Final Report of the BIPM Pilot Study on UTC Time Link Calibration

Z. Jiang

Abstract:	UTC is represented by the differences of [UTC-UTC(k)], which is strongly correlated to the time link between the Lab(k) and the pivot lab of the UTC network. As shown in [4], on average 98% of the uncertainty in UTC-UTC(k) comes from the related time link. The calibration of UTC time transfer is in principle the time link calibration. Obviously, a direct link calibration will result in a maximum reduction in the uncertainty. In 2011 the BIPM launched a pilot study on the accurate calibration of UTC time links [2,20], which represented a departure from the classic equipment-based calibration. The goal is to improve and unify the UTC time link calibration uncertainties to less than 2 ns. This is attainable using the BIPM ‘all-in-one’ METODE (MEasurement of TOtal DElay [3]) scheme and a dedicated travelling calibrator (StdB). The METODE calibration result is the total delay correction (CM) that can be easily converted to the classic equipment internal delays INTDLY(P1/P2) [1,23] for GPS geodetic receivers. During 2013 and 2015 [20], eleven leading laboratories participated in the project. The related UTC time links have been calibrated with an uncertainty of 1~2 ns [3,5]. This uncertainty evaluation is supported by other independent studies [10-16]. Based on the result of the pilot study, the recently approved ‘TW guideline for UTC Time Links’ authorizes the GPS link calibration as an alternative technique for the TWSTFT UTC time link calibration [7,8]. Operational guidelines have been prepared [19] and used to guide the METODE calibration tours and data processing [20]. This paper is the final report of the pilot study. We review the background and the state-of-the-art of the link calibrations, the principle of METODE, data processing, the calibration results, evaluation of the uncertainty and cross comparisons to other independent and more accurate calibration results, such as those of the TWSTFT mobile station (MS) and optical fibre link.
Published in:	Proceedings of the 47th Annual Precise Time and Time Interval Systems and Applications Meeting January 25 - 28, 2016 Hyatt Regency Monterey Monterey, California
Pages:	20 - 26
Cite this article:	Jiang, Z., "Final Report of the BIPM Pilot Study on UTC Time Link Calibration," Proceedings of the 47th Annual Precise Time and Time Interval Systems and Applications Meeting, Monterey, California, January 2016, pp. 20-26. https://doi.org/10.33012/2016.13142
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