“Common view” clock synchronization of remote atomic clocks using GPS and PRARE onboard ERS-2

The paper presents a validation test for two-way clock comparison with the help of the PRARE instrument onboard ERS-2 and with two of the PRARE system stations, which are provided with atomic clocks. A “Common View” ground-clock synchronization scenario has been performed, using the PRARE instrument and GPS time receivers connected to an atomic clock at each ground station site. By computing and comparing the results respectively the accuracy for the PRARE instrument has been estimated. The achievable synchronization accuracy for the PRARE equipment in this “Common View” mode is around 1 ns, due to the sub-optimum design of the existing PRARE system for time purposes. The experiment turns out that the PRARE system combined with a highly stable frequency source onboard a suitable satellite is qualified to be a basic element for a future GNSS II