The state of the signal in space (SIS) broadcasted by the broadcast ephemeris will affect the reliability and safety of the user navigation and positioning. Understanding the SIS anomaly of a satellite is conducive to fault allocation in advanced receiver autonomous integrity monitoring. In this study, precise ephemeris was used to calculate the SIS error of all healthy Galileo satellites from 2017 to 2018, the detection thresholds were obtained through statistics of SIS error, and the satellite SIS anomalies for two years were detected. Results show that the SIS anomalies of Galileo satellites are primarily caused by satellite clock error, the scale of which can sometimes reach tens or even hundreds of metres. Except for E24 satellite, the annual accumulation of anomalies for Galileo satellites was <∼7 h, and the average annual accumulation of anomalies is ∼2.5 h. The accumulation of anomalies for E24 in 2017 was ∼50 h∼50 h, but this decreased to 4.5 h in 2018, indicating that its stability improved. Overall, the SIS stability in 2018 was improved compared with 2017. In addition, as the serious missing of broadcast ephemeris of Galileo satellites, it is not conducive to the continuity and reliability of the user's navigation and positioning.

中文翻译：

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2017年至2018年空间异常中伽利略信号的检测与分析

广播星历表广播的太空信号状态（SIS）将影响用户导航和定位的可靠性和安全性。了解卫星的SIS异常有助于进行高级接收机自主完整性监控中的故障分配。在这项研究中，使用精确星历来计算2017年至2018年所有健康伽利略卫星的SIS误差，通过SIS误差的统计获得检测阈值，并检测了两年的卫星SIS异常。结果表明，伽利略卫星的SIS异常主要是由卫星时钟误差引起的，其误差有时可能达到数十米甚至数百米。除E24卫星外，伽利略卫星的年累积异常量<〜7小时，平均年累积异常量约为2.5小时。E24在2017年的异常累积为〜50h〜50h，但在2018年降至4.5h，表明其稳定性有所提高。总体而言，与2017年相比，2018年的SIS稳定性得到了改善。此外，由于伽利略卫星广播星历的严重缺失，不利于用户导航和定位的连续性和可靠性。