GPS IIR Rubidium Clocks: In-Orbit Performance Aspects

Marvin Epstein, Gerald Freed, John Rajan

Abstract:	The GPS Block IIR rubidium clocks have proved to be the best performers in the current GPS constellation, starting with the first IIR operational clock (launched on July 23, 1997). This discussion covers a number of topics, including the frequency accuracy, the frequency variation, and the projected lifetimes of these clocks. The performance of these clocks in orbit and their life expectancy are compared with that experienced with previous GPS clocks. The superior performance and lifetimes of the GPS IIR Rb clocks are highlighted. Because these clocks are so well behaved, it has been possible to detect various features and phenomena that were not previously detectable. The full drift of the IIR clocks is not observed by the user because of onboard cancellation by the Time Keeping System. The diagnostic and re-programmability capability of the GPS IIR Satellites allows these discrepancies to be addressed. The long-lived features of the clocks indicate that they will outlive the GPS satellite mission duration.
Published in:	Proceedings of the 35th Annual Precise Time and Time Interval Systems and Applications Meeting December 2 - 4, 2003 Hilton Resort on Mission Bay San Diego, California
Pages:	117 - 134
Cite this article:	Epstein, Marvin, Freed, Gerald, Rajan, John, "GPS IIR Rubidium Clocks: In-Orbit Performance Aspects," Proceedings of the 35th Annual Precise Time and Time Interval Systems and Applications Meeting, San Diego, California, December 2003, pp. 117-134.
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