1. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting GPS-Based Precise Orbit Determination: Jason-1 Status Willy Bertiger, Bruce Haines, Shailen Desai Jet Propulsion Laboratory, California Inst. of Tech., Pasadena CA Pascal Willis Institut Geographique National/Institut de Physique du Globe de Paris, France March, 2007 Ocean Surface Topography Science Team Meeting Hobart, Australia

2. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Better Understanding of GPS Phase Centers based on GRACE Dynamics and Calibrations JEM03 – GRACE Static Gravity Field (vs GGM02C) –AOD1B Release 4 ( vs none ) Sub-daily density variations in atmosphere, gravitational effect ITRF2005 (vs ITRF2000) Release 07a Incremetal Changes Relative to Release 06b (March 2006)

3. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting GRACE As An Antenna Instrument For GPS Trans. Calibration Daily precise orbit solutions spanning two years (2004–06) One s/c at a time Dynamical POD to preserve link between scale and GM –C D and 1 cpr acc. reset every rev. per UT/CSR approach GPS ephemeris and clock offsets fixed to precise values (JPL/IGSAC) GRACE antenna a priori PCV model from anechoic chamber: 30-sec GPS data –Carrier (LC) only and carrier + code (LC + PC) solutions performed. No Z apriori Postfit residuals binned according to az/el of transmitters. –Least-squares fit to antenna map –Iterate until converged (12XLC, 5XLC/PC) –15 0 15 mm 0

4. December 11, 2006 BJH 4 Fall AGU 2006 mm -10 +10 GRACE-Based Phase-Center Variation (PCV) Maps Reveal GPS Antenna Elements -12 +18 mm Block II/IIA PCV Block IIR-B(M) PCV -10 +10 mm Block IIA Antenna (Mader and Czopek, 2002) Block IIR-A PCV PCV for Ionosphere-free Carrier (LC) with Mean Offset Removed

5. December 11, 2006 BJH 5 Fall AGU 2006 T/P Radial Antenna Offset Explained

6. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting JASON Calibration (3 Iterations) Dynamic JASON runs 2002-JAN-14 to 2006-JAN-01 Very similar in appearance to release 06b (last year) Phase Code -400400-3030 mm

7. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Release 07a Comparison with GDRB

8. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting GDRB-ITRF2000, Rel07a/GSFC-ITRF2005

9. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Reference Frame, Differences with GSFC SLR/DORIS Model Errors, GPS? Some Pattern with GDRB

10. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Geographic Radial Comparison to GDR-B -16160 mm Cycles 21-39 Cycles 150-169 RMS: 1.9 mm RMS: 3.5 mm -16 16 0 ITRF2000 - 05 Z ~ 11.5 ITRF2000 - 05 Z ~ 5.1

11. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Geographic Radial Comparison to GSFC SLR+DORIS -16160 mm Cycles 21-39 Cycles 150-169 RMS: 2.9 mm RMS: 3.4 mm -16160 GSFC and JPL Rel07a both use ITRF2005

12. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Release 06b - Release 07a mm Cycles 141-146 RMS: 1.8 mm -16160

13. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Xover Tests

14. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Xover Tests

15. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Summary Incremental Changes to JPL GPS orbits –Gravity Field, Phase Centers, AOD1B, ITRF2005 Comparison with GDR-B –Close Performance Measured by crossovers –Slightly better comparison to R06b, Z shift ITRF2005 Reference Frame Issues ~ cm (Comparison with GSFC SLR/DORIS) –Antenna, Force Models? Future Enhancements –Use Solar Panel Quaternions to improve solar pressure –Test other gravity fields, apply time varying solid earth gravity ( fit to monthly fields ) –Improved Albedo Models –Re-tune POD strategy

16. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Backups

17. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Jason Phase Simulation -30+30 mm -30 +30 Simulation/Limitations Bus Structure -- Flat Plates Other GPS Antenna -- Disk Radiometer -- Disk Empirical 2XSimulation

18. December 11, 2006 BJH 18 Fall AGU 2006 GPS Transmitter PCV Maps Explain Anomalous Estimated Radial Antenna Offsets for Jason-1

19. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Improvements Over JPL Release 4, Nov. 2005 Release 04bRelease 6.0b SLR Mean Monthly Variance (mm 2 ) 136 +/- 46125 +/- 40 SLR Median Monthly RMS (mm) 11.210.7 Residuals65% have smaller monthly residuals Mean of Daily Radial RMS ( Dynamic – Reduced Dyn) (mm) 10.1 (1376 days)9.1 (1374 days) Improved Antenna, Force Models => Re-tune Stochastics, Data weight, Outlier Detection

20. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting R06b Comparison to GDR

21. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Reference Frame GDRB vs Rel07b

22. Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Release 06b - Release 07a Cycle Mean Z