Accuracy of GPS Determined TOPEWPoseidon Orbits During Anti-Spoof Periods

Ronald J. Muellerschoen, Willy I. Bertiger, Sien C. Wu, Timothy N. Munson, James F. Zumberge and Bruce Haines

Abstract:	The Topex/Poseidon satellite carries a high precision GPS Demonstration Receiver (GPSDR). When the GPS anti-spoof function is off, the GPSDR uses P-code to obtain GPS pseudorange and carrier phase observables at Ll and L2 frequencies. These observables can be combined to yield ionospherically-free pseudorange and phase measurements. During anti-spoof periods, ttie GPSDR tracks only the Ll C/A signal. Obtaining data at one frequency prohibits the computation of ionospherically-free measurements. Combining the GPSDR flight measurements with ionospherically corrected data acquired simultaneously from a global ground network of Rogue and TurboRogue receivers and solving for stochastic clocks eliminates the effects of selective availability, as well as satellite and ground receiver clock errors. GPS data sets for two different three-day anti-spoof periods have been processed with the GIPSY-OASIS II data analysis software. The accuracy of the Topex/Poseidon orbits resulting from processing these ionospherically corrupted measurements is evaluated. A method of removing the ionosphere delay inherent in single frequency measurements is investigated. It is demonstrated that the radial accuracy of TopexiPoseidon orbits during anti-spoof periods ranges from 4 to 5 cm RMS (root mean square), and cross track and along track accuracies are better than 14 cm RMS.
Published in:	Proceedings of the 1994 National Technical Meeting of The Institute of Navigation January 24 - 26, 1994 Catamaran Resort Hotel San Diego, CA
Pages:	607 - 614
Cite this article:	Muellerschoen, Ronald J., Bertiger, Willy I., Wu, Sien C., Munson, Timothy N., Zumberge, James F., Haines, Bruce, "Accuracy of GPS Determined TOPEWPoseidon Orbits During Anti-Spoof Periods," Proceedings of the 1994 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1994, pp. 607-614.
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