Impact of Discrepancies between Received Delay and Carrier at Remote TWSTFT Stations Caused by Satellite Motion

In this paper, we calculate the difference of carrier frequencies at remote stations with considering the satellite motion and evaluate its impact on the TWSTFT data. The results show that the diurnals in transatlantic TWSTFT links have a clear correlation with the difference of fractional carrier Doppler frequencies between two stations. We also correct the diurnals with a linear correlation coefficient of 1 ns/10-9 between two-way time transfer data and fractional carrier Doppler difference. The results show that time stabilities (TDEVs) at the 12h averaging time are reduced from 234 ps to 106 ps for the NIST-PTB link as the corrections are applied. The possible explanation is that the code and carrier tracking loops share the same correlators in receivers. Whenever there are discrepancies of change rates between delay and carrier in a receiver, residual error of a tracking loop may have an impact to the other.