Communication Satellite Augmented GPS

Barry Siegal, Prem K. Munjal, Robert Sung and Mohan Ananda

Abstract:	This paper presents a concept for transmitting GPS signals through a communication satellite primarily to provide integrity status of all GPS satellites to all users, as well as to increase the number of GPS satellites for user navigation and to improve the navigation accuracy for military users. The proposed system uses modified satellites of the currently existing Defense Satellite Communications System (DSCS) in geostationary orbit. Between 1995-2000, it is expected that at least five DSCS satellites would be launched and it is proposed that the CAG payload be integrated with such satellites. The system assumes the GPS navigation payload to be split into two parts: (1) the space segment payload and (2) the ground segment payload. The space segment payload would be integrated with the DSCS satellite and the ground segment payload would be interfaced with the space segment payload through a DSCS terminal. The ground segment payload would generate the GPS signals with proper data modulation and uplink the signal on X- band to the space segment payload, which in turn would downlink both an X-band signal and the GPS signals on the L-band. The proposed CAG system would be totally integrated into GPS system operation. This paper presents the results of a study conducted by The Aerospace Corporation in support of the GPS Joint Program Office (JPO). The study was conducted to provide a preliminary system concept and a strawman design. A joint 6-month study is being conducted by the GPS and DSCS programs. The DSCS satellite contractor, Martin Marietta, is evaluating the impact of incorporating a CAG payload on future satellites, and the GPS control segment and user equipment contractors, IBM and Rockwell-Collins, are considering the effect of CAG on the GPS. The CAG concept and the preliminary design features described in this paper may be modified as new information is developed by the contractors and through discussion with potential users.
Published in:	Proceedings of the 49th Annual Meeting of The Institute of Navigation (1993) June 21 - 23, 1993 Royal Sonesta Hotel Cambridge, MA
Pages:	219 - 230
Cite this article:	Siegal, Barry, Munjal, Prem K., Sung, Robert, Ananda, Mohan, "Communication Satellite Augmented GPS," Proceedings of the 49th Annual Meeting of The Institute of Navigation (1993), Cambridge, MA, June 1993, pp. 219-230.
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