Effect of Broadcast ahd Precise Ephemerides on Estimates of the Frequency Stability of GPS NAVSTAR Clocks

Thomas B. McCaskill, Wilson G. Reid, James A. Buisson and Hugh E. Warren

Abstract:	Frequency stability analysis of on-orbit Navstar clocks is performed by the Naval Research Labora- toryt using both the broadcast and the precise post- processed ephemerides. The phase offset between the Navstar clock and the reference clock is computed from pseudorange measurements obtained by dual- frequency GPS receivers at the five GPS monitor sites and at the U.S. Naval Observatory precise-time site. The broadcast ephemerides are generated at the GPS Master Control Station by a Kalman filter using data collected from the five GPS monitor stations. The pre- cise post-processed ephemerides are generated by the Defense Mapping Agency (DMA) using data collected from the GPS monitor sites and from five additional DMA monitor sites. In this paper the frequency sta- bility is estimated for two Navstar cesium clocks-a Block I cesium clock (Navstar 9) and a Block II ce- sium clock (Navstar 23)-using both the broadcast and the precise ephemerides. A significant improve- ment in the estimate of the frequency stability of the Block II clocks has been achieved using the precise ephemeris.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	121 - 128
Cite this article:	McCaskill, Thomas B., Reid, Wilson G., Buisson, James A., Warren, Hugh E., "Effect of Broadcast ahd Precise Ephemerides on Estimates of the Frequency Stability of GPS NAVSTAR Clocks," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 121-128.
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