The quality and the precision of the satellite orbit is a critical component of the OSTM mission and provides the central reference frame for the altimeter data. Over the 20-25 year time span that comprises the TOPEX/Poseidon, Jason-1, Jason-2 (OSTM), and Jason-3 missions, it is essential that the orbits be in a consistent and stable reference frame, calculated with a state of the art set of geophysical standards. By providing orbits of the highest accuracy and consistency possible, this investigation advances the OSTST goal of providing the best possible satellite-derived ocean surface topography data set. For this investigation we propose to
- investigate how to apply a consistent and sufficiently detailed model of time-variable gravity of the Earth across the TOPEX and Jason missions from 1992 to 2016;
- evaluate and characterize the error on the orbits and the altimeter data of the forward modeling of the Earth s center of mass motion, not presently included in the GDR-C or GDR-D standards;
- validate the performance of the tracking systems on Jason-3 by processing data from all tracking systems (SLR, DORIS, GPS and altimeter crossovers), and inter-compare the system performance with Jason-2 and Jason-1;
- produce a consistent set of orbits for Jason-2 & Jason-3 during the tandem phase to support the calibration of the altimeter;
- on an-ongoing basis validate the orbit POE s produced by the Jason-2 & Jason-3 missions for the project GDR's;
- test other force and measurement model improvements including : a) the application of next-generation satellite surface force models that reduce the impact of the non-conservative forces, b) updates to the tracking network terrestrial reference frame (TRF), with each new realization of the International Terrestrial Reference Frame;
- produce an updated set of orbits and geophysical standards based on the preceding analyses, and test their application not only on the Jason satellites and TOPEX, but also on Envisat/SENTINEL-3 and Cryosat-2.
The products from this investigation will include:
- Precise orbits for Jason-2 and Jason-3 on an ongoing basis and especially during the tandem calibration phase using current mission standards or easily implemented updates;
- Improved orbits for TOPEX/Poseidon and all the Jason satellites (1992 - 2016) using the best possible representation of time-variable gravity, improved surface force modeling, updated terrestrial reference frame and other improvements;
- A complete orbit modeling error budget and an assessment of its impact on short-term and long-term estimates of mean sea level change.