Accuracy of GPS Time Transfer Verified by Closure Around the World

W. Lewandowski, G. Petit, C. Thomas

Abstract:	The precision of time transfer over intercontinental distances by the CPS common-view method, using measurements of ionospheric delays, precise ephemerides provided by the DMA and a consistent set of antenna coordinates, reaches 3-4 ns for a sin& 13-min measurement, and decreases to 2 ns when averaging several measurements over a period of one day. It is thought that even this level of precision can be bettered by improving the ionospheric measurements, the ephemerides of the satellites and the antenna coordinates. In the same conditions, an estimation of the accuracy is attained by using three intercontinental links encircling the Earth to establish a closure condition: The three independent time links should add to zero. We have computed such a closure condition over a period of thirteen months using data recorded at the Paris Observatory in Paris (France), at the Communications Research Laboratory in Tokyo (Japan) and at the National Institute for Standards and Technology in Boulder, Colorado (USA). The closure condition is verified to within a few nanoseconds but a bias, varying with time, can be detected.
Published in:	Proceedings of the 23th Annual Precise Time and Time Interval Systems and Applications Meeting December 3 - 5, 1991 Pasadena, California
Pages:	331 - 339
Cite this article:	Lewandowski, W., Petit, G., Thomas, C., "Accuracy of GPS Time Transfer Verified by Closure Around the World," Proceedings of the 23th Annual Precise Time and Time Interval Systems and Applications Meeting, Pasadena, California, December 1991, pp. 331-339.
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