Performance of GPS Monitor Station Time References and On-Orbit Navstar Clocks

Thomas B. McCaskill, Wilson G. Reid, Orville J. Oaks, Ronald L. Beard, James A. Buisson, Hugh E. Warren

Abstract:	Analyses by the U.S. Naval Research Laboratory (NRL) of the p er ormance f of clocks in the Global Positioning System (GPS) will be presented. The analyses are performed for all Navstar space vehicle clocks that have been operated on-orbit and for the time reference at each of the monitor stations of the GPS Control Segment. The behavior of the Navstar clocks currently in use will be described. The number) type, and length of operation of the on-orbzt clocks will be detailed and their positions in the constellation identified. A significant portion of the analysis will be devoted to the frequency drifi (aging) characteristacs of Navstar rubidium clocks because of an expected zncrease in the use of these clocks in the GPS constellataon. Analysis is performed using a multi-year database which includes pseudorange data collected from the tzrne of initial activation of each clock. The pseudorange data is collected from GPS Control Segment and Defense Mappzng Agency (DMA) receivers. These receivers gather the worldwide trackzng data necessary for system operation. Consequently, the data is corrected for Selective Availability and Anti-Spoofing. On-orbit clock performance is computed using the post-processed precise ephemerides supplied by DMA and observations collected at the DMA sate located at the U.S. hlaval Observatory (USNO,). All observations are referenced to the DOD Master Clock.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	241 - 249
Cite this article:	McCaskill, Thomas B., Reid, Wilson G., Oaks, Orville J., Beard, Ronald L., Buisson, James A., Warren, Hugh E., "Performance of GPS Monitor Station Time References and On-Orbit Navstar Clocks," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 241-249.
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