End-Of-Life Indicators for Nima's High-Performance Cesium Frequency Standards

C. Brock, B.W. Tolman, R.E. Taylor

Abstract:	The National Imagery and Mapping Agency (NIMA) operates a worldwide network of GPS monitoring stations that utilize high-performance cesium frequency standards and geodetic quality GPS receivers. The NIMA Monitor Station Network (MSN) operates continuously, and has been in operation for more than 7 years. The frequency standards are located in nonlaboratory environments and logistically challenging locations. The mean lifetime of the cesium-beam tube (CBT) is approximately 6 years; failure or end-of-life of the CBT is a significant cause in the reduction of data used to produce the NIMA GPS precise ephemeris. This paper considers methods of predicting CBT failure and end–of-life by examining a variety of data, collected over a 7-year period, by the NIMA MSN. Several operational parameters that are available from the frequency standard hardware, which are routinely collected by the NIMA GPS Monitor Station Control Center (MSNCC), are examined. The relative clock phase of the frequency standards in a zero-baseline configuration (in the stations that have redundant hardware) is also considered as a predictor, by using GPS carrier-phase time transfer techniques.
Published in:	Proceedings of the 34th Annual Precise Time and Time Interval Systems and Applications Meeting December 3 - 5, 2002 Hyatt Regency Reston Town Center Reston, Virginia
Pages:	117 - 126
Cite this article:	Brock, C., Tolman, B.W., Taylor, R.E., "End-Of-Life Indicators for Nima's High-Performance Cesium Frequency Standards," Proceedings of the 34th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, December 2002, pp. 117-126.
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