Developments in the Definition of Inmarsat's International Geostationary Overlay for GPS and GLONASS

G. V. Kinal, J. P. Singh

Abstract:	The concept of employing simple, non-autonomous satellite repeaters on geostationary hosts for civil radionavigation has been recommended by a number of authors. INMARSAT is developing further this concept, in cooperation with other organizations such as ESA, as a means of providing wide scale broadcast of GPS and GLONASS integrity warning; augmenting coverage and reliability to civil users worldwide; and, providing the core for future radio-determination services independent of GPS and GLONASS, should such a capability become required in the future. The present paper reviews the history of the geostationary repeater concept, especially for integrity broadcast and for augmentation. It is indicated how a worldwide geostationary overlay is likely to be more economical than launching additional autonomous navigation satellites. Also presented are recently developed technical considerations for such a concept, including design parameters for the navigation package; signal and data format considerations for augmentation and integrity; and ground network concepts for generating and timing the uplink signals. Early results of a test program being conducted with transmission of GPS-like signals via existing INMARSAT satellites are reported. The paper concludes with a description of possible further applications of the geostationary overlay. The overall conclusion is that the proposed overlay can provide a useful and cost effective enhancement for civil user communities worldwide, and affords governmental authorities an opportunity to add value and exercise a degree of independent oversight to the established GPS and GLONASS systems without the massive investments for extension of terrestrial navaids or the launching of dedicated navigation satellites.
Published in:	Proceedings of the 2nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1989) September 27 - 29, 1989 The Broadmoor Hotel Colorado Spring, CO
Pages:	393 - 401
Cite this article:	Kinal, G. V., Singh, J. P., "Developments in the Definition of Inmarsat's International Geostationary Overlay for GPS and GLONASS," Proceedings of the 2nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1989), Colorado Spring, CO, September 1989, pp. 393-401.
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