Evolution of the International Atomic Time TAI Computation

Michel Granveaud

Abstract:	The International Atomic Time TAI is a worldwide time reference. Its computation has changed during the last 10 years. Further changes would essentially depend on the improvement of the atomic clocks. The International Atomic Time TAI as computed by the Bureau International de l'Heure (BIH) is a worldwide time reference officially adopted in 1971 1]. It has been made available for the scientific community for 24 years. The time signals transmit Universal Time Coordinated UTC which is closely related to TAI. The TAI computation has involved atomic clocks, comparisons between the clocks and mathematical algorithms. It is intended to outline the main recent changes concerning the above three points and to have a look to some future possibilities of computing TAI. Atomic clocks The computation of TAI has been performed from the data of cesium clocks*. Some significant modifications, quantitative as well as qualitative, must be noted in the devices involved in it over the last decade as shown by the Figure 1. In 1962, about 45 commercial cesium clocks entered this computation, all of them being manufactured by the Hewlett-Packard company-models 5060A and 5061A-. The Hewlett-Packard option 4 clocks were introduced into the TAI clocks ensemble at the end of 1972.
Published in:	Proceedings of the 11th Annual Precise Time and Time Interval Systems and Applications Meeting November 27 - 29, 1979 Goddard Space Flight Center Greenbelt, Maryland
Pages:	185 - 195
Cite this article:	Granveaud, Michel, "Evolution of the International Atomic Time TAI Computation," Proceedings of the 11th Annual Precise Time and Time Interval Systems and Applications Meeting, Greenbelt, Maryland, November 1979, pp. 185-195.
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