论文部分内容阅读
Broadcast ephemeris accuracy is an important index of GNSS navigation system performance evaluation. As a component of broadcast ephemeris, the accuracy of predicted clock offset will directly affect the accuracy of navigation, positioning and timing. In order to access the accuracy of Galileo broadcast clocks, the content and characteristics of Galileo broadcast ephemeris are introduced in this paper first. Then, the principle and method of accuracy evaluation of broadcast ephemeris are explained. On this basis, the broadcast ephemeris data in the last two years since Galileo provided the initial service were used to analyze the accuracy of broadcast clock offset. As a comparison, the GBM precision clock offset products provided by GeoForschungsZentrum Potsdam (GFZ) analysis center was taken as the truth value. The results show that: (1) The STD of broadcast clock offset of 15 Galileo satellites providing normal services is about 1ns. The RMS of the broadcast clock offset is about 1ns, except that of E24 which is 5.7ns. (2) After the Galileo satellites provided service, the STD and the RMS of broadcast clock offset changes are within 1ns and 1~1.4ns, respectively, which partly reflects the stability of Galileo space-borne clock. The results would provide some reference for timing applications of Galileo satellite navigation system.