STABILITY OF GEODETIC GPS TIME LINKS AND THEIR COMPARISON TO TWO-WAY TIME TRANSFER

摘要

We quantify and analyze the time differences between simultaneous results for several pairs of TAI laboratories using the Two-Way satellite Time Transfer (TWTT) and different techniques using geodetic GPS methods. These include the combined clock products from the International GPS Service (IGS) and dual-frequency P3 common-view time transfers. Usable results are available for a few baselines over several months. The IGS and P3 results derive from the same GPS receivers, but P3 uses only the code measurements, while the IGS geodetic clocks use code plus phase and much more comprehensive modeling of the signal propagation. In addition, we compare these results to those obtained with C/A code GPS time receivers in classical common-view mode. All comparisons show levels of short-term noise and longer-term systematic effects well below 1 ns, with the exception of those involving the C/A code time receivers and a specific TWTT link. From the different comparisons and their interpretation, we infer the level of short-term noise and longer-term systematic effects for all techniques.