RADCAL: Precision Orbit Determination with a Commercial Grade GPS Receiver

John V. Langer, William A. Feess, Kristina M. Hanington, Michael R. Bacigalupi, Michael A. Cardoza, Richard G. Mach and P.A.M. Abusali

Abstract:	This paper represents a first report on the progress of the GPS-based orbit estimation project for the USAF Space Test and Small Launch Vehicle Program RAD- CAL radar calibration satellite. RADCAL is a small, relatively inexpensive satellite built by Defense Systems, Inc. (DSI) of McLean, Vir- ginia. Launched June 25, 1993 on a Scout rocket, its primary mission is to provide calibration data for DOD C-band radar systems worldwide. This mission requires a post-flight ephemeris accurate to 5 m in po- sition (la), available within 5 working days. As an experimental payload, RADCAL is outfitted with two non-military, CA-code, non-space-qualified commercial-grade GPS receivers. The purpose of the payload is to determine what procedures will be re- quired to enable the GPS-based system to act as a feasible backup to the principal orbit determination system. This paper reviews the pre-launch analysis and simula- tion efforts, illustrating why the various processing and tasking concepts were selected. It then compares the results of the initial processing efforts with both the initial expectations and ephemerides derived from two alternate approaches: Doppler beacon tracking and a technique based on the Differential-GPS concept. We summarize the conclusions that arise from these com- parisons and discuss future steps for improving the GPS-based estimation scheme.
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:	421 - 431
Cite this article:	Langer, John V., Feess, William A., Hanington, Kristina M., Bacigalupi, Michael R., Cardoza, Michael A., Mach, Richard G., Abusali, P.A.M., "RADCAL: Precision Orbit Determination with a Commercial Grade GPS Receiver," Proceedings of the 1994 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1994, pp. 421-431.
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