Flavien Mercier (CNES, France); Eva Jalabert (CNES, France); John Moyard (CNES, France); Sabine Houry (CNES, France)

The Sentinel-3A spacecraft was launched by the European Space Agency on February 16, 2016, to extend the continuous record of accurate sea surface height measurements performed on the polar Sun-synchronous orbit, begun in 1991 by the ERS mission and continued in 2002 by the Envisat mission.
Sentinel-3A, like CryoSat-2 (ESA), HY-2A (CNSA), or Saral/AltiKa (CNES/ISRO) is complementary to the other Jason operational satellites, with a higher altitude and a lower inclination. All of these missions contribute to the altimeter constellation while enhancing the global coverage, for which the CNES Precision Orbit Determination (POD) Group delivers precise and homogeneous orbit solutions.
In this paper, the overall accuracy of the Sentinel-3A GDR-E orbit solution will be evaluated through intercomparisons with external analysis centers, using different models, combinations of tracking data or parameterization techniques. We will also give an overview of the performance of all available tracking systems operating on Sentinel-3A, and address some issues concerning the prospects for improvements in modeling of the tracking data that would allow improving the accuracy of the POD solutions in the long run.