Performance Analysis of the On-board Atomic Clocks for BeiDou-3 Satellites

15 BeiDou-3 MEO satellite clocks have been chosen to be studied by using the MGEX (Multi-GNSS Experiment) final clock offsets product provided by the IGS (International GNSS Service) MGEX Analysis Centre - WUHAN University. These clock offsets cover from January 1st to July 1st, 2019, or day-of-year (DOY) 001 to 182. After pre-processed these clock offsets are used to calculate the overlapping Hadamard deviation at the 1000 s and 10000 s time interval, and the method of quadratic polynomial fitting is performed to obtain the daily frequency drift. The characterization of every On-board atomic clock for the 15 BeiDou-3 satellites is analyzed. It shows that the frequency stability of satellite clocks is on the order of E-14. The day frequency drifts of C19–C24, C32 and C33 are generally within the order of E-13. Those of C25–C30 and C34 are generally within the order of E-14. Comparing the on-orbit performance of C19–C24 satellite clocks with their ground test records, the results show that these twos are equivalent for thousand-second frequency stability, and as for ten-thousand-second frequency stability on-orbit performance of these satellite clocks is slightly worse than their ground test records for which an analysis is given. Except for the satellite C24, the daily frequency drifts of the other 14 satellite clocks are better than the ground test records or at least equivalent.