RAIM Detection and Isolation Integrity Availability With and Without CAG

Mohan Ananda, Jurn Leung, Prem Munjal, and Barry Siegel

Abstract:	The Federal Aviation Administration (FAA) is cur- rently considering the use of GPS as the primary, sole means system to achieve the required navigation performance @NP) capability without any external backup. In addition to the development of a Wide Area Augmented System (WAAS), receiver autonomous integrity monitoring (RAN) is an essential component in system integrity and flight safety enhancement. The purpose of this paper is to evaluate RAIM detection and lay the groundwork for isola- tion availability studies under the current GPS constellation with and without CAG satellites. The study provides RAIM detection availability results for DOD user receivers aug- mented by BAR0 aiding for the non-precision approach flight phase. All-in-view tracking is assumed. The impact of constellation depletion on RAIM availability is addressed as well as the effect of GPS constellation augmentation by geosynchronous satellites. The paper presents results of RAIM outage, which is defined as the time period when any of the integrity availability requirements with respect to time to alarm, navigation accuracy, and conditions for fault detec- tion and isolation are not met at a given location. In order to provide an overview of system integrity and availability the paper also presents a simplified analytical expression that relates the GPS integrity availability to that of RAIM and geostationary integrity channel (GIC) and the likelihood of signal-in-space failures. This analysis indicates that if signal-in-space fail- ure rates are low, the current GPS constellation can meet military user threshold RAIM integrity requirements (0.999) at most locations. With geosynchronous augmen- tation (CAG), 0.99999 integrity availability can be pro- vided at all locations.
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:	619 - 630
Cite this article:	Ananda, Mohan, Leung, Jurn, Munjal, Prem, Siegel, Barry, "RAIM Detection and Isolation Integrity Availability With and Without CAG," 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. 619-630.
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