Where Should Changes be Made? Correcting the Effects of Satellite Anomalies on GPS Receivers

John W. Lavrakas, Daniel Knezha, Shane Connary

Abstract:	At the ION NTM-99 meeting, Mr. Lavrakas and Mr. Knezha reported on the different responses GPS receivers have to certain categories of satellite anomalies. Their report showed that receivers experience large code and phase jumps, extended loss of lock, and reassignment of satellites in solution sets all of which can adversely affect the user. This paper builds on both the research conducted by Mr. Lavrakas and Mr. Knezha, along with research performed by 1Lt. Brian Barker and 1Lt Stacy Huser, United States Air Force, focusing on a space segment perspective of the anomalies observed by Overlook Systems Technologies. This paper focuses on the first ever fusion of analysis across the boundaries of the space, ground and user segment. Specific anomalies were detected, recorded, analyzed and reported upon from the perspective of the end user using multiple receivers, and from the perspective of the satellite system operator. Data was gathered simultaneously from the satellite broadcasting the navigation message, the control segment monitoring the internal performance of the spacecraft’s processor, and various receivers using the navigation message for ranging and positioning. This information allowed us to determine if Interface Control Document (ICD) specifications truly protect the user, and we provide specific recommendations for a way ahead in addressing these types of anomalies. This information will be of great interest to GPS receiver manufacturers and users seeking to minimize the operational effects of these anomalies.
Published in:	Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999) June 27 - 30, 1999 Royal Sonesta Hotel Cambridge, MA
Pages:	603 - 607
Cite this article:	Lavrakas, John W., Knezha, Daniel, Connary, Shane, "Where Should Changes be Made? Correcting the Effects of Satellite Anomalies on GPS Receivers," Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999), Cambridge, MA, June 1999, pp. 603-607.
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