NAGUs: An Analysis of GLONASS Availability Statistics

David Holmes and Mike Trethewey

Abstract:	It is possible to derive availability statistics for each GLONASS satellite using NAGUs (Notice Advisory to GLONASS Users). Since 19 January 1996 when the GLONASS system was declared fully operational there have been few occasions when the full complement of 24 satellites was operating. However, since this date 7 satellites have been declared non-operational and have been withdrawn from the constellation. These satellites experienced long outages before they were withdrawn. The problems experienced by GLONASS satellites are highly correlated to their lifetime. The current design lifetime of a satellite is 3 years, and with a few exceptions satellites younger than this have performed well. Although average lifetimes are improving older satellites tend to suffer extended outages. A comparison of NAGU reports with data collected by Signal Computing in the UK suggests that many outages are unplanned, and may be due to a malfunction on the satellite. Although there have been a number of additional outages that have not been reported in NAGUs, these represent only a small fraction of the total.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	1521 - 1525
Cite this article:	Holmes, David, Trethewey, Mike, "NAGUs: An Analysis of GLONASS Availability Statistics," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 1521-1525.
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