Atomic clock performance and combined clock error prediction for the new generation of BeiDou navigation satellites

Atomic clocks are the core equipment aboard navigation satellites, and their performances and predictions directly determine PNT accuracy. In this paper, the on-orbit performances and prediction accuracies of atomic clocks used in new generation navigation satellites are evaluated using two-way time synchronization data. First, using clock error data preprocessed based on combined MAD gross error detection, the method used to evaluate satellite clock performance is studied. The results illustrate that gross error can be eliminated effectively and that the performances of the new generation of satellites are improved in comparison with those of regional satellites. The frequency accuracy has been enhanced from 6.91 x 10(-12) to 3.29 x 10(-12), and daily stability has been enhanced from 4.036 x 10(-14) to 2.339 x 10(-14). Second, a weighted combined clock error prediction model was designed that synthesizes polynomial and gray models using the classical weighted method. The results using the combined models show that the prediction accuracies of the new generation satellites are improved by a factor of two when compared with those for regional satellites, and the mean prediction was enhanced was from 0.77 ns to 0.38 ns. Moreover, from the research findings, it was found that prediction accuracy is significantly correlated with daily stability and frequency accuracy and has a micro-correlation with daily drift rate. Finally, in order to study the prediction accuracies of the new generation of satellites, we studied ISL and concluded that it has greatly increased the measured arc of the MEO satellites and can improve re-entry prediction accuracies from 3-4 ns to 1 ns. (C) 2018 COSPAR. Published by Elsevier Ltd. All rights reserved.