Combination of TWSTFT and GPS data for time transfer

摘要

This paper presents a time transfer method based on a least-square analysis of the GPS code and carrier-phase measurements in common view (CV), constrained by TWSTFT (TW hereafter) data. Combining GPS and TWSTFT considerably increases the robustness of the remote clock comparisons thanks to the complete independence between these two techniques. An additional goal of the combination (named CV + TW) is to provide a time transfer solution, which benefits from the high short-term stability and high resolution of the GPS data and from the high accuracy of the TW data. The final solution is then calibrated by the TW data rather than by the GPS pseudoranges. As a consequence, the large day-boundary discontinuities that can exist in GPS time transfer solutions disappear in the combined solution, and are replaced by smaller discontinuities the magnitude of which depends on the noise level of the TW link. For a very noisy link, we found jumps up to 1 ns, while for the very quiet link NIST-OP, they are all lower than 200 ps.