Performance Evaluation and Analysis of Galileo Satellite Clock in Orbit

Abstract

The Galileo system is currently the only satellite navigation system for large-scale, normalized assembly of high-precision, high-performance space-borne hydrogen atomic clocks. The analysis of the long-term performance of its satellite clocks contributes to the overall assessment of the system. Based on the precision clock offset products of the German Geoscience Research Center, the frequency accuracy and frequency drift rate of the satellite clock are calculated by the least squares fitting clock offset data. The frequency stability of the satellite clock is discussed by using the overlapping Hadamard variance. At the same time, the long-term variation characteristics of the residual sequence of the Galileo satellite clock offset model are analyzed and the accuracy statistics are obtained. Then the periodic term of the satellite clock is extracted according to the spectrum analysis method. Finally, the noise type of the satellite clock is identified by the Lag1 autocorrelation method. The indicators obtained by the above method comprehensively evaluate the performance of the Galileo satellite clock in orbit. The results show that the mean of frequency accuracy, frequency daily drift rate, frequency stability in ten thousand seconds and model fitting residual accuracy of the Galileo satellite clock are respectively $1.79\; \times \;10^{ - 11}$, $1.46\, \times \,10^{ - 14}$, $1.32\, \times \,10^{ - 14}$ and $0.102\;{\text{ns}}$; The Galileo satellite clock offset sequence has significant periodic characteristics, and the first three main periods are approximately 0.5, 1 and 0.33 times of its satellite orbital period; The Galileo satellite clock is mainly affected by WFM, FFM and RWFM at different smoothing times.