CHAMP Clock Characterization Revisited

Summary

The behaviour of the space-borne CHAMP GPS receiver clock over nearly three years is inspected by the results of the Rapid Science Orbit (RSO) determination and the on-board navigation solution (NAV). The analysis completes and enhances the results of the clock characterization study carried out earlier on a limited number of data. It is shown, that CHAMP on-board events like software uploads and hardware reboots frequently lead to large clock offsets, which are reduced on-board within a few hours. Comparisons of RSO and NAV solutions show, that the RSO clock offset estimates are additionally affected by bias and drift of the reference clocks chosen in the processing. The two independent solutions, RSO and NAV, indicate, that the CHAMP clock is free of a drift in the long term. In the short term, the clock parameters show a standard deviation of 0.4 µ/s and a small negative bias of 0.3 to 0.4 µ/s.