16. Amplitude GCCâZ [mm]. 364.0. 50.0. 69.0. 70.2. 87.0. 38.9. Period in Days. GNSS satellites only (MW+SLR): OPR free (cyan) vs. OPR fixed (brown). 117.8.
Geocenter coordinates from SLR and combined GNSSGNSS-SLR analysis D. Thaller (1), K. Sośnica So nica (1), A. Jä Jäggi (1), R. Dach (1), G. Beutler (1), M. Mareyen (2)
(1) Astronomical Institute, University of Bern, Switzerland (2) Bundesamt für Kartographie und Geodäsie, Frankfurt a.M., Germany
EGU General Assembly 2012, Vienna
Astronomical Institute University of Bern
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Overview
Geocenter from singlesingle-technique solutions: solutions: Comparison of GNSS and SLR
Geocenter from combined GNSSGNSS-SLR solutions: solutions: Impact of weighting Impact of range biases Impact of microwave antenna offsets (SAO) and laser array offsets (LRA) Impact of orbit parameterization
Conclusions
Astronomical Institute University of Bern
Weekly GNSS: CODE reprocessing using IGS08 (TRF, antenna model) Weekly SLR: Computed at AIUB, based on LAGEOS satellites 20
10 GCC−Y [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
SLRSLR-only and GNSSGNSS-only geocenter series
0
−10 GNSS: Mean = 5.2 mm, RMS = 4.4 mm SLR: Mean = 1.2 mm, RMS = 3.6 mm −20 2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
Comparable series from GNSS and SLR (except (except for shift: shift: 4 mm) Astronomical Institute University of Bern
40
GCC−Z [mm]
20
0
−20 GNSS: Mean = 5.9 mm, RMS = 10.7 mm SLR: Mean = 0.2 mm, RMS = 6.4 mm −40 2000 ∆ GCC−Z [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
SLRSLR-only and GNSSGNSS-only geocenter series
40 20 0 −20 −40 2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
∆ Z: Mean = −5.7 mm, RMS = 12.6 mm
2001
2002
2003
2004
2005
2006
2007
2008
2009
SLR shows clearly fewer variations than GNSS Astronomical Institute University of Bern
2010
2011
GNSS−only (blue) vs. SLR−only (orange) 6 50.0 117.8
5
GCC−Z amplitude [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
SLRSLR-only and GNSSGNSS-only geocenter series
70.2
364.0
4
333.7
3 166.8
2
GNSS-only 7-day solutions SLR-only 7-day solutions
222.4
182.0 1 0 0
50
100
150 200 250 Period in Days
300
350
400
Draconitic year is clearly visible: GNSS = 352 d, d, LAGLAG-2 = 222 d
Annual and draconitic signal are not distinguishable for GNSS
Big amplitudes at harmonics of draconitic year for GNSS Astronomical Institute University of Bern
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Combined GNSSGNSS-SLR solutions
Microwave observations to GPS / GLONASS
SLR observations to GPS / GLONASS
SLR observations to LAGEOS
Connection of SLR and GNSS at the GPS / GLONASS satellites ( „satellite coco-location“ location“ )
No local ties applied
Astronomical Institute University of Bern
GNSS F7 (blue) vs. GNSS+SLR A73 (pink) 7 50.0
GNSS-only 7-day Combined GNSS-SLR 7-day
6 GCC−Z amplitude [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Combined geocenter
117.8
5 70.2 4
333.7 69.0
3
364.0
114.4
2 1 0 0
50
100
150
200 Period in Days
250
300
Annual signal remains; draconitic GNSS signal vanishes
Harmonics of draconitic GNSS year are reduced but not eliminated
350
Astronomical Institute University of Bern
400
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Combined geocenter: geocenter: Impact of weighting σ SLR_LAG
σ SLR@GNSS
Mean
σ GNSS
σ GNSS
X
Y
Z
X
Y
Z
A
1
1
3.7
4.9
5.0
3.9
5.0
7.6
B
10
10
3.7
4.9
3.8
3.9
4.9
7.9
C
0.1
0.1
4.1
4.8
6.8
4.9
5.8
11.7
D
1
10
4.2
5.0
3.8
4.3
5.4
8.2
GNSSGNSS-only series
4.6
5.2
5.9
3.5
4.4
10.7
SLRSLR-only series
1.0
1.2
0.2
4.1
3.6
6.4
RMS
Higher weight for SLR data (solution C) degrades the solution All other combinations show improvement w.r.t. GNSS-only Down-weighting SLR@GNSS data (B B or D) not necessarily needed Astronomical Institute University of Bern
Considering / Ignoring range biases (per Sta, per Sat): Impact on geocenter 20
∆ X: Mean = 0.1 mm ∆ Y: Mean = −0.3 mm ∆ Z: Mean = 2.5 mm
15
∆ GCC [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Combined geocenter: geocenter: Impact of RGB
10 5 0 −5 2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
Comb 1: No range bias considered Comb 2: Range bias per station, per satellite considered ⇒ Bias and annual signal (mainly in z-component): several mm Astronomical Institute University of Bern
2011
Considering / Ignoring corrections to SAO, LRA (RGB applied): Impact on geocenter 1 0
∆ GCC [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Combined geocenter: geocenter: Impact of SAO, LRA
−1 −2 −3 ∆ X: Mean = −0.7 mm ∆ Y: Mean = −0.1 mm ∆ Z: Mean = −1.8 mm
−4 −5 2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
Comb 1: Range bias per station, per satellite considered Comb 2: RGB, SAO, LRA corrections considered ⇒ Bias at mm-level (mainly in z-component) Astronomical Institute University of Bern
2010
2011
GNSS satellites only: only: Test
solution: solution: OPR parameters D, Y, X un-constrained
«Standard» Standard»
solution due to correlations with geocenter: Onceper-Rev (OPR) parameters D, Y fixed GNSS satellites only (MW+SLR): OPR free (cyan) vs. OPR fixed (brown) 16 364.0
50.0 14 12 Amplitude GCC−Z [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Impact of orbit constraints
69.0
10 8
70.2 6
87.0
38.9 58.0
4
117.8
182.0 333.7
2 0 0
50
100
150
200 Period in Days
250
300
350
Astronomical Institute University of Bern
400
Combined GNSSGNSS-SLR solution: solution: OPR parameters unun-constrained GNSS satellites only Combined GNSS+SLR (including (including LAGEOS satellites) satellites) OPR free: GNSS−Sat−only (a73r6, blue) vs. GNSS−Sat + LAGEOS (A73R6, orange) 16 364.0
50.0 14 12 Amplitude GCC−Z [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Impact of orbit constraints
69.0
10 8
70.2 6
87.0
38.9
182.0
4 2 0 0
50
100
150
200 Period in Days
250
300
Astronomical Institute University of Bern
350
400
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Conclusions
SLR geocenter series are very clean for all 3 components
GNSS geocenter series for X-, Y-component are very clean
GNSS geocenter series for Z-component shows artifacts at periods related to the draconitic year
These artifacts are reduced in combined GNSSGNSS-SLR solutions, but 3rd, 5th, 7th harmonics are still present
Ignoring range biases and antenna offset corrections generates a shift and annual variations in Z-component of ~4 mm (partly also in Y-component)
The negative impact of OPR parameters on geocenter cannot be fully avoided by the inclusion of SLR data
Astronomical Institute University of Bern
10
∆ X (shifted +5): Mean = 0.1 mm
5
∆ GCC [mm]
D. Thaller et al.: Geocenter coordinates from SLR and combined GNSS-SLR analysis EGU General Assembly 2012, Vienna
Impact of atmospheric loading
∆ Y (not shifted): Mean = −0.1 mm 0
−5 ∆ Z (shifted −5): Mean = 0.2 mm −10 2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
⇒ See poster presentation by Sośnica et al.: Impact of atmospheric loading corrections on SLR and the consistency between GNSS and SLR solutions. Session G2.1, Thursday Astronomical Institute University of Bern
2011