DUAL FREQUENCY P-CODE TIME TRANSFER EXPERIMENT

J.R. Clynch and B.W. Tolman, M.A. Weiss, D.W. Allan, D. Davis

Abstract:	The Clock Evaluation and Time Keeping Experiment was the cooperative effort of Applied Research Laboratories, the National Bureau of Standards, and the United States Naval Observatory. It was designed to collect a dense Global Positioning System (GPS) data set for evaluating methods of monitoring a ground-based atomic clock with on-site data alone, and of investigating improved methods of time setting and time transfer using GPS data. The experiment collected two-frequency, P-code, pseudorange and Doppler data for five weeks at three sites; Austin, Texas; Boulder, Colorado; and Washington, D.C. All sites used two-frequency receivers on cesium oscillators. A time history of the cesium oscillators against hydrogen masers also was recorded at two of the sites. Comparison of the range residuals for the broadcast and the precise ephemerides shows a difference of up to 50 ns, with a pattern that was generally repeated each day during the experiment. The pattern is likely due to the broadcast ephemeris. Clock recovery using such data should be possible at the 30 ns level, but recovery of frequency information will require several days' data. The behavior of the cesium oscillators was well tracked by the range residuals over the five weeks of the experiment. Residuals of Doppler data were strongly correlated across stations. This implies that time transfer with accuracy approaching 2 ns looks promising over the time period of one satellite pass. With a full GPS constellation, continuous use of phase data could significantly improve time transfer via GPS.
Published in:	Proceedings of the 19th Annual Precise Time and Time Interval Systems and Applications Meeting December 1 - 3, 1989 Sheraton Hotel Redondo Beach, California
Pages:	25 - 32
Cite this article:	Clynch, J.R., Tolman, B.W., Weiss, M.A., Allan, D.W., Davis, D., "DUAL FREQUENCY P-CODE TIME TRANSFER EXPERIMENT," Proceedings of the 19th Annual Precise Time and Time Interval Systems and Applications Meeting, Redondo Beach, California, December 1987, pp. 25-32.
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