Reprocessing of Envisat and Cryosat Precise oObits at CNES : Results, Implications and Prospects
Cerri, Luca; Couhert, Alexandre; Houry, Sabine

Precise DORIS and SLR-based orbits for the Envisat and Cryosat ESA missions have been recently reprocessed at CNES using models consistent with the GDR-D POD standards, named after the version-D of the Geophysical Data Record products of the Jason series of Sea Surface Topography missions. The fundamental difference between this new set of orbits and the previous one is the inclusion of GRACE-derived geopotential linear rates up to degree and order 50 to account for the long term variability of the non-tidal time varying gravity field, and the adoption of ITRF2008 as the most recent realization of the International Terrestrial Reference System.
We summarize the benefit of these new POD standards focusing on the long term stability for mean sea level applications and outline the error budget for the current reference orbit solutions. In particular, we discuss the residual modeling errors of both gravitational and surface forces, and indicate potential improvements for the new series of orbits that are currently being prepared. We also address the problem of the future stability of operational POD solutions in case potential loss of GRACE data for few years, using the DORIS-based point-mascon approach that has been recently developed at CNES.