Considerations for The Application of GPS in Satellites: GPS System Trade Study

James Kronman and Thomas McElroy

Abstract:	The use of a Global Positioning System (GPS) re- ceiver onboard low Earth orbit (LEO) satellites has been demonstrated for high accuracy orbit determination (OD). Geosynchronous (GEO) and highly elliptical or- bit (HEO) satellites also can benefit from the applica- tion of GPS technology but there are unique considera- tions in these implementations. The LEO mission, dis- cussed in this paper as a point of reference, has been implemented on several space missions. The LEO mis- sion has the benefit of simultaneous visibility of at least four GPS vehicles at all times. Measuring the user satellite position relative to four GPS satellites will enable the user to estimate his instantaneous posi- tion and time. Autonomous navigation for the GE0 mission becomes more difficult due to visibility limita- tions. Architectures are considered that employ either onboard or ground-based GPS receivers; the onboard re- ceiver option is further divided into onboard and ground- based data processing. GE0 GPS visibility and link budget drive the GE0 architecture to include a direc- tional antenna. The HE0 reference mission is a Molniya-like communications satellite in a highly ellip- tical orbit and was selected because of its interesting or- bit characteristics. This HE0 mission can be considered as a hybrid of the LEO and GE0 missions. The dynam- ics of this orbit is such that it “looks” like a GE0 mis- sion most of the time; all of the considerations of the GE0 mission apply. This paper considers a spectrum of approaches for the exploitation of GPS capabilities in space, describing each implementation approach and dis- cussing the factors to be considered in the tradeoff analy- ses for each specific application.
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:	1685 - 1692
Cite this article:	Kronman, James, McElroy, Thomas, "Considerations for The Application of GPS in Satellites: GPS System Trade Study," 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. 1685-1692.
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