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A TWSTFT calibration guideline and the use of a GPS calibrator for UTC TWSTFT link calibration



Zhiheng Jiang, Demetrios Matsakis, Victor S. Zhang, Hector Esteban, Dirk Piester, Shinn-Yan Lin


Two-Way Satellite Time and Frequency Transfer (TWSTFT) links were first introduced to the Coordinated Universal Time (UTC) generation in 1999 [1,19]. These TWSTFT links were calibrated by alignment with the corresponding GPS time links, of which the nominal uncertainty was 5 ns. In the past decade, the primary calibration technique for TWSTFT link calibrations was based on a TWSTFT mobile ground station (MB) with uncertainty at the level of 1 ns [2,3,15,21,22]. The use of MB in TWSTFT link calibration is limited by the availability of the MB and high cost. Alternated techniques have been proposed and validated in the recent years. In this paper, we first outline the new TWSTFT Calibration Guidelines for UTC Time Links (v3.0) [7], which was approved at the 23rd meeting of the Consultative Committee for Time and Frequency (CCTF) Working Group on TWSTFT. It authorizes several techniques, including the GPS link calibration [10,27] and the Tringale Closure Calibration (TCC) [18,25]. We then discuss the attainable uncertainty of the GPS link calibration [14,16,17]. Finally we show in the Annex an example report of using a GPS calibrator for a typical UTC time link calibration based on the US Naval Observatory (USNO) and PTB TWSTFT link calibration [23,26]. Here we describe the characteristics of BIPM's Measurement of Total Delay (METODE) Global Navigation Satellite System (GNSS) calibrator, its setup at a UTC laboratory, Lab(k), measurements, and results. In this calibration, the GPS result differs from that of the TWSTFT MB by 0.9 ns with an uncertainty of 1.5 ns.
Proceedings Title
The Precise Time and Time Interval Systems and Applications (PTTI)2016 Proceedings
Conference Dates
January 26-28, 2016
Conference Location
Monterey, CA, US


Calibration Guidelines, Uncertainty, GPS time link calibration, TCC calibration, METODE


Jiang, Z. , Matsakis, D. , Zhang, V. , Esteban, H. , Piester, D. and Lin, S. (2016), A TWSTFT calibration guideline and the use of a GPS calibrator for UTC TWSTFT link calibration, The Precise Time and Time Interval Systems and Applications (PTTI)2016 Proceedings, Monterey, CA, US (Accessed May 29, 2023)
Created January 24, 2016, Updated October 12, 2021