Sagnac Effect and Diurnal Correction on Two-Way Satellite Time Transfer

Precision of two-way satellite time and frequency transfer (TWSTFT) highly depends on the residual nonreciprocity delays; one of them is caused by the Sagnac effect. In this paper, we employ the satellite ephemeris data to compute the precise Sagnac effect and discuss the possible additive effect related to the Sagnac effect. We also describe a method to calculate the diurnal correction based on the time derivative of the Sagnac effect. Through the analysis of the link between the National Institute of Information and Communications Technology in Japan and the Telecommunication Laboratories in Taiwan, we demonstrate that the correction was useful to improve the TWSTFT data. The time deviation at an 8-h averaging time is reduced from 346 to 156 ps after the correction.