SATELLITE CRITICALITY CONCEPTS FOR UNAVAILABILITY AND UNRELIABILITY OF GNSS SATELLITE NAVIGATION

Curtis Shively

Peer Reviewed

Abstract: This paper derives expressions and approximations for unavailability and unreliability of navigation service using Global Navigation Satellite System (GNSS) satellites. Both unavailability and unreliability are shown to be characterized by a concept known as critical satellites-a critical satellite is used in every satellite combination with good satellite-user geometry. Numerical results are given, showing the levels of unavailability and unreliability associated with the satellite criticality characteristic. In the case of unreliability, these numerical results are compared with existing reliability requirements for precision approach using the Instrument Landing System (ILS). Insights provided by the critical satellite concept are illustrated with an example of instantaneous unavailability for a Category I (CAT I) precision approach application. This example relates temporal peaks of unavailability to satellite criticality and quantifies the degradation of geometry due to critical satellite failures.
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 40, Number 4
Pages: 429 - 450
Cite this article: Shively, Curtis, "SATELLITE CRITICALITY CONCEPTS FOR UNAVAILABILITY AND UNRELIABILITY OF GNSS SATELLITE NAVIGATION", NAVIGATION, Journal of The Institute of Navigation, Vol. 40, No. 4, Winter 1993-1994, pp. 429-450.
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