.:_
Development
Center
Center
Klatt
Abstract The the
Canadian
22 month The
ing
$2
Geodetic
development
correlator
and
VLBI
been
Center
has been
active
in a number
of areas
during
frequency
of capabilities
conducted
using
to make
significant
data
acquisition
switched
VLBI
observations,
for scheduling, the
advances
$2 VLBI
Algonquin,
data
fronts,
includ-
enhancement
utilization
processing
_llowknife
on many
system,
and
and the
of the
$2
of a transportable
analysis. Canadian
A number
of
Transportable
(CTVA).
(depending
$3,
VLBI
system
It is capable on system
continues
of 1 Gbit/sec
configuration)
to be
under
recording
using
robotic
active
development
with
unattended
tape
changers.
at the
Space
record
times
as long
effort
of the Space
Introduction The Canadian
dynamics
VLBI
Laboratory
Technology
of the Center
the Geodetic Survey Division dio Astrophysical Observatory Research Council of Canada, 2.
continues
to process
Laboratory.
as 160 hours
program
switched
next-generation,
GeodynaJnics
Development
frequency
expansion
have
Antenna
The
VLBI
of the the
experiments
Technology period.
capabilities
antenna
1.
VLBI
reporting
$2
VLBI
Development for Research
Center in Earth
is a collaborative
and Space Technology,
Geo-
(SGL/CRESTech),
of Natural Resources Canada (GSD/NRCan) and the Dominion Ra(DRAO) of the Herzberg Institute for Astrophysics of the National (DRAO/HIA/NRC).
Geodesy
Introduction The Canadian $2 geodetic VLBI program is developing a complete "end-to-end" geodetic VLBI system and operational capability. This effort involves a wide range of activities including development of the frequency switched $2 VLBI data acquisition system, enhancement of the $2 corrclator capabilities to process frequency and the expansion of capabilities $2 VLBI
Data
Acquisition
switched VLBI observations, utilization of a transportable for scheduling, data processing and analysis.
System
antenna
(S2-DAS)
The $2 VLBI data acquisition system is being jointly developed by SGL and the GSD. The S2DAS is designed to accomodate up to four VLBA/MkIV-type single sideband baseband converters (BBCs), each with a local oscillator (LO) independently frequency switchable under computer control. The objective of the development of the S2-DAS is to enable high sensitivity group delay measurements without appealing to a more costly parallel IF/baseband sub-system. There are currently four $2 DASs in use. An additional and one for BKG. These should be available for operational
three are in production: two for GSD testing within the first half of 2001.
The DAS Operating System (DASOS) has seen extensive Much effort has gone into frequency switching with automatic self tests
2000
(2000).
IVS Annual
The official release
Report
of DASOS
is t)lanned
development in the past 22 months. gain control (1999) and automated
to occur
in April
2001.
259
Canadian
VLBI Technology
Development
Center
front
DAS-PCFS communication requirements clock model is also underway.
$2
VLBI The
Canadian
CTVA
fi'ame
Control system
The
design
taken
on
SKED
(CTVA) acquired
The
through
analysis.
scheduling
experiment
CGLBI
8.2
9.1
available.
Minor
of $2
amount
wave-
In the December Of these,
VLBI and
multi-beam
changes
experiments work
possible VLBI
have (using
joined
assisted
drudging)
of the
filture
directions
(several
small
place and
work
for
focusses
in the
($2
CORE?)
antemlas
operations,
GSD
VLBt
experiment
and
for
reporting
period
has
place
both
CGLBI
CALC data
(see
to
below).
to investigate
geodesy.
with
ones)
large
in
experiments
for S2-based
co-observing
He
full automation
frequency-switched
taken
group.
of $2 support
we have
necessary
from
operations.
is at)proaching
remain
SOLVE)
VLBI
introduction
to f-SOLVE
to SOLVE
taken
is responsible
Recent
the
with
process
updated
SKED
B.C.
of Geodetic
recently
has
as a result
was
GSD
refer-
Canadian
Extensive testing through CGLBI ($2) will be moved to a new site in 2001.
has
and
(and
software
terrestrial of the
A the
An investiis underway.
website which is regularly updated to reflect experiment web site was created as a contribution to the IVS. This is documented elsewhere.
Experiments reporting period 2000) have been
17 were
participated Fringes
Penticton,
is
focussed
monitoring.
elements The
and
has
Analysis
Searle tasks
scheduling software
near
terminals
activity
of the
GPS
positions.
all aspects
was improved
GSD has produced a CGLBI (www.vlt)i.ca). An analysis documents SOLVE: f-SOLVE
Interferometric
length
Anthony
analysis
of simulation
performance into
and
involves
playback Recent
densification
Software to create Mk3-type databases from ($2) was written and has been used on a regular basis.
A number
The activity website
of a station
performance
with
station
at DRAO
$2
data.
system
and reliability. that the antenna
analysis
scheduling
The
fiducial
program
and
using
be colocated
Operations
VLBI
The
gation
Laboratory/CRESTech
Development
synthesis
to facilitate
will
located
Scheduling,
of scripts.
significant
t)een
system stability We anticipate
use
l)e analyzed. (CGLBIDB)
antenna
to provide
has
correlator to enhance
Antenna
through and
software
telescope
Geodetic
software.
station
VLBI
antenna
many
CGLBI
system
established.
bandwidth
radio
regions.
Ezperiment
experiment
the
the
Canadian
The
processing
sensitivity and has occurred.
Geodetic
is a six switched
System (CACS) development.
1997
on antenna experiments
has
is a 3.61n
in remote
Since
$2
of post
Transportable
The
Active CTVA
Corrclator
$2 frequency
deveh)pment
Canadian ence
$2
to handle
the
are being
Geodynamics
Correlator
designed on
York University/Space
24-hour
in 10 of these have
between
bccn
23 developmental performed using geodetic
experiments
experiments,
obtained
ALGOPARK
in each aim
experiments the $2 VLBI and
6 being $2
PENTICTN
the
24-hour
interferometric using
the
(CG006/June 1999 system, ALGOPARK
remainder
were
system
through CG028/ and the CTVA. tests.
Yellowknife
geodetic. experiment. $2 system
The ha_s been
measured repeatable
baseline within
cnl.
260
2000
IVS
Annual
Report
1
"fork
University/Space
Geod)'namics
Laboratory/CRESTech
Canadian
ALGOPARK-CTVADRAO 65O
Basehne
Length
$2
VLgl
VLBI
Technology
Development
Center
Results
i
i CGLBI
Da_a
64.0
E
630
oo
i
,
o
r !
04 620
o
!
+ii'
'
610
600
590
I
h
I
L
L
200
300
400
500
600
Days
Figure
3.
$3
Wide
VLBI
1. Penticton
Bandwidth
applications
- Algonquin
VLBI
to geodesy
Data and
since
Jan
$2
1
lgg9
Baseline
Length
Measurements
Record/Playback
astrophysics
i 700
System
can benefit
fronl
Development
higher
signal
to noise
ratio
observations. The most attractive means of achieving large factor improvements in SNR in geodetic VLBI observations is by developing wide bandwidth VLBI data record/playback/correlation systems. Tim
Space
Geodynamics
Toronto, Canada designated "$3",
Laboratory
(SGL)
located
on the
is developing a family of wide bandwidth VLBI as a next generation follow-on to the "$2".
campus
of York
University
data
record/playback
in
systems
The $2 VLBI data record/playback system is a 128 Mbit/sec, Mostly-Off-The-Shelf (MOTS) VLBI data record/playback system t)a_sed on an array of eight video tape transports together with custom designed signal channel cards and a single board control computer housed in a standard VME enclosure. The $2 is specified to operate without error correction coding at a Bit Error Rate (BER) of the order of 10-4; however typical BER performance in the $2 is of the order of 10 -5. The extensive use of MOTS VLBI data record/playback now in use in a variety around the world.
hardware in the $2 design resulted in a tow cost, high performance, system of which more than 50 have been fabricated at SGL and are
of radio
astronomy
and VLBI
applications
in more than
a dozen countries
The $3 VLBI data record/t)layback system is the next generation MOTS VLBI system. It has inherited a significant amount of its architecture fl'om the $2 although the VME backplane has been replaced with a wide bandwidth Compact PCI backplane. In addition the interface for the $3 will be compatible with the VLBI Standard Interface (VSI) specification. The $3 is constructed as an array
of eight JVC "Digital-S"
(now designated
"D9")
digital
video
which is able to record/playback VLBI data at a rate of 150 Mbit/sec, "user data", for an overall user data rate of 1024 Mbit/sec (1 Gbit/sec).
2000
IVS
Annual
Report
tape
transports,
of which Recent
each of
128 Mbit/sec is $3 system tests
261
Canadian VLBITechnology Develol)ment Center
YorkUniversity/Space Geodynamics Laboratory/CRESTech
at SGL in which pseudorandom digital data was written to and read from the $3 tape transport indicate that ttle signal to noise ratio on the $3 eye pattern is comparable to that of the $2. The $3 is expected to provide a BER performance that is comparable to the $2. The tape change interval for the $3 tape array is 2.5 hours at a data rate of 1024 Mbit/sec
(1
Gbit/sec) with longer tape change intervals being possible when operating the $3 at reduced data rates. Tile cost of recording media for the $3 is expected to be $150 (US) per hour at a data rate of 1024 Mbit/sec (1 Gbit/sec). Tile $3 VLBI data record/playback recently introduced will record/playback
system
is designed
for systein
JVC High Definition TV "D9-HD" tape transport, VLBI data at a rate of 300 Mbit/sec. The D9-HD
upgrades
based
on
the
which in the $3 context will enable the fabrication
of the "Compact" version of the $3 system, the "$3-C", which will record/playback VLBI data a rate of 1024 Mbit/see (1 Gbit/sec) on a compact array of only four tape transports. The D9-HD will also enable the fabrication "S3-E", which will record/playback VLBI data of eight tape at data rates SGL has record/playback
of the "Extended" version of the $3 system, the at a rate of 2048 Mbit/see (2 Gbit/sec) on an array
transports. Dual operation of the S3-E will provide as high as 4096 Mbit/sec (4 Gbit/sec). implemented systems.
at
a TiltRac robotic The tape changer
for VLBI
data
tape changer for the $3 family is u true Commercial-Off-The-Shelf
record/playback of VLBI (COTS)
data sys-
tem developed especially for use with the JVC D9 and D9-HD tape transports. The robotic tape changer is available in single-bay, dual-bay, and triple-bay configurations. SGL ha_ implemented a dual-bay configuration in its development system. The robotic tape changer provides the option of long unattended
operation
intervals
with the $3 family
of VLBI
Unattended System Config
Data Rate (Mbps)
$3
$3-C
S3-E
Table
262
Tape Duration (Hrs)
Single Bay Robot
data
Operation
record/playback
(Hrs)
Double Bay Robot
_iple Bay Robot
1024 512
2.5 5
65 130
130 260
256 128
10 20
260 520
520 1040
1024
1.25
32.5
97.5
162.5
512 256
2.5 5
65 130
195 390
325 650
2048 1024
1.25 2.5
32.5 65
65 130
512 256
5 10
130 260
260 520
Dual
4096
1.25
32.5
65
S3-E
2048 1024 512
2.5 5 10
65 130 260
130 260 520
1. $3 Tape
Durations
and
Unattended
Operating
Times
with
systems.
Robotic
Tape
2000
Changer
IVS Annual
Report
Kashima
Space
Research
Center,
Communications
Technology
Research
Laboratory
Development Tetsuro
Technology
Center
Development
at
Center
at CRL
CRL
Kondo
Abstract Communications Japan
and
has
report gives activities.
1.
Research been
keeping
a review
of the
Laboratory high
(CRL)
activities
Technology
has led
in both
the
development
observations
Development
Center
and (TDC)
of the
VLBI
technical at CRL
technique
in
developments.
This
summarizes
recent
and
Introduction Communications
Research
Laboratory
(CRL)
has been
leading
the development
of the VLBI
system in Japan since the development of the K3 VLBI system in 1979 which is compatible with the Mark III VLBI system developed by the US group. CRL then developed the K4 VLBI system, which facilitated ease in both operation and transportation. In October 1990, the International Earth
Rotation
Service
(IERS)
designated
the Communications
Research
Laboratory
(CRL)
and
Haystack Observatory (in the United States) as Technical Development Centers (TDC). In September 1996, the IERS directing board designated CRL as TDC again. The function of the IERS VLBI Technical Development Center was taken over by the IVS Technology Development Center after its establishment on March 1, 1999. Since then CRL has participated in IVS as one of its Technology Development Centers. community of its current following 2. 2.1.
The CRL-TDC newsletter activities. The newsletter
is published biannually is also available through
to inform the VLBI the Internet at the
URL http://www.crl.go.jp/ka/radioastro/tdc/index.html.
Recent
Activities
Real-Time
VLBI
The Keystone over 2 cm/month
(KSP) real-time VLBI on the Kashima-Tateyama
[1] system observed extraordinary crustal deformation of baseline during July-August 2000 (Fig.l). It occurred
just after the volcanic eruption event at Miyake Island about 150 km south of Tokyo at the end of June. To provide data to the Headquarters for Earthquake Research Promotion more frequently, we changed a 24-hour session frequency from every two days to every day. Every-day continued till November when the crustal deformation seemed to be well settled.
observation During this
period we had no technical problems in real-time VLBI operation. Although it was planned to terminate the Keystone project at the end of March, 2001, it was decided from the importance of KSP observation to extend the term of the project for one more year with three stations, Kashima, Koganei, and Tateyama. This real-time VLBI technique is also 34-m antenna at Kashima so as to realize
used to connect a large virtual
a 64-m antenna radio telescope.
at USUDA and a A test observation
was successfully carried out in December 1998, then this project was named GALAXY carried out radio astronomical observations once every several months. The GALAXY carried out in collaboration with the Institute of Space and Astronautical Science (ISAS), Astronomical
2000
IVS
Annual
Observatory
Report
(NAO),
and Nippon
Telegraph
and Telephone
Corporation
and has has been National (NTT)[2].
263
Technology
Development
Center
at
CRL
Kashima
Space
Research
Center,
Communications
Research
Laboratory
#%
Figure
1.
Kashima-Tateyama
baseline
length
Figure 2. PCI sampler VLBI system.
change. Extraordinary crustal deformation over 2 cm/month was observed during July-August 2000.
board
for tile IP-
In the KSP real-time VLBI system, data axe transmitted through the high-speed ATM network. However, network cost is still expensive and connection sites are still limited, so that ATM-VLBI is not yet well generalized. We therefore aimed to develop a new real-time IP (Internet protocol) technology that has already spread widely, to reduce expand
the connection
sites of network.
We call this system
"IP-VLBI"
VLBI system using network cost and to
or "VLBI
over IP",
and
started the development in late 1999. We have been developing the PC-based IP-VLBI system consisting of a PCI-bus sampler board (Fig.2) and PC software to make real-time data transmission and reception. We also intend to carry out real-time correlation by PC software. One sampler board has 4 video signal inputs and is designed to be able to sample each signal with a frequency of up to 16 MHz for 1 bit A/D. sources. Research
The sampler
board
has been tested
Real-time characteristics have been evaluated Center. So far we can confirm the sufficient
by using actual
signals
from radio
by using the LAN at the Kashima performance of "coherent sampling"
Space up to
8 MHz sampling. Although the performance of 16 MHz sampling has not yet been confirmed, will be checked soon. Regarding the "real-time correlation processing" by using PC software, can process 2 MHz sampling data in real-time at present to make correlation processing faster is in progress[3]. 2.2.
Giga-bit The
VLBI
developments
time.
An improvement
it we
in the algorithm
System of the
giga-bit
VLBI
system
at the
Communications
Research
Labora-
tory started in 1996. The system consists of the A/D sampler unit (TDS580D/TDS784A), recorder system (GBR1000), the correlator (GICO), sampler interface unit, the timing control (DRA1000), and the data buffer unit (DRA2000). In 1998, first fringes on the Kashima-Koganei baseline using this system.
were successfully
the unit
detected
During 1999 - 2000, four geodetic VLBI experiments were performed using the giga-bit VLBI system. Two of them are on the Kashima-Koganei baseline and others axe on the Kashima-Gifu baseline
(about
360 km).
In each experiment,
observations
were performed
with K4 VLBI
system
in parallel to compare the results. As the sampling frequency of giga-bit system (1024MHz) is much higher than that of K4 system (16 MHz), performance of the giga-bit system is influenced by the stability of the sampling frequency. By developing a inethod to compensate for the sampling
264
2000
IVS
Annual
Report
Kashima Space Research Center, Communications Research Laboratory
jitter
using
a superimposed
tone signal,
data
quality
and estimation
a level comparable to the K4 VLBI system [4]. A new compact VSI Gbps sampler, ADS-1000, started
to provide
a simple
portable
Gbps sampler.
will eliminate long analog transmission 50 kg and occupy 6U in the system,
has been Antenna
in near future. the ADS-1000
(Fig.3). Sampling jitter is expected to be reduced is directly supplied from a PLO. As a remarkable Standard Hardware Interface) compatible. LVDS devices have been examined and
Technology Development Center at CRL
errors
have been
developed. front-end
A design
mounted
According to the endorsed document this is CRL's first VSI-H instrument.
Oversea
corporation. [5]. h
I
They
pact
2.3.
VSI Gbps
VLBI
sampler
Standard
under
test.
Figure
weigh 1/2U
VSI-H proposal, The ADS-1000
are venture
companies
Kashima
DRAZ_
_ Domestc.
C
ReaJtlme
the new com-
of ADS-1000
by using a high purity-sampling signal which feature, the sampler output is VSI-H (VLBI
Derr_st_c
3. ADS-1000,
to
with AD samplers
Although, the current AD packages weigh less than 10 kg and occupies
is manufactured by DigitalLink Co.Ltd. and Venetex which are distinguished by advanced digital technology
Figure
improved
4. Proposed
for the global
Gbit
VLBI
Station
system
enhaJlcement
baseline.
Interface
CRL TDC has been contributing to the establishment of the VLBI standard interface (VSI) with Dr. Alan R. Whitney, Technology Coordinator of IVS. We had international telephone conferences several times to discuss VSI and reached the agreed specification VSI-H Vet1.0 was opened to public in August, 2000. It can be accessed (http://dopey.haystack.edu/vsi/)
or Japanese
VSI homepage
of VSI hardware (VSI-H). through the VSI homepage
(http://www2.crl.go.jp/
ka/radioastro/tdc/ivs/vsi/). We are adapting VSI-H to $2-K4 copying system and VSI-based K4 data acquisition system. One of the motivations was the request for a $2-K4 data copying system. Antarctica VLBI data observed in 1997-1999 and Pulsar VLBI observation data are recorded on an $2 system. These data axe desired to be correlated with K4-type (K4, KSP) correlators because of easiness to handle it in Japan. Also $2-K4 copier will expand the ability of organizing VLBI network observation [6]. Late 2000 supplementary budget to make upgrade of the giga-bit VLBI system was approved. The importance of the parallel data transmission is recognized again in the VSI-H, while IT technology
promoted
high-speed
serial transmission
by IP. All the VLBI
instruments
in the Gbps
system developed by CRL will adopt VSI-H. We also intend to encourage the application of the VSI interface to a wide scientific use through the demonstration that will be made using the
2000 IVS Annual Report
265
Technology
Development
upgraded
giga-bit
in Fig.4.
Upgraded
disposed Gbps
to
each
The
countries.
and as the
TDC
them
Gbit
as
K4
and/or
While
VSI
the
Gbit
a robot
correlator
equipped
with
to open are
VLBI
system
and tape
this
will
planned
is being
will continue
will start
VLBI
are
increase
exchanger
ports
other
is shown
ADS-1000
UWBC-GICO
VSI-H
in the
also
Research Laboratory
samplers,
is doubled
system,
supplies
Gbit
new
recorders
experimental
is promised related
enhanced and
KSP
correlator
CRL-TDC
cost)
to make
to actual
of the
running
Internet
of the
and
will continue
as possible.
succession
(lower
number
Gbit
supports
of the
introduced
well
Center, Communications
operation.
groups
and
new
[7].
Perspectives
to apply soon
of the
plan are
observation.
Technical
CRL
As
Space Research
recorders
multi-baseline
system
Future
The
sites.
Kashima
Preliminary
data
station.
a new
correlator
system.
Gbit
for automatic
its operation,
3.
VLBI
observation
designed
Center at CRL
observations.
We also
continue
current and
efforts
new
In particular, the
real-time
flexible
to develop
connections
we will
development
VLBI
of the
technique between
technologies
but
VLBI
introduced
demonstrate "Internet
aims
stations
at
in this
VSI-H VLBI"
realizing
by using
the
report
instruments
system
which
more
economical
Next
Generation
is
(NGI).
References [1] Kiuchi, H., M. Imae, T. Kondo, M. Sekido, S. Hama, T. Hoshino, H. Uose, and T. Yamamoto, Time VLBI System Using ATM Network, IEEE Trans. Geosci. Remote Sensing, Vol.38, No.3, 1297,2000.
Real1290-
[2] Takahashi, Y., H. Kiuchi, A. Kaneko, S. Hama, J. Nakajima, N. Kurihara, T. Yoshino, T. Kondo, Y. Koyama, M. Sekido, J. Amagai, K. Sebata, N. Kawaguchi, H. Kobayashi, M. Iguchi, T. Miyaji, H. Uose, and T. Hoshino, The plan of the big virtual telescope using the high speed communications network, Technical Development Center News CRL, No.13, 17-19, 1998. [3] Kondo, T, Y. Koyama, M. Sekido, J. Nakajima, H. Okubo, H. Osaki, S. Nakagawa, and Y. Ichikawa, Development of the new real-time VLBI technique using the Internet Protocol, Technical Development Center News CRL, No.17, 22-24, 2000. [4] Koyama, system, [5] Nakajima, ADS-1000 [6] Sekido, copying
Y., J. Nakajima, M. Sekido, and T. Kondo, Geodetic VLBI experiments Technical Development Center News CRL, No.17, 15-17, 2000. J., M. Sekido, and development status, M., J. Nakajima, system and data
T. Suzuyama, Another Technical Development
sampler prototype, News CRL, No.17,
VLBI
nearly completion; 18, 2000.
Y. Koyama, T. Suzuyama, and T. Kondo, Development of VSI-based $2-K4 sampler, Technical Development Center News CRL, No.17, 19-21, 2000.
[7] Nakajima, J., Y. Koyama, M. Sekido, R. Ichikawa, system expansion, Technical Development Center
266
giga-bit Center
using giga-bit
and T. Kondo, Approved upgrade News CRL, No.17, 25, 2000.
of the Gbit
2000 IVS Annual
VLBI
Report
' "
"
55577 5d-
Forsvarets forskningsinstitutt
Combination
(FFI) (Norwegian Defence Research Establishment)
of VLBI,
GPS
Per
and SLR FFI Helge
FFI Tech. Development Center
Software
Development
at
Andersen
Abstract FFI's contribution to the IVS as a Technology Development Center will focus primarily on the development and validation of the GEOSAT software for a combined analysis at the observation level of data from VLBI, GPS and SLR. This report briefly summarises the latest improvements of the GEOSAT software. FFI is currently Analysis Center for IVS and ILRS, Technology Development Center for IVS, and Combination Research Center for IERS. 1.
The
GEOSAT
software
The advantages of the combination of independent and complementary the observation level is discussed in Andersen ([1]). The models of GEOSAT ([2]). Recent changes are described in the following. The GEOSAT software has recently extended the analysis
capability
space geodetic data at are listed in Andersen
from 30 to 60 GPS stations
per day. In addition, a new procedure for the generation of a priori GPS orbits for the filter been implemented. A three day IGS precise orbit for each GPS satellite is used as observations the determination
of a GEOSAT-generated
nine solar radiation day orbital dataset
GPS orbit.
In this fit six orbital
elements
in addition
has for to
pressure (SRP) parameters are solved for. The rms of residual fit for the threeis typically between 2 and 4 cm for all satellites except for 2-4 satellites where
the rms is significantly larger. The estimated orbit is used to generate a priori observation residuals and observation partial derivatives to be used in the filter where all data types are combined. In the 24 hour filter solution the nine-parameter SRP model are kept fixed and only the six orbital elements
and one SRP-scaling
one-day orbits will be based of orbital fit two additional
parameter
and a Y-bias
parameter
are solved
for.
In this way the
on a very realistic SRP model. However, for satellites with large rms stochastic velocity change parameters are solved for. Experiments
with the IGS precise orbits show that this parameterization is sufficient in order to fit a 24 hour GEOSAT-generated GPS orbit for all satellites including the outlier satellites with an rms of 2-3 cm in each coordinate. A significant part of the 2-3 cm difference is due to the use of inconsistent values for the EOPs. EOP values are taken from IERS and not the IGS EOP estimates to be used with the precise IGS orbits. In conclusion, a highly sophisticated GPS orbit strategy has been established. The use of a large number of GPS stations in combination with a moderate number of dynamical
solve-for
parameters
and
a realistic
dynamical
orbits with a precision level of a few cm in each coordinate. It is a fact that the position of the effective phase center GPS
satellites
is not very well known.
model
is expected
of the
This leads to a scale inconsistency
approximately 2 ppb. It is therefore a standard procedure in analysis the z-coordinate of the mean position of the transmitter phase center. only possible of a reference absolute
to determine the phase center satellite. Since the GPS data
positions
of the phase
2000 IVS Annual Report
center
transmitter
to result antenna
in GPS of the
with VLBI
and SLR of
with GEOSAT With GPS-data
to estimate alone it is
position relative to the position of the phase center in our case are combined with VLBI and SLR data
of all satellites
can be determined.
267
FFI
Tech.
Development
Center
Forsvarets
Another possible candidate pospheric mapping function. analyzed
forskningsinstitutt
(Norwegian
Defence
Research
Establishment)
for scale inconsistency between the different techniques is the troIn order to be consistent with VLBI and GPS the SLR data are
with the use of the dry NMF
signal delay in the zenith procedure is in accordance
(FFI)
function
which
is used for VLBI
direction is however calculated with recent recommendations
mapping
using given
the Marini-Murray by Richard Eanes.
tidal geocenter motion is implemented (Watkins and Eanes, [3]). In GEOSAT data from the different techniques are combined called an arc. The state vectors and complete number of independent arcs of space geodetic
in batches
and
GPS.
The
model. This A model for
of one day which
is
variance-covariance matrices from the analyses of a data can be combined using the CSRIFS (Combined
Square Root Information Filter and Smoother) program. any parameter can, at each level, either be represented
Four parameter levels are available and as a constant or a stochastic parameter
(white noise, colored noise, or random walk). The batch length (i.e. the time interval between the addition of noise to the SRIF array) can be made time- and parameter dependent. More details can be found 2.
in Andersen
([1]).
Prospects
Two new programs in the GEOSAT system are under development. The IERS program will transform the output from internal reference frames in GEOSAT to the external reference frames of the IERS. Also the final combined covariance matrix of CSRIFS will be rotated. The SINEX program
will write
the global
solution
in the SINEX
format.
Statens kartverk has recently received a copy of the GEOSAT software. The GEOSAT software will be converted to PC/LINUX in the near future. 3.
Technical Table
Staff
1 lists the FFI staff involved
in IVS activities.
Table 1. Staff working at the FFI AC and TDC I Name
t Background
] Dedication
I Agency
]
I Per Helge Andersen
I
l
I
]
geodesy
40%
FFI
References [1] Andersen, 531-551.
P. H. Multi-level arc combination
[2] Andersen, P. H. High-precision NDRE/Publication 95/01094.
station
with stochastic
positioning
parameters.
and satellite
Journal
orbit determination.
[3] Watkins M., Eanes R. Observations of tidally coherent diurnal and semidiurnal center. Geophysical Research Letters, Vol. 24, No. 17, 2231-2234, Sep 1, 1997.
268
of Geodesy (2000) 74: PhD Thesis,
variations
2000
IVS
in the geo-
Annual
Report
/
l
NASAGoddard Space FlightCenter
GSFC
IVS
GSFC
Technology
Ed Himwich,
Development Nancy
Technology
Center
Vandenberg,
Tom
Development
Center
Report
Clark
Abstract This report establishment The
GSFC
System
IVS Technology
(FS),
scheduling
summarizes the activities of the of IVS to the end of 2000. The scheduling
algorithms,
implementation,
1.
The
GSFC
rithms,
and
and provides
station
tools a pool
software
for station
including
timing
of individuals
the
Field
and meteorology,
to assist
with
station
Operation
Development
procedures.
develops
including
Center from the for the year 2001.
and training.
Center
IVS Technology
IVS Technology Development forecasts activities planned
(TDC)
hardware
procedures,
upgrades,
Development
operational
Center
(SKED),
operational
check-out,
Technology
Development
software
GSFC report
Center
It provides
(TDC)
manpower
develops for station
hardware,
software,
visits for training
algoand up-
grades. There are other techology development areas at GSFC covered by other IVS components such as the GSFC Analysis Center. The current staff of the GSFC TDC consists of Tom Clark, Nancy Vandenberg, Ed Himwich, Chuck Kodak, Raymond Gonzalez, and William Wildes. The remainder of this report covers the status of the currently 2.
being
main
areas
of development
that
are
pursued.
Field
System
During
this period
two major
new features
were released:
Y2K support
and mode
independent
parity checks. Y2K support was of course necessary for continued operation of the FS in the year 2000 and beyond. Mode independent parity checks removed the need for stations to change parity check procedures for every experiment that used a different mode than the previous experiment. In addition several new features under development during this period will be released in the next major release, 9.5. Some of the features included are: (1) Support for K4 systems, (2) support for sequential use of two longitudinal tape recorders, (3) better handling of default values for Mark III/IV IF attenuators, (4) a utility "msg" for sending Ready, Start, and End messages for geodetic sessions, (5) support for report logging maser offset data from a TAC, (6) support for NTP, (7) a command, "ifadjust" to automate determining the IF attenuator settings for a given mode, (8) an experimental tool for monitoring FS operation remotely, ARTS, (9) a command, "tnx" to disable reporting of an error message that can't be fixed, and (10) an experimental display only error messages to make it easier for the operator to keep track is expected in the first quarter of 2001. In the following FS release, 9.6, several (1) dual
head
recording
for Mark
IV and
other
improvements
VLBA4,
(2) support
program, "erchk" to of them. This release
are expected; for the
among
new Mark
these
axe:
IV firmware,
(3) onsource flagging formatted in AIPS flagging file format, (4) improved Tsys measurements with automatically generated procedure files, frequency dependent noise diode temperatures, and ANTTAB scans.
2000
IVS
file format
The release
Annual
output,
is expected
Report
(5) faster the third
set-up quarter
when
the formatter
set-up
doesn't
change
between
of 2001.
269
:!
GSFC Technology Development Center
3.
SKED
and
The GSFC
NASA Goddard Space Flight Center
DRUDG Technology
Development
Center
is responsible
for development,
maintenance,
and
documentation of the SKED and DRUDG programs. These two programs operate as a pair for preparation of the detailed observing schedule for a VLBI session and its proper execution in the field. VEX release
During 2000 SKED was enhanced to add new user interface features, the ability to write files, and K4 and $2 scheduling support. Some bugs remain to be worked out before official of the new SKED
• A Java-based
version.
Meanwhile
user interface
engineering
student
was added
on a trainee
users are testing to SKED
program
and using the available
by Kristian
sponsored
Refinetti,
by NVI/GSFC.
version.
a Chalmers
University
The SKED
can now be accessed with a set of screens that make selection of sources, modes, and scheduling parameters more powerful and flexible.
catalog
stations,
observing
• New SKED commands to generate a VEX file from the schedule file were added. file is required as input to the Mark IV correlators. The native SKED format standard
schedule
• Scheduling
file format
support
for K4 and
could be easily generated arc handled in the native 4.
VLBI
day)
At Goddard, GPS-based
and the VEX file is only an output $2 systems
was added
for these recording systems. units for each system.
The VEX is still the
format.
to SKED Displays
files
so that
of tape
geodetic
schedules
usage and tape
speed
Timing we have continued to stress the development of high accuracy (,_20 nsec for each timing measurements at VLBI stations; this data is needed for several reasons:
• Correlator efficiency is improved significantly if the relative station --,50 nsec level and clock drift rates are known at levels _1:1013. • To produce accurate a few hundred nsec. • Discontinuities seen hydrogen masers. After
much
discussion
• Run continuously, • Be easily • Produce
UT1 measurements,
in timing
we decided
logging
reproducible daily timing
data
data
clocks
are an excellent that
need
are known
at the
to be tied to UTC(USNO)
diagnostic
the ideal timing
between
at all stations accuracy
station
clocks
system
of performance for VLBI
problems
stations
to
in
would
experiments,
and be low cost,
of 20-30 nsec anywhere
in the world.
Our R&D testing beginning in 1993 showed that we could meet the accuracy goal with a particular low-cost GPS receiver (the Motorola PVT-6) and by 1995, we distributed ,,_50 timing clocks for the community - for humorous reasons, these receivers were named the TAC Totally
Accurate
Clock.
The
historical
archives
at ftp://aleph.gsfc.nasa.gov/GPS/totally.accurate.clock. TAC32Plus is a VLBI "plug in". Some of the of this report ("Recommended Clock and Timing
270
of the VLBI Setup
early
TAC
development
are
available
The current software package, called features are depicted in the final figure for a Mark4 VLBI Station") and include:
2000 IVS Annual Report
NASA Goddard Space Flight Center
• Full-time
logging
• Automatic to-peak
of Time
application
Interval
smoothed
• Providing
station-wide
to timing
• Full support
Counter
of corrections
with the ONCORE)
• Providing
• Access
GSFC Technology Development Center
data
data
to disk in a "friendly"
for quantization
inherent
TIC data
(TIC)
dither
(amounting
format,
to 104 nsec peak-
in the GPS receivers,
to the VLBI
system
via a TELNET
network
computer
synchronization
via FTP
for remote
maintenance
for TIC+TAC+TAC32Plus
system
socket,
using NTP, and
is included
diagnostics. in the LINUX
PC Field
System.
Before May 2000, timing performance was limited by the U.S. Dept. of Defense through a process called Selective Availability (SA). With SA, the atomic clock onboard each GPS satellite was "diddled" with a pseudo-random code that spoiled the spectral purity of GPS timing signal in the range
from a few seconds
to ,-,1/2
hour.
With
the TAC, we provided
some mitigation
against
SA by averaging the timing over all satellites in view, and by averaging timing over many minutes in the time domain. With this process, the ONCORE-based TACs routinely yield timing smooth at the 15-20 nsec level at all times from minutes to a day. After May 2nd when SA was turned off, the short-term improved signature data
stability,
as judged
by taking
from -_15 nsec to _5 nsec. of the ionosphere, amounting
the RMS noise of all samples
The dominant error source to ,,_15 nsec peak-to-peak.
suddenly
in a 5 minute
window,
became
diurnal
the
Data was logged during a 9 week period at the end of 2000 with an ONCORE receiver and the system described above logging the H-Maser at GGAO in Greenbelt. The Maser had a rate
offset of ,-_20 nsec/day (a frequency to increase, which was subsequently
error of ,_2.4 x 10-13). traced to a temperature
ure demonstrating
at ftp://aleph.gsfc.nasa.gov/ivscc/annual_report/2OOO/oncore-
ggao.ps. In late ceiver that
this is available
1999, Motorola had been used
announced that they were discontinuing the ONCORE VP rein the TAC-2 and CNS GPS clocks. We began to work with a
software developer who had made an excellent Where the ONCORE VP shows --_4 nsec noise shows
,_650
psec
of noise,
On Nov.22, the drift rate was observed change at the H-Maser chamber. A fig-
a factor
timing in the
,,,5 better.
receiver 5 minute
A figure
based on the samples, the
demonstrating
this
SiRF-1 chipset. SiRF prototype is available
at
ftp :/ / aleph.gsfc.nasa.gov / ivscc / annual_report / 2OOO/ sirf*ggao.ps. A paper on these receiver developments was presented at the Sept.2000 ION meeting (T.Clark, R.Hambly and R.Abtahi "Low Cost, High Accuracy GPS Timing", Proceedings of Institute of Navigation GPS www.gpstime.com. 5.
New
2000,
Meteorological
Salt Lake
City,
pp.905-913
Meteorological
Sensor
425A/AH) both available from install these at NASA supported
2000 IVS Annual Report
and
copies
are available
on http://
Sensors
GSFC has investigated new meteorological sensors in use at many sites. We are planning MET-3A
(2000))
Part
#1539-001
Paroscientific sites within
sensors to replace the aging standard CDP-era to provide FS support for the following devices: and
Handar
425 Ultrasonic
at http://www.paroscientific.com. the next year.
Wind
Sensor
(Model
We expect
to
271
GSFC
Technology
Development
Center
NASA
dlldOJ-
Goddard
Space
Flight
Center
IVS
Annual
Report
S,NOIJ.V.LS
E 0
zoo
272
L
2000
z/
MIT
Z
/
Haystack
Observatory
...S 2, S 7!,2
Haystack
Haystack
Observatory
Observatory
Technology Alan
Technology
Development
Development
Center
Center
Whitney
Abstract Current Mark
work
in VLBI
IV correlator
system,
record/playback likely
1.
system,
incorporate
Mark
IV
technology
at Haystack
plus
initiative
that
magnetic
a new
will utilize discs
as the
Observatory
to develop
mostly storage
includes
a low-cost
further
development
of the
Mark
V VLBI
high-performance
commercial-off-the-shelf
(COTS)
technology
and
most
media.
Correlator
Mark IV correlators have been operational at USNO, MPI, JIVE and Haystack for about a year and have now completely replaced the Mark IIIA correlators. Haystack Observatory maintains the software
for the USNO,
MPI and Haystack
installations.
Before the changeover from the Mark IIIA correlators cross comparison tests were done to ensure that the Mark In fact, the first published
results
from the Mark
to the Mark IV correlators, IV results were of the highest
IV correlators
the changeover from the Mark IIIA correlator. The Mark IV correlator software has been continuously new operational capabilities and efficiency improvements,
of Mark
• GUI control
auto
extraction
• Bar-code-driven
tape
• Transparent
• Full configuration
post-correlation
• Multiple-stream
formats
by a set of VEX-format
files
package will be:
processing
(multiple
simultaneous
independent
scans)
synchronization
• 'Double-speed'
IVS Annual
to be
control
specified
Soon to be implemented
2000
more improvements
library
file-version
tape
tape
with still
2-bit samples
• Full phase-cal
• Faster
IV and VLBA
after
and cross-correlation
for 1 and
• HOPS
Mark
2 months
interface
• Simultaneous • Support
IIIA,
less than
improved over the past year to include and all Mark IV correlators are now
operating at an efficiency exceeding that of the Mark IIIA, made. Some of the features that are now supported are: • Processing
occurred
extensive integrity.
Report
tape
playback,
followed
by 'qudruple-speed'
tape
playback
273
Haystack
2.
Observatory
Mark
Technology
V VLBI
With
support
Mark V VLBI
Data
Development
System
from NASA,
record/playback
Center
MIT
Haystack
Observatory
Development
JIVE system
and
NRAO,
based
Haystack
Observatory
on the requirements
is now developing
for the next generation
the
of VLBI
systems: • Minimum
of 1 Gb/sec
data
rate
• Economically
upgradeable/expandable
to ,-_ 8 Gb/sec
• Design
primarily
off-the-shelf
based
• Modular, • Robust • Easy
easily
on unmodified
upgradeable
operation,
as better/cheaper
low maintenance
over the coming
subsystems
technology
and
becomes
decade
components available
cost
transportability
• Conformance
to VLBI
• Flexibility data
to support
• Minimum
of 24-hour
Standard
Interface
electronic
transfer
unattended
(VSI) specification ('e-VLBI')
operation
and
computer
processing
of recorded
at 1 Gb/sec
Though this list of goals may appear idealistic, we believe they can be achieved in a system which can be designed today, and which will evolve in the following years to even higher data rates and additional 2.1.
storage
capacity
Magnetic Though
discs
both
with minimal on
magnetic
the
way
additional
engineering
to surpassing
disc technology
effort.
tape
and magnetic
tape
technology
have made great
strides
over the past few years, the pace of magnetic disc development has been so great that it is very likely that disc storage will become cheaper than magnetic tape storage by ,-_ 2004. This trend can be clearly seen in Figure 1, where the $/GB for both disc drives and magnetic tape media (including projections
for LTO tape
media,
which we focused
on in the original
COTS
concept
proposal)
are
plotted as a function of time. In addition are shown two 1998 projections for disc- storage costs_ one from IBM and the other from the National Storage Industry Consortium (NSIC); the latter suggests a tape-to-disc crossover in the latter part of this decade. However, it is clear that the cost decreases of magnetic disc storage have dramatically accelerated over the past two years, far exceeding industry projections of only 3 years ago, and show no signs of ceasing. Current disc industry
predictions
suggest
that
in 2004 the cost per GB will be ,-, $.30 for low-cost
'dimestore'
IDE (aka ATA) drives, but even these predictions may well prove conservative. As you can see from Figure 1, by _ 2004-5 the cost of disc drive storage is expected to fall below that of magnetic tape. Magnetic tape industry predictions have historically been pretty much on target and are expected to continue to be so, provided magnetic tape can even survive in the face of magnetic disc progress! Furthermore, note that the costs shown in Figure 1 are for complete disc drive units, while the tape The reason is perhaps apparent Magnetic 274
costs are for the magnetic for this happening is quite
two orders
of magnitude
tape media, ignoring the substantial cost of tape drives. clear - the flow of money into magnetic disc development
greater
obstacles to the current breakneck disc area-bit-densities on modern
than
that
for magnetic
tape!
The disc industry
sees no
pace of development for at least several more years. discs now (in early 2001) are ,,_ 15 Gb/in 2, and are 2000
IVS
Annual
Report
MIT Haystack Observatory
expected
Haystack Observatory Technology Development Center
to rise to at least
,,_ 100 Gb/in
2 by 2004.
This is even far outstripping
technology, which appeared to have such a bright future a serious competitor to magnetic discs for high-data-rate,
optical
recording
just a few years ago but has not become high-density storage. We believe the
VLBI community should begin to prepare now for a changeover front-runner technology for the new Haystack Mark V system.
to magnetic
discs,
which
is the
7 i i I
6
I
i
QL
5
DiscStreet 4
•
•
,,.,
;ricer
, •
.......
Disc
•
I;;G ;G.;
"J..
/
:.-,,,/ LTO,.. 0
Disc industry i
1980
=
1985
1990
T
1995
I
2000
i
2005
2010
Year
Figure 1. Disc/Tape
2.2.
The
Mark
V VLBI
A 'Mark V' VLBI Haystack Observatory. interfaces, magnetic
Data
Price Comparisons
System
data system based on magnetic disc technology is now being Based on a standard PC platform with standard commercial
designed at busses and
it will support a continuous data flow of at least 1 Gb/sec to an array of up to ,,,16 discs. The only custom hardware will be VSI-H formatter and deformatter interfaces.
Because the Mark V system is based on a standard PC platform, the data stored to discs will also be available for local analysis by the PC or for transmission over a network for e-VLBI. The cost of either the 1 Gb/sec Mark V recording or playback system (without discs) is expected to be $20K for VLBA/Maxk the same storage capacity. Disc drives will be mounted insertion/removal external handling
in carriers,
holding
either
single or multiple
Other
There
Benefits
are a number
• Rapid
of Disc-Based of other
random
• Essentially
access
instant
• Self contained;
2.5.
benefits
synchronization
expensive
tape
host
Mark
deployable
platform,
upgraded
V Development
of magnetic
discs, made for multiple
ready
Data
weight
of 12 discs containing
System
discs over magnetic
tape:
and cheapest
including
as newer
into a correlator
are not needed
the
models
'dimestore'
computer become
and
IDE disc drives,
interface
cards,
while still using
can be easily
and
available
Schedule
is now beginning the development Early demonstrations of feasibility system
the shipping
V VLBI
on playback
drives
• The
entire
unattended IV media of
to any data
buy and use the latest
Haystack technology.
276
obvious
Mark
• Can always older ones
inexpensively
so
cycles. When modern disc drives are powered down, they axe quite robust to forces and can be shipped easily in padded containers. Including the carriers,
the shipping weight per disc should be 20°/s
> 30°/s 1
Annual
Report
2
20.6 GHz 380 MHz
31.63 GHz 380 MHz
2.9°/3.4 ° -18 dB 100 ° :t:0.01 ° C
2.0°/2.3 ° -23 dB I00° +0.01 ° C
16 bit
16 bit
have
been performed
during
delay for the month
and a comparison between estimates of the wet propagation delay results inferred from the observed WVR sky brightness temperatures.
IVS
Channel
the sunl-
carried out at the Esrange Space Centre near was collocated with one of the receiving sites in
the continuously operating Swedish GPS network. Figure 3 shows the time series of derived wet propagation
2000
Space Observatory.
Azimuth
Channel Centre frequency Channel bandwidth
mer and fall 2000 Kiruna in northern
is equipped with a horn antenna, amplifier and A/D converter.
developed
part
Figure 1 shows of its control and
using
the
GPS
of August data
and
2000 the
283
OSO
Technology
Developme
m Center
Onsala
....
Space
Observatory
(OSO)
_2......
RS232
_.._---jf
Figure
1. The
new
Figure
WVR.
2.
Schematic
acquisition
As
expected
Kahnan observed tile
the
filter
software
integration
but
brightness
we
(the
estimates;
systems
contain
more
data
(see
be
higher
to
representation of the
short
Fig. than
new
term
3).
of the
and
the
data
WVR.
variations
However,
compared
we
expected
control
and
find
the
to white
modifications
the
smooth
noise
will
be
in
the
made
to
algorithms. bias are
between
error
algorithm
error
the
GPS
investigating
temperatures;
temperatures
series GPS
temperatures
is a clear
is unknown
20
time using
brightness
There
GPS
WVR
estimates
__
in the used
in the
....
the
model
WVR
at
Kiruna
used
and
the
following
to
r
WVR
algorithm was
results
possible used
(terived tile
r--T
to for
interpolate
(see
Fig.
3).
explanations: calculate the
ground
The
errors wet
Swedish
delay
west
pressure
origin
in
the
from
the
this
[)rightness
coast);
at
of
observed
error
GPS
in
the
antenna.
-
a) d15
i
>
(,9
"_10
-
5
0_
_
_
5
Figure
3.
Equivalent
surements from two
28:1
the
t
10
during new
methods
WVR GPS
zenith August
wet 2000
(green/gray and
i
0
15 20 Day of August, 2000
microwave
25
delay
derived
from
at tile
Esrange
Space
dots)
and
from
GPS
30
observations Centre (thin
'
0
with (Kiruna):
black/blue
the
new
a)
Time
line);
5 10 15 WVR wet delay at Kiruna, cm WVR
and
series
b) V_t
from
of wet delay
GPS
delay
results
20
mearesults
from
the
radiometry.
2000
IVS Annual
Report
Onsala Space 2.
Observatory
Development
(OSO)
OSO
of a New
S/X
Feed
Technology
Development
Center
System
The development of a new S- and X-band of the corrugated horn that resulted in good
feed [5], [6] is ongoing. After the successfid re-design antenna diagrams the coaxial waveguide transformer
(COWAT) was also re-designed sill(:(; its centre The re-designed COWAT was manufactured
slightly off the desired value [7]. 2000 with good cross-polarization isolation
fr('quency
was
during
(24 dB at 8.12 GHz, 38 dB at 8.62 GHz) and good return loss at X-band only -8 dB for the S-band return loss it did not reach the specifications
(-22 dB). However, with for S-band. No S-band
polarizers have been manufactured yet, so no cross-polarization data are available for S-band. Currently a re-design of the horn throat is under consideration ill order to overcome the return loss difficulties
(see Fig. 4).
The
intention
is to make
a wider
waveguide
opening
improving the return loss, 1)at without affecting the behavior at X-band. The frequency surface is supposed to let S-band through, and act as a horn wall for X-band.
at S-band, sele(:tive
Horn
Upper
S-band
coaxial
_ "
Waveguide X-band
'_'222
Circular
_
_
Waveguide Frequency
selective
..................................... Sur[ace
Z-Axis
>-./ Lower
S band
Coaxial
_ _
_ _
Waveguide
Figure
3.
4. Considered
_
re-design
of the
horn
_ _
throat
for the
new
S/X-feed
system.
Outlook
The IVS Technology Development Center at the ()nsala Space Observatory will continue with the developinent of the new radiometer and the new S/X feed system. W(; will concentrate our efforts on the software integration algorithms for tile new WVR in ord('x to ilnprove its performance. We will especially investigate the reason for the obvious bias between the radiometer results and GPS results for wet delay obtained from the measurements at Kiruna. Extensive test measurements and the results for atmospheric t)aramet('xs techniques.
will be carried out at the Onsala Space Observatory will be conq)are(t to results from the other collocated
The developlnent of the new S/X feed system will tbcus re-design of the horn throat will hoI)efiflly solve the prot)lems.
2000
IVS Annual
Report
on the
return
loss difficulties.
A
285
OSO Technology
Development
Center
Onsala Space Observatory
(()SO)
References [1] Stoew, B., and C. Rieck, Dual Channel the 13th \_brking Meeting oi1 European (eds.), 261=264, 1999.
Water Vapour Radiometer Development, In: Proceedings of VLBI for Geodesy and Astrometry, W. Schliiter and H. Hase
[2] Stoew, B., Data acquisition and software based temperature stabilization, Master's thesis, Department of Radio and Space Science, Chalmers University of Technology, GSteborg, Sweden, 1998. [3] Rieck, C., A pointing control and Space Science, Chalmers
system for a microwave radiometer, Master's thesis, Department University of Technology, GSteborg, Sweden, 2000.
[4] Stoew, B., C. Rieck, and G. Elgered, First results from a new dual-channel water vapor Ill: Proc. of the 14th Working Meeting on European VLBI for Geodesy and Astrometry, F. Mantovani and M.-A. Perez-Torres (eds.), 79 82, 2000. [5] Elgered, G., and R. Haas, Geodetic Very-Long-Baseline 1996 1997, In: Proc. of the 12th Working Meeting B. R. Pettersen (ed.), 49 53, 1997. [6] Elgered,
G, P.-S.
Kildal,
J. Flodin,
B. Hansson,
of Radio
radiometer, P. Tomasi,
Interferometry at the Onsala Space Observatory on European VLBI for Geodesy and Astrometry,
L..Pettersson,
S. Raffaelli,
J.O.
Rubios-L6pez,
and
A. Tengs, A Dual Frequency Feed System for the 20 m Radio Telescope at the Onsala Space Observatory, In: Antenn 97, Proceedings of the Nordisk antennsymposium i GSteborg, 279-287, 1997. [7] Elgered, G, R. Haas, and L. Pettersson, Space Observatory, In: International VLBI NASA/TP 1999-209243, N. R. Vandenberg
286
The IVS Technical Development Service for Geodesy and Astrometry (ed.), 272 275, 200(}.
Center at the Onsala 1999 Annual Report,
2000 IVS Annual
Report
UJi>'/
7
m
•
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