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
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)
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) – mm 0
December 11, 2006 BJH 4 Fall AGU 2006 mm GRACE-Based Phase-Center Variation (PCV) Maps Reveal GPS Antenna Elements mm Block II/IIA PCV Block IIR-B(M) PCV mm Block IIA Antenna (Mader and Czopek, 2002) Block IIR-A PCV PCV for Ionosphere-free Carrier (LC) with Mean Offset Removed
December 11, 2006 BJH 5 Fall AGU 2006 T/P Radial Antenna Offset Explained
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 mm
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Release 07a Comparison with GDRB
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting GDRB-ITRF2000, Rel07a/GSFC-ITRF2005
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
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Geographic Radial Comparison to GDR-B mm Cycles Cycles RMS: 1.9 mm RMS: 3.5 mm ITRF Z ~ 11.5 ITRF Z ~ 5.1
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Geographic Radial Comparison to GSFC SLR+DORIS mm Cycles Cycles RMS: 2.9 mm RMS: 3.4 mm GSFC and JPL Rel07a both use ITRF2005
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Release 06b - Release 07a mm Cycles RMS: 1.8 mm
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Xover Tests
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Xover Tests
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
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Backups
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Jason Phase Simulation mm Simulation/Limitations Bus Structure -- Flat Plates Other GPS Antenna -- Disk Radiometer -- Disk Empirical 2XSimulation
December 11, 2006 BJH 18 Fall AGU 2006 GPS Transmitter PCV Maps Explain Anomalous Estimated Radial Antenna Offsets for Jason-1
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Improvements Over JPL Release 4, Nov Release 04bRelease 6.0b SLR Mean Monthly Variance (mm 2 ) 136 +/ /- 40 SLR Median Monthly RMS (mm) 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
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting R06b Comparison to GDR
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Reference Frame GDRB vs Rel07b
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting Release 06b - Release 07a Cycle Mean Z