北斗导航系统自2018年12月27日提供全球服务以来, 其服务性能受到了极大关注. 以上海天文台iGMAS (International GNSS Monitoring & Assessment System)分析中心发布的精密轨道、钟差产品作 为基准, 评估了2019年年积日3--12d的北斗二号、北斗三号以及GPS广播星历的轨道、钟差和空间信号用户测距误差(Signal in Space User Ranging Error, SISURE, 简称为URE), 并且对北斗卫星导航 系统结果进行了详细的分析. 结果表明: 在评估时间段内, 北斗三号广播星历轨道精度、URE均明显优于北斗二号, 且部分结果优于GPS. 北斗三号广播星历轨道 径向精度最高, 优于0.2m. 北斗三号全部卫星URE均值优于0.4m, URE RMS (root mean square)优于0.5m. 北斗二号每颗卫星URE均值、95%URE (置信度为95%的URE)、URE RMS小于2m, 北斗三号每 颗卫星URE均值、95%URE、URE RMS小于1m, 均达到了系统公开承诺的服务性能标准.
Since the Beidou navigation system provided a global service on 2018 December 27, its service performance has received great attention. Based on the precision products released by the iGMAS (International GNSS Monitoring & Assessment System) Analysis Center of Shanghai Astronomical Observatory, we evaluate the orbits, clock differences, and signal in space user ranging error (SISURE (URE)) of the Beidou-2, Beidou-3, and GPS during the day of year 3--12 of 2019, and analyze the results of the Beidou navigation system in detail. It is showed that the results of Beidou-3, including broadcast ephemeris orbit accuracy and URE, had an obvious superiority over Beidou-2 during the evaluated period. And a part of them were better than GPS. Meanwhile, Beidou-3 has the best broadcast ephemeris orbit accuracy in radial direction, less than 0.2m. Its average URE was less than 0.4m, and URE RMS was less than 0.5m. The parameters, including average URE, 95$%$URE, and URE RMS, were less than 2m in Beidou-2 and 1 m in Beidou-3, respectively, and all meet the service performance standards that the system publicly promises.