A Summary of the GPS Constellation Clock Performance

Jay Oaks, James A. Buisson, and Marie M. Largay

Abstract:	The Naval Research Laboratory (NRL) conducts comprehensive analyses of the Global Positioning System (GPS) atomic frequency standards under the sponsorship of the 2nd Space Operations Squadron (2SOPS) at the Master Control Station (MCS) in Colorado Springs, Colorado. The analysis is based on clock estimates that NRL computes from GPS monitor station carrier-derived pseudo-range measurements and National Geospatial-Intelligence Agency (NGA) computed precise post-fit orbit ephemerides. The purpose of the analyses is to determine the performance of the timing signals originating from the atomic frequency standards on board the space vehicles. Metrics used in the analyses include frequency, drift, stability profiles, and stability histories based on the Allan and Hadamard variances. The relative performance of the space vehicle clocks is ranked and presented according to the clock types flown in GPS. An overview of the GPS constellation with respect to the lifetimes of space vehicles and space vehicle clocks, both active and deactivated, is also presented.
Published in:	Proceedings of the 39th Annual Precise Time and Time Interval Meeting November 27 - 29, 2007 Hyatt Regency Long Beach Long Beach, California
Pages:	119 - 130
Cite this article:	Oaks, Jay, Buisson, James A., Largay, Marie M., "A Summary of the GPS Constellation Clock Performance," Proceedings of the 39th Annual Precise Time and Time Interval Meeting, Long Beach, California, November 2007, pp. 119-130.
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