DORIS based precise orbit and reference frame determination using multiple altimetry satellite missions

The German Research Centre for Geosciences (GFZ) is one of the Associate Analysis Centers (AAC) of the International Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) Service (IDS).In the framework of a future contribution to the DORIS part of the International Terrestrial Reference Frame (ITRF) a repertoire of well-known satellite altimetry missions equipped with DORIS receiver, in particular Topex, Envisat, Jason-1/2, Cryosat-2, Saral, Jason-3, Sentinel-3A/B and Sentinel-6A Michael Freilich, have been processed.Therefore, Precise Orbit Determination (POD) is performed for these missions, and orbits are generated based on DORIS-only and on the combination of DORIS and Satellite Laser Raging (SLR) observations.The quality of the orbits is subsequentely analyzed internally and in comparison with external orbit solutions.For external comparisons, the combined orbit solutions of the Copernicus POD quality working group (CPOD-QWG), which is assumed to have superior absolute accuracy and minimal residual systematic errors, are used for the Sentinel missions, while for the remaining missions orbit products by Centre National D’Etudes Spatiales (CNES) are used.Eventually, starting from the DORIS only solutions, weekly local terrestrial reference frames (TRFs), are computed for each single satellites, as well as a combined solution for the entire analysis interval with all satellite missions is generated.The TRF solutions thus generated are evaluated with respect to the reference frame defining parameters, i.e. origin, scale, and orientation, in comparison to the a piori TRF.