基于预报钟差的轨道快速恢复

我国北斗卫星导航系统由GEO/IGSO/MEO混合星座构成,基本每7~10 d就会有一颗GEO卫星或IGSO卫星进行轨控操作。从卫星轨控开始,卫星存在5~6 h的不健康时期。造成机动卫星长期不健康的关键因素之一在于卫星和测站钟差数据的积累周期较长。本文提出了一种基于预报钟差的轨道快速恢复算法,通过结合星钟和站钟预报压缩机动卫星定轨观测数据积累的时间,从而缩短卫星恢复所需时间。6组机动试验结果表明:采用预报钟差策略在快速恢复初期的前几个小时对轨道预报的贡献尤为显著,对第1组定轨URE预报贡献最大可达84.82%。从3~8 h期间6组定轨平均情况来看,采用优化策略的预报URE,C01平均降低了26.06%,C04平均降低了31.58%,C03降低了9.95%。经测试该方法至少能将卫星不可用时间压缩1 h,对北斗系统建设具有重要工程应用价值。

Post-maneuver orbit determination based on the predicted clocks

The BDS system is designed as a GEO/IGSO/MEO mixed constellation. Satellite maintaining operation is performed every 7 to 10 days for GEO/IGSO satellites. With the maneuver satellite's status being unhealthy in the post-maneuver period, which lasts 5~6 hours, the BDS system usability is affected. In the long unhealthy periods, observation data together with satellite/station clocks are accumulated until the processed orbits meet precision requirement. To shorten the satellite's unhealthy time during post-maneuver, we propose an orbit determination method making use of the predicted satellite/station clocks. With the clocks being modeled with high precision, data of longer observation arc could be used, thus improve the orbit accuracy. In the modeling of satellite and station clocks, the reference inconsistency between the two-way satellite time frequency transfer(TWSTFT) and dynamic precise orbit determination(POD) techniques are considered. Three satellite maneuver events in November 2018 are analyzed. Results show that the satellite unavailability time could be shortened by at least 1 hour. And it improves the accuracy of orbit prediction with maximum of 84.82% for the first group of orbits in post-maneuver. For the POD from 3h to 8h after maneuver, the mean improvement of orbit prediction accuracy is of 26.06%(C01),31.58%(C04) and 9.95%(C03) by using the proposed method.