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Ocean Surface Topography from Space
Calibration and Validation of the Precise Orbits for OSTM-Extending the TOPEX, Jason-1
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Frank Lemoine
(NASA/Goddard Space Flight Center)

Brian Beckley
(SGT, Inc.)
Scott Luthcke
(University of Colorado at Boulder)
Nikita Zelensky
(SGT, Inc.)


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. The analysis of OSTM altimeter data and data from TOPEX/Poseidon and Jason-1 requires that the orbits for all three missions be in a consistent reference frame, and calculated with the best possible standards to minimize error and maximize the data return from the 15+ year time series, particularly with respect to the demanding application of measuring mean sea level change. For OSTM, we will (1) validate the performance of the tracking systems on OSTM, by processing data from all available tracking systems on the spacecraft (SLR, DORIS, GPS, and altimeter crossovers), and intercomparing the resultant orbits internally and with external POD analysis centers; (2) Produce a consistent set of orbits for Jason-1 and OSTM during the tandem phase in order to facilitate the calibration of the altimeter; (3) On an on-going basis following the tandem phase validate the orbit POE's produced by the OSTM project; (4) Test model improvements in view of continuing to improve the quality of the entire time series of orbits for TOPEX/Poseidon, Jason-1 and OSTM, by taking advantage of improvements to the nonconservative force models for these satellites, investigating other force and measurement model improvements, and testing and validating the performance of the tracking stations and the terrestrial reference frame from which the tracking station coordinates and velocities are derived. The products from this investigation will include: (1) Precise orbits for both Jason-1 and OSTM during the tandem mission phase consistent with the ITRF2005 orbits of Beckley et al. (2007); (2) Improved orbits for, TOPEX/Poseidon, Jason-1 and OSTM, using the modeling improvements necessary to produce a consistent and accurate orbit time series for the OSTST.

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