The First Low Earth Orbiter with Precise GPS Positioning: Topex/Poseidon

Willy Bertiger, Yoaz Bar-Server, Bruce Haines, Rodrigo lbanez-Meier, Ron Muellerschoen, Tim Munson, H.J. Rim, Sien Wu, Tom Yunck, P. Abusali, Bob Schutz, Pascal Willis

Abstract:	The Topex/Poseidon oceanographic satellite was launched in August 1992 carrying a high performance GPS receiver. The purpose of the receiver is to evaluate GPS for precise orbit determination of low orbiting Earth satellites. Using GPS, we have obtained an estimated radial orbit accuracy of 3 cm RMS for Topex/Poseidon, and estimated cross track and along track accuracies of better than 10 cm. To obtain this accuracy, we have used specialized filtering strategies that take advantage of the global 3- dimensional coverage provided by the GPS constellation. The particular family of filtering strategies used has come to be known as reduced dynamic tracking. In this technique a small adjustment to an arbitrary 3- dimensional acceleration is made at each measurement time to correct for mismodeled dynamics using the strength of the GPS measurement system. Since each adjustment is essentially local, the information needed to compute the adjustment must come primarily from the instantaneous measurement geometry rather than satellite dynamics. Orbit accuracy has been evaluated through such techniques as postfit measurement residuals, orbit differences between overlapping data arcs, orbit differences with traditional dynamic orbit solutions derived from different measurement systems (laser ranging and DORIS doppler) and different analysis software, and altimeter crossover statistics.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	269 - 277
Cite this article:	Bertiger, Willy, Bar-Server, Yoaz, Haines, Bruce, lbanez-Meier, Rodrigo, Muellerschoen, Ron, Munson, Tim, Rim, H.J., Wu, Sien, Yunck, Tom, Abusali, P., Schutz, Bob, Willis, Pascal, "The First Low Earth Orbiter with Precise GPS Positioning: Topex/Poseidon," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 269-277.
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