Design of a GNSS: Coverage, Accuracy and Integrity

V. Ashkenazi, T. Moore, C. J. Hill, W. Y. Ochieng, and Wu Chen

Abstract:	The concept of a civil owned Global Navigation Satellite System (GNSS) has evolved due to the concerns of the civilian navigation community over the current satellite positioning systems, GPS and GLONASS. Neither of these two systems provide continuous satellite availability and integrity, and both of them have been developed as military systems owned by single nations, with no absolute guarantee of continuity of service. In the case of GPS, the implementation of Selective Availability (SA) to degrade navigation accuracy means that full GPS navigation accuracy is inaccessible to the civilian community. Various options have been proposed, and some implemented, to address these concerns. These range from joint (US) military (DOD) and civilian (DOT) control of GPS, augmentation by using other satellite systems (eg. geostationary communications satellites), to the eventual deployment of a new GNSS wholly owned by the civilian community. It has also been suggested that the task of finding a successor to GPS should follow an evolutionary process, culminating in the deployment of the new GNSS. The approach is therefore a gradual one, starting with the current GPS constellation and enhancing its potential, in stages, through augmentation with existing satellites, such as communication satellites in Geostationary Orbits (GEO), GLONASS, and with planned satellite constellations in Low Earth Orbit (LEO) and Medium Earth Orbit (MEO). Suggestions have also been made, involving satellites in Highly Elliptical Orbits (HEO). The paper addresses the theoretical and practical aspects of candidate configurations and assesses satellite coverage (and hence navigational potential) and tbe provision of system integrity. The analysis includes an investigation into the design of satellite orbits advocated for use within a GNSS environment such as Geostationary Orbits (GEO), Low Earth Orbits (LEO), Medium Earth Orbits (MEO) and Highly Elliptical Orbits (HEO).
Published in:	Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995) September 12 - 15, 1995 Palm Springs, CA
Pages:	463 - 472
Cite this article:	Ashkenazi, V., Moore, T., Hill, C. J., Ochieng, W. Y., Chen, Wu, "Design of a GNSS: Coverage, Accuracy and Integrity," Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995), Palm Springs, CA, September 1995, pp. 463-472.
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