A new, Linux-based control system, based on the 12m ... running on Linux-based x86 hardware. Its major .... are dedicated to sub-mm wavelengths at the SMT).
Recent Developments at the Arizona Radio Observatory T. W. Folkers, H. A. Fagg, W. A. Peters, B. Vila-Vilaro, D. C. Forbes, R.W. Freund. L. M. Ziurys Enhanced Receiver Capabilities
Introduction
New dual-channel, SSB, High Stability SIS receivers at 1.3 and 2 mm for the SMT The The receivers receivers are are in in the the process process of of being being replaced replaced at at the the SMT. SMT. A A new new 1-2 1-2 mm mm SIS SIS receiver, receiver, which which isisdual dual polarization polarization and and single single sideband, sideband, isis near near completion. completion. This This system system covers covers the the frequency frequency range range from from 130 130 -- 300 300 GHz GHz with with two two sets sets of of mixers, mixers, several several which which are are tunerless. tunerless. These These receivers receivers will will have have high high stability stabilityfor for long long integrations. integrations. Image Image rejection rejection isis achieved achieved by byreceiver receiver tuning tuning at at 22 mm mm and and by byuse use of of aa Martin-Puplett Martin-Puplett interferometer interferometer at at 11 mm. mm. All All four four mixers mixers are are in in aa single single dewar, dewar, which which isis cooled cooled by byaa Joule-Thompson Joule-Thompson closed closed cycle cycle refrigerator refrigerator system. system. Switching Switching between between frequency frequencybands bands isis readily readilyaccomplished accomplished by byrotation rotation of of the the optics. optics. A A dual dual channel, channel, single single sideband sideband 0.8 0.8 mm mm receiver receiver isis under under construction, construction, which which has has similar similar features features to to those those of of the the 1-2 1-2 mm mm system. system. This This system system isis in in aa separate separate dewar, dewar, which which has has additional additional space space available available for for aa set set of of 490 490 and and 660 660 GHz GHz mixers. mixers.
Intensity (K)
New New technical technical developments developments are are in in progress progress at at the the Arizona Arizona Radio Radio Observatory. Observatory. This This facility facility consists consists of of the the Sub-millimeter Sub-millimeter Telescope Telescope (SMT), (SMT), located located on on Mt. Mt. Graham, Graham, Arizona, Arizona, and and the the Kitt Kitt Peak Peak 12m 12m antenna. antenna. At At the the SMT, SMT, aa new new dual dual channel, channel, single-side single-side band band 120-300 120-300 GHz GHz receiver receiver has has been been installed, installed, along along with with aa newly-constructed newly-constructed 2048 2048 channel channel 11 MHz MHz filter filter bank. bank. In In addition, addition, aa 7-beam 7-beam 345 345 GHz array receiver, DesertStar, will go into routine operation on the SMT in GHz array receiver, DesertStar, will go into routine operation on the SMT in January January 2005. 2005. Both Both the the SMT SMT and and the the 12m 12m can can be be used used in in “remote “remote observing” observing” mode mode from from virtually virtually any any location. location. A A new, new, Linux-based Linux-based control control system, system, based based on on the the 12m 12m model, model, has has recently recently been been installed installed at at the the SMT. SMT. The The KP KP 12m 12m is is also also unique unique in in that that itit continuously continuously covers covers the the frequency frequency range range 65-180 65-180 GHz. GHz. Current Current status status of of these these improvements improvements will will be be presented. presented.
SMT Control System Upgrade A A new new fully fully functional functional control control system system has has been been installed installed on on the the SMT SMT Features Features include include parallel parallel processing, processing, improved improved efficiency efficiency and and remote remote observing observing In In the the spring spring of of 2001, 2001, the the staff staff of of the the ARO ARO began began the the task task of of replacing replacing the the outdated outdated control control system system of of the the SMT. SMT. The The old old antenna antenna control control system system was was based based on on aa single single VAX VAX computer computer interfaced interfaced to to the the antenna antenna control control hardware hardware and and spectral spectral line line backends backends mainly mainlythrough through CAMAC CAMAC electronics electronics packages. packages. The The CAMAC CAMAC electronics electronics was was obsolete, obsolete, difficult difficult to to maintain, maintain, and and was was increasingly increasinglyunreliable. unreliable. The The VAX VAX control control computer computer was was also also dated, dated, but but couldn't couldn't be be replaced replaced since since the the CAMAC CAMAC electronics electronics interface interface requires requires aa Q-bus Q-bus machine machine (which (which are are no no longer longer made). made). The The primary primarygoal goal was was to to completely completelyreplace replace the the old old CAMAC/VAX CAMAC/VAX control control system system with with modern modern hardware hardware and and utilize utilize State State of of the the Art Art operating operating system system technology. technology. The The new new control control system system was was modeled modeled after after the the one one developed developed by bythe the NRAO NRAOfor for use use on on the the Kitt Kitt Peak Peak 12 12 Meter Meter Radio Radio Telescope, Telescope, with with the the most most critical critical components components running running on on Linux-based Linux-based x86 x86 hardware. hardware. Its Its major majorfeatures features include include use use of of parallel parallel processing processing to to carry carryout out observing observing tasks, tasks, which which greatly greatlyincreases increases the the operating operating efficiency; efficiency; use use of of modern modern independent independent hardware hardware that that isis easily easilyupgraded; upgraded; and and the the option option of of remote remote observing. observing. The The new new control control system system has has been been in in place placeand and operational operational since since November November 2002. 2002. ItIt has has already alreadydecreased decreased dead dead time time by byaa factor factor of of two two in in regular regular observing observing modes modes (position/beam (position/beam switching) switching) and and has has increased increased the the data data rate rate for for on-the-fly on-the-flymapping mapping by byaa factor factor of of 20. 20.
∆F (MHz)
Figure 6: The new JT receiver installed at the SMT.
Figure 7: Spectrum of the 12CO(2->1) transition taken toward the Egg Nebula using the New JT Receiver.
Figure 9: The inside of the 1-2mm receiver showing 4 of the inserts attached to the “spider”, which is connected to the 4-K station.
Figure 1: (left) Block diagram of the control system at the SMT showing the interface between the receivers, backends, telescope control and data monitoring systems. (right) A block diagram of the “Tracker/Servo” part of the control system, which displays the interface of the encoders, motor drives and the control computer. These diagrams illustrate the fully distributed nature of the control system, where each task is controlled by a separate computer process allowing for asynchronous operation.
Figure 8: Expanded view of the optics for the 1-2mm receiver showing several of the polarizing grids and the Martin-Puplett interferometer used for image rejection.
Figure 10: Screenshot of the tuning interface for the new JT receiver. All aspects of the receivers tuning are remotely controllable using this interface.
7 Pixel DesertSTAR & 64 Pixel SuperCam 345 GHZ Heterodyne Array Receivers 7 Pixel DesertSTAR
Remote Observing
64 Pixel SuperCam Large Scale Submm & THZ Line Surveys One tantalizing prospect resulting from the development of large format heterodyne array receivers in the submillimeter and THz regimes is the possibility of conducting extensive interstellar spectral line surveys of the Galaxy. For example, our understanding of molecular cloud evolution would be greatly improved by surveys of highJ transition CO lines and their isotopes which are most sensitive to warm, low-opacity, high velocity gas such as that produced by outflows, photo dissociation regions (PDRs), and shocks. The angular coverage required for such a comprehensive survey underlines the need for spectroscopic imaging arrays. SuperCam, a 64 pixel 870 µm heterodyne array for the SMT on Mt. Graham, is designed to fill this need. It will perform large scale surveys in both 12CO(3->2) and 13CO(3->2) of the Galactic plane as seen from Arizona (0 < l < 240°). Taking Galactic Plane visibility limitations into account, we will use a total of 4 months of dedicated observing time over two years to perform the base-line survey; year #1 of observing will be devoted to 12CO(3->2) mapping, and year #2 will be dedicated to 13CO(3->2) mapping with follow-up spectroscopy in HCO+(4->3), for example.
With With the the completion completion of of the the new new control control system system on on the the SMT SMT 10 10 Meter Meter telescope, telescope, ARO ARO can can now now offer offer remote remote observing observing to to the the radio radio astronomy astronomy community community using using both both telescopes. telescopes. The The 10 10 Meter Meter now now joins joins the the 12 12 Meter’s Meter’s rich rich history history of of providing providing world world class class remote remote observing. observing. Astronomers Astronomers from from anywhere anywhere in in the the world world can can observe observe using using either either telescope telescope and and enjoy enjoy all all the the tools tools and and information information historically historically available available only only on on site. site. Figure 3: New control system and monitoring stations in operation at the SMT 10 meter telescope. Figure 11: DesertSTAR mounted on the SMT
New Spectrometer Backend A A new new 2048 2048 Channel Channel 11 MHz MHz filterbank filterbank for for the the SMT SMT 10-meter 10-meter Figure 13: The Power of Large Format Array Receivers:
A A new new filterbank filterbank spectrometer spectrometer for for the the SMT SMT is is in in the the final final stages stages of of testing. testing. This This instrument instrument has has aa total total of of 2048 2048 channels channels of of 11 MHz MHz resolution, resolution, steerable steerable in in groups groups of of 256 256 channels channels to to any any one one of of 88 receiver receiver inputs inputs and and to to any any segment segment of of the the 4-6 4-6 GHz GHz IF. IF. The The instrument instrument uses uses modern modern surface-mount surface-mount technology technology and and is is built built on on Eurocards.. Eurocards.. Calibration Calibration and and IF IF leveling leveling are are automatic. automatic. When When complete, complete, the the instrument instrument will will occupy occupy three three standard standard 19 19 inch inch racks. racks. The The completed completed system system should should be be at at the the telescope telescope by by February February 2005. 2005. An An additional additional 512 512 channels channels of of 250KHz 250KHz bandwidth bandwidth are are being being constructed. constructed.
As an example of how large receiver arrays will revolutionize astronomy in the FIR and submillimeter, SuperCam, a 64 pixel heterodyne array for the SMT, will be capable of performing a definitive chemical and kinematic survey of star forming clouds in 12CO(3->2) & 13CO(3->2) over 500 square degrees (12CO) of the sky in 33 full days of observing per spectral line. A corresponding survey with contemporary single pixel receivers would take over 6 years each to accomplish.
Figure 12: First multipixel light of DesertSTAR from the Orion Molecular Cloud. The 10’ x 10’ OTF map was performed in 1 hour.
Figure 14: Optical system matching SuperCam to the SMT.
Figure 4: Filterbank system being assembled and tested in the downtown lab by Project Engineer David Forbes
Figure 5: Filterbank card for the new filter bank system. The card holds 32 bandpass filters, square-law detectors, integrators and multiplexers.
Figure 15: This shows the 64 beams of SuperCam overlaid on the Horsehead Nebula. Each beam will measure a highresolution spectrum, a small segment of which is presented in the inset.
The Arizona Radio Observatory (ARO) owns and operates two radio telescopes in southern Arizona: The former NRAO 12 Meter Telescope located 50 miles southwest of Tucson on Kitt Peak and the Submillimeter Telescope located on Mt. Graham near Safford, Arizona. Combined, the two telescopes routinely cover the entire millimeter and submillimeter windows from about 4.6 mm to about 0.6 mm, and at the SMT observations can be made all the way to 0.3 mm with PI instruments. The telescopes are operated around-the-clock for about 9 to 10 months per year for a combined 10,000 hours per observing season (about 1500 hours are dedicated to sub-mm wavelengths at the SMT). The ARO offices are centrally located in the Steward Observatory building on the campus of the University of Arizona in Tucson Arizona. Additional funding for the 12 Meter is provided by the Research Corporation. Web Site: http://aro.as.arizona.edu/
