北斗三号卫星两种定轨模式精度比较分析

北斗全球卫星导航系统(BDS-3)已经于2018年年底建成基本系统,并计划于2020年建成完整系统,而精确的卫星轨道是实现高性能全球服务的前提。本文基于北斗三号基本系统的18颗中圆轨道(MEO)卫星,评估了北斗三号卫星星间链路的测量噪声与测距精度,利用中国境内12个区域监测站的星地观测和星间链路观测,进行了联合卫星轨道测定试验,并与单纯区域监测站观测定轨结果进行了比较,分析了两种定轨模式重叠弧段轨道误差、轨道预报精度和激光检核精度。结果表明:北斗三号卫星的星间链路测量噪声为2.9cm,测距精度约为4.4cm;仅采用区域测站定轨,重叠弧段三维位置误差RMS为66.7cm,加入星间链路后可降低至15.4cm,提高了76.9%,24h轨道预报位置精度也由114.1cm提升至20.3cm,提升了83.2%,激光检核径向精度为8.4cm左右,明显优于北斗二号卫星轨道精度。

Comparison and analysis of two orbit determination methods for BDS-3 satellites

The basic system of BeiDou-3 (or simply called BDS-3) navigation satellite system has been completed by the end of 2018, and the whole system is planned to be completed in 2020. The precise orbit is the pre-condition of high-performance global service. The observation noise and ranging accuracy of Inter-satellite links (ISL) were analyzed based on the basic constellation of 18 satellites. The joint orbit determination experiment of the basic system was conducted based on both 12 regional stations (RS) within Chinese mainland and ISLs, and the results were compared with orbits only based on regional stations. The overlapping orbit difference (OOD), orbit prediction accuracy and satellite laser ranging (SLR) validation accuracy of both methods were analyzed. The results show that the observation noise is about 2.9 cm and ranging accuracy is about 4.4 cm. The 3D position RMS (root mean square) of ODDs for RS mode is about 66.7 cm. The accuracy of 3D position is improved by 76.9% after ISL observations are added. The 3D position accuracy of 24-hour orbit prediction can also be decreased from 114 to 20.3 cm, improved by 83.2%. The SLR validation accuracy of BDS-3 satellite orbit is about 8.4 cm, which is much better than that of BDS-2.