Time Activities at the BIPM

E. F. Arias and G. Panfilo

Abstract:	Almost 70 laboratories participate at present to the calculation of TAI and UTC at the BIPM. Their contributions involve about 350 atomic clocks linked by various techniques. Significant progress has been made in time transfer for clock comparison at the BIPM in 2008, either in the routine calculation of Circular T or in studies tending to enhance the quality of the reference time scales. Most time links (70%) are computed from multi-channel GPS receivers, either singlefrequency or dual-frequency; 15% of the links from TWSTFT observations in Europe, North America, and the Asia-Pacific region. The section treats, in total, TW observations from 20 laboratories, half of them not still included in the routine calculation, but under study aiming at their inclusion. Studies on the use of TW for supporting GPS equipment calibration were undertaken and used for a particular link. Following the recommendation of the Consultative Committee for Time and Frequency (CCTF) in 2006, a pilot experiment whose aim is to regularly compute some TAI links with the Precise Point Positioning (PPP) technique was proposed to time laboratories. More than 20 laboratories participate in this experiment, whose results are regularly published on the ftp server of the BIPM. GPS equipment calibration continued during the last year, reports have been published, and a Web page has been created to favor the dissemination among laboratories of results of calibrations, and organization of future campaigns. Studies to analyze the influence of some types of atomic standards on TAI have started with the aim of investigating a new possible procedure for the frequency prediction of the hydrogen maser.
Published in:	Proceedings of the 40th Annual Precise Time and Time Interval Systems and Applications Meeting December 1 - 4, 2008 Hyatt Regency Reston Town Center Reston, Virginia
Pages:	657 - 662
Cite this article:	Arias, E. F., Panfilo, G., "Time Activities at the BIPM," Proceedings of the 40th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, December 2008, pp. 657-662.
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