GNSS satellites as co-locations for a combined GNSS and SLR analysis D. Thaller 1), K. Sośnica 1), R. Dach 1), A. Jäggi 1), M. Mareyen 2), B. Richter 2), G. Beutler 1) (1) Astronomical Institute, University of Bern (AIUB), Switzerland (2) Bundesamt für Kartographie und Geodäsie (BKG), Frankfurt / Main, Germany
Overview 1. Satellite co-location of GNSS and SLR 2. Results from combining GNSS microwave data and SLR data to GNSS satellites, Lageos and Etalon: - GNSS-SLR range bias parameters - Offsets of Laser Reflector Array (LRA) - GNSS Satellite Antenna Offsets (SAO) 3. Conclusions
Co-locations for GNSS and SLR Co-location at GNSS satellites = Transmitting point for GNSS Reflecting point for SLR (target) Estimation of common orbit parameters Vectors of GNSS and SLR reference points w.r.t. satellite CoM needed Space Tie = Microwave part: - Antenna Offsets (SAO) w.r.t. CoM - Phase Center Variations (PCV) SLR part: Offsets for Laser Retroreflector Array (LRA) w.r.t. CoM
Combined GNSS-SLR analysis Combined analysis: GNSS microwave data + SLR range data to GNSS satellites (GPS, GLONASS) + SLR observations to Lageos, Etalon ( stable station coordinates; no range biases for most stations) Bernese Software for microwave and SLR data analysis GNSS satellites: Lageos, Etalon: 1-day orbital arcs 7-day orbital arcs Time span of observations considered: 2006.0 2011.0 5 years of data Generating a multi-year solution NNR+NNT condition for GNSS sub-network w.r.t. IGS05 no Local Ties applied (only satellite co-location used)
GNSS-SLR "range" bias LRA offset Solutions to be tested Solution 1 Solution 2 Solution 3 Solution 4 1 parameter 1 parameter 1 parameter 1 parameter per station per station per station per station Microwave SAO z- component all GNSS-SLR discrepancies might show up in range bias parameters
GNSS-SLR "range" bias LRA offset Solutions to be tested Solution 1 Solution 2 Solution 3 Solution 4 1 parameter 1 parameter 1 parameter 1 parameter per station per station per station per station Microwave SAO z- component SAO errors might show up in SLR-related parameters
GNSS-SLR "range" bias LRA offset Solutions to be tested Solution 1 Solution 2 Solution 3 Solution 4 1 parameter 1 parameter 1 parameter 1 parameter per station per station per station per station Microwave SAO z- component LRA errors might show up in range bias parameters
GNSS-SLR "range" bias LRA offset Solutions to be tested Solution 1 Solution 2 Solution 3 Solution 4 1 parameter 1 parameter 1 parameter 1 parameter per station per station per station per station Microwave SAO z- component Parameters for all error sources separately. BUT: Correlations?
SLR-GNSS range biases 50 40 30 SLR GNSS range biases per station (SAO fix) LRA fix LRA Z Std.Dev [0.1mm] Microwave SAO SLR GNSS range bias [mm] 20 10 0 10 20 30 40 50 7080 7090 7105 7110 7124 7237 7249 7308 7358 7405 7406 7501 7810 7821 7824 7825 7832 7838 7839 7840 7841 7845 7941 8834 1824 1864 1868 1873 1879 Common estimation of: LRA Offset (z-direction) GNSS-SLR range biases - Smaller range biases - Less systematic
SLR-GNSS range biases 70 60 50 40 30 20 10 0 Difference in SLR GNSS range biases (per station) (SAO ) w.r.t. "LRA " LRA Z Std.Dev [0.1mm] SLR GNSS range bias [mm] 10 7080 7090 7105 7110 7124 7237 7249 7308 7358 7405 7406 7501 7810 7821 7824 7825 7832 7838 7839 7840 7841 7845 7941 8834 1824 1864 1868 1873 1879 GNSS-SLR bias is rather an LRA offset than an SLR range bias: Approx. 25 mm
50 40 SLR-GNSS range biases SLR GNSS range biases per station (LRA fix) SAO fix SAO Z Std.Dev [0.1mm] 30 20 10 0 10 20 SLR GNSS range bias [mm] LRA offsets 30 40 50 7080 7090 7105 7110 7124 7237 7249 7308 7358 7405 7406 7501 7810 7821 7824 7825 7832 7838 7839 7840 7841 7845 7941 8834 1824 1864 1868 1873 1879 Common estimation of: GNSS Satellite Antenna Offset (z-direction) GNSS-SLR range bias parameters
SLR GNSS range bias [mm] 30 20 10 0 10 SLR-GNSS range biases Difference in SLR GNSS range biases (per station) (LRA ) w.r.t. "SAO " SAO Z Std.Dev [0.1mm] Mean diff. Median diff. = 0.9 mm = 0.4 mm 20 7080 7090 7105 7110 7124 7237 7249 7308 7358 7405 7406 7501 7810 7821 7824 7825 7832 7838 7839 7840 7841 7845 7941 8834 1824 1864 1868 1873 1879 Common estimation of: GNSS Satellite Antenna Offset (z-direction) GNSS-SLR range bias parameters Is possible errors in SAO do not map into SLR range bias parameters
50 40 30 SLR-GNSS range biases SLR GNSS range biases per station SAO fix, LRA fix SAO fix, LRA Z SAO Z, LRA Z Std.Dev [0.1mm] 20 10 0 10 20 SLR GNSS range bias [mm] 30 40 50 7080 7090 7105 7110 7124 7237 7249 7308 7358 7405 7406 7501 7810 7821 7824 7825 7832 7838 7839 7840 7841 7845 7941 8834 1824 1864 1868 1873 1879 Common estimation of: GNSS Satellite Antenna Offset (z-direction) LRA offset (z-direction) GNSS-SLR range biases
3 SLR-GNSS range biases Difference in SLR GNSS range biases per station w.r.t. "SAO, LRA Z " SLR GNSS range bias [mm] 2 1 0 1 2 3 4 5 SAO Z, LRA Z Std.Dev [mm] 7080 7090 7105 7110 7124 7237 7249 7308 7358 7405 7406 7501 7810 7821 7824 7825 7832 7838 7839 7840 7841 7845 7941 8834 1824 1864 1868 1873 1879 Mean diff. = 0.1 mm Median diff. = 0.0 mm Common estimation of: GNSS Satellite Antenna Offset (z-direction) LRA offset (z-direction) GNSS-SLR range biases Feasible!
LRA offset corrections 80 70 60 LRA z offset correction (filled = tracked by all sites) SAO SAO Z Mean correction: LRA Z [mm] 50 40 30 20 SAO SAO-Z GPS GLONASS 34.76 mm 33.56 mm 34.83 mm 26.52 mm 10 0 10 5 10 15 20 25 30 35 Satellite PRN (GLONASS = PRN + 10) Filled signatures: Satellites tracked by all SLR sites Others: Satellites tracked only by Herstmonceux (since Dec. 2009) Difference 0.06 mm 7.04 mm Significant corrections to LRA offsets Common estimation with SAO corrections is possible
SAO Z [mm] 400 300 200 100 0 100 200 GNSS SAO corrections Satellite antenna offset correction: Z component LRA LRA Z Significant corrections to SAO of igs05.atx Common estimation with LRA corrections is possible 300 400 0 10 20 30 40 50 60 70 Satellite PRN (GLONASS = PRN + 40) Mean correction: GPS GLONASS LRA 23.34 mm -142.35 mm LRA-Z 25.93 mm -138.80 mm Difference 2.59 mm 3.55 mm
Conclusions - Combination of GNSS and SLR using satellite co-location works properly - Connection via space ties is possible (without local ties) BUT: Accurate ties (in space and on sites) required for combination - Scale from SLR can be transferred to GNSS allows the estimation of GNSS satellite antenna offsets - GNSS SAOs from igs05.atx do not fit to the SLR scale - LRA offsets show significant discrepancies (~35 mm) - Separation of SLR range biases, LRA offsets and GNSS SAO is feasible