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A Long-Term Comparison of GPS Carrier-Phase Frequency Transfer and Two-Way Satellite Time/Frequency Transfer



C Hackman, Judah Levine, Thomas E. Parker


GPS carrier-phase frequency transfer (GPSCPFT) and two-way satellite time and frequency transfer (TWSTFT) were performed along three trans-Atlantic links over the six-month period 29 January ¿ 31 July 2006. The GPSCPFT and TWSTFT results were subtracted in order to estimate the combined uncertainty of the methods. The frequency values obtained from GPSCPFT and TWSTFT agreed at 1.8 to 3.8󈵒-16 RMS for averaging times of 30 d, with no single value of yGPSCPFT ¿ yTWSTFT exceeding 5.5󈵒-16. These RMS frequency-accuracy values were equal to or less than the frequency-stability values ςy(GPSCPFT) ¿ y(TWSTFT) (τ) (or TheoBR (τ)) computed for the corresponding averaging times; in general, no frequency bias between GPSCPFT and TWSTFT was observed. The transfer noise of the links varied with time of year, which was especially noticeable in the yGPSCPFT ¿ yTWSTFT values obtained for 10-15 d averaging times: yGPSCPFT ¿ yTWSTFT (10 d) sometimes became as large as 2󈵒-15. It is not yet clear what caused these variations. RMS (yGPSCPFT ¿ yTWSTFT, 10 d) ranged from 0.7 to 1.1󈵒-15, with these RMS values approximately equal to ςy(GPSCPFT) ¿ y(TWSTFT) (τ {equals} 10 d, 21 h). Day-boundary discontinuities were not removed or otherwise circumvented in this experiment; we hope to reduce the uncertainty at shorter averaging times (e.g. 10 d) through better management of these discontinuities along with improved understanding of the seasonal components.
Proceedings Title
Proc. 2006 PTTI Mtg.


carrier phase frequency transfer, carrier phase time transfer, GPS, GPSCPFT, GPSCPTT, satellite time transfer, satellite frequency transfer, two way, TWSTFT


Hackman, C. , Levine, J. and Parker, T. (2006), A Long-Term Comparison of GPS Carrier-Phase Frequency Transfer and Two-Way Satellite Time/Frequency Transfer, Proc. 2006 PTTI Mtg., [online], (Accessed April 15, 2024)
Created December 5, 2006, Updated February 17, 2017