GPS Orbit Determination in the Presence of Selective Availabilty for The Extreme Ultraviolet Explorer

Kenn Gold, Angie Reichert, George Born, Willy Bertiger, Sien Wu, and Tom Yunck

Abstract:	The Extreme Ultraviolet Explorer was launched in the summer of 1992 with a single-frequency GPS receiver on-board. GPS data from this mission have been processed with Jet Propulsion Laboratory’s GIPSY- OASIS II software in a single receiver real time positioning mode. The objectives of the analysis were to determine the error sources that would affect real time on-board satellite tracking with GPS and to develop strategies to minimize those error sources. Differential solutions using full dynamic models and a global ground network provide truth orbits to determine the accuracy of those generated in the real time study. A single frequency ionosphere calibration technique is demonstrated in which the phase and pseudo-range data are averaged to remove first order ionosphere delay effects. Also in this analysis, a method known as reduced dynamic tracking is applied to lessen the effects of mismodeled satellite dynamics. In this method, stochastic acceleration parameters are estimated in each coordinate (radial, along track and cross track) to account for unmodeled acceleration. Gravity field truncation is shown to be the largest source of dynamic model error. Results are presented for tuning the level of stochastic acceleration that best recovers orbit error for different subsets of the JGM2 gravity field, with different data types, and with and without selective availability (SA) error. Orbit accuracy results from data sets corrupted by SA are compared to those from non-SA days to demonstrate the effects of dynamic smoothing of the SA clock dither error. Finally, analysis is presented in which the selected terms from the full gravity field are chosen to produce accurate orbits with the minimum required number of terms.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	1191 - 1199
Cite this article:	Gold, Kenn, Reichert, Angie, Born, George, Bertiger, Willy, Wu, Sien, Yunck, Tom, "GPS Orbit Determination in the Presence of Selective Availabilty for The Extreme Ultraviolet Explorer," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 1191-1199.
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