CoAuthors

Flavien Mercier (CNES, France); Jeroen Geeraert (University of Colorado, United States); John Moyard (CNES, France); Eva Jalabert (CNES, France); Sean Bruinsma (CNES, France); Sabine Houry (CNES, France)

Orbit-centering discrepancy between the different Jason POD analysis centers (JPL, GSFC, ESOC and CNES) has been identified as one of the main contributor to their long-term radial orbit error budget. This miscentering effect on the orbits comes from the tracking measurements. Indeed, even though satellites ideally orbit around the center-of-mass of the total Earth system (CM or geocenter), the strength of the tie to the reference network origin is dependent on the tracking technique and/or parameterization used. For example, given a displacement of the network origin from the ITRF origin, that error translates approximately 100% to the orbit using Satellite Laser Ranging (SLR) measurements, 74% using Doppler Orbit Determination and Radiopositioning Integrated by Satellite (DORIS) only measurements, and approximately 30% using GPS measurements (depending on the ambiguity fixing strategy, and relative to the reference given by the GPS orbits/clocks solution). Therefore in order to account for the miscentering, the geocenter motion could be estimated alongside the dynamic parameters of the satellite. This has already been successfully achieved using the SLR network, but the DORIS network derived geocenter motion has been reported to be noisier with larger systematic errors. Yet, due to the more numerous and better uniformly distributed DORIS stations across the globe, it could have the potential to yield competitive results, once the systematic errors are identified and mitigated, as will be shown in this paper. The obtained orbit parameterization will be tested on different altimeter satellites and the DORIS-derived geocenter motion will be compared to independent SLR-based estimates.