USE OF THE GPS TIME TRANSFER AT THE BUREAU INTERNATIONAL DES POIDS ET MESURES

B. Gulnot, W. Lewandowski

Abstract:	The majority of the laboratories contributing to the establishment of the International Atomic Time TAI are now equipped with GPS time receivers. The BIPM coordinates the international time comparisons by GPS and evaluates most of the time links that are needed for the International Atomic Time TAI. The BIPM also participates to the calibration of instrumental delays by transportation of a receiver. In the practice of GPS time comparisons, it appears that one is often rather far from reaching the potential accuracy. We have made a study of some of the limiting factors. Among them are the errors of the antenna coordinates: we show that they can be improved from the time measurements so that an accuracy of about 2 ns can be reached over short distances. An other source of difficulties is the lack of stability of some local time scales, which restricts the possibility of improving the precision by filtering; this difficulty appears mainly with the clocks which are too sharply steered. The tracking schedules in use aim at providing links between the greatest possible number of laboratories. One of our conclusion, which should be discussed with the cooperating laboratories, is that one should organize a worldwide network of links which should be optimized not for the number of links, but for the accuracy of the necessary links.
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:	3 - 11
Cite this article:	Gulnot, B., Lewandowski, W., "USE OF THE GPS TIME TRANSFER AT THE BUREAU INTERNATIONAL DES POIDS ET MESURES," Proceedings of the 19th Annual Precise Time and Time Interval Systems and Applications Meeting, Redondo Beach, California, December 1987, pp. 3-11.
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