广播星历旋转误差对低轨星载BDS-3/GPS实时精密定轨影响分析

基于LT-01A卫星星载BDS-3/GPS观测值进行了星载实时精密定轨研究，并重点分析了广播星历旋转误差对实时定轨精度的影响。通过赫尔默特转换评估了所选时段内GPS和BDS-3广播星历轨道旋转误差，显示BDS-3广播星历旋转误差可达-8.7 mas,平均量级较GPS大约2.5倍。BDS-3广播星历经旋转改正后，轨道切向、法向均方根(RMS)误差从25 cm左右提升至10 cm量级，提升幅度超过50%。因此，基于星载BDS-3以及BDS-3/GPS联合的实时定轨精度受BDS-3星历旋转误差影响严重，且主要作用于切向和法向。经过旋转改正后，单独BDS-3实时定轨在切向、法向、径向RMS分别为21.0 cm、10.7 cm及11.2 cm,其切向和法向精度比改正前分别提升15.0%和31.8%;BDS-3与GPS联合定轨进一步提升切向精度至19.4 cm。得益于BDS-3广播星历较高的精度，单BDS-3以及BDS-3/GPS联合的实时定轨在旋转改正前的三维RMS分别为31.9 cm和29.2 cm,较单GPS实时定轨分别提升9.1%和16.8%;添加旋转改正后，其定轨精度分别提升至26.7 ...

Effects of broadcast ephemeris rotation error on real-time orbit determination for a low Earth orbit satellite using onboard BDS-3/GPS observations

The real-time orbit determination (RTOD) performance with onboard BDS-3 and GPS observations from a Chinese low Earth orbit satellite, LT-01A, is analyzed, with a focus on the impact of broadcast ephemeris rotation error on RTOD accuracy. The orbit rotation errors of GPS and BDS-3 broadcast ephemeris are evaluated by Helmert transformation with respect to post precise orbit product. BDS-3 broadcast ephemeris reveals rotation errors reaching up to -8.7 mas, and indicates an average rotation error about 2.5 times larger than that of GPS. After the rotation correction of BDS-3 broadcast ephemeris, the root mean square (RMS) errors in the along-track and cross-track components of BDS-3 broadcast ephemeris show significant reductions from about 25 cm to a level around 10 cm, manifesting an improvement by more than 50%. Therefore, the RTOD accuracy based on spaceborne BDS-3 and BDS-3/GPS combination are significantly affected by the rotation error of BDS-3 ephemeris, which mainly degrades the along-track and cross-track components. For BDS-3 only RTOD, the along-track, cross-track, and radial RMS errors with rotation correction are 21.0 cm, 10.7 cm, and 11.2 cm, respectively; the along-track and cross-track accuracies present improvements by 15.0% and 31.8%, respectively. By combining BDS-3 and GPS observations, the RTOD errors at the along-track components are further improved to 19.4 cm. Thanks to the high accuracy of BDS-3 broadcast ephemeris, the three-dimensional RMS errors of independent BDS-3 and combined BDS-3/GPS RTOD are 31.9 cm and 29.2 cm, respectively, which are 9.1% and 16.8% smaller than GPS-only RTOD errors, respectively. With rotation correction, the orbit determination accuracies are improved to 26.7cm and 25.0cm, respectively, which is 22.6% and 27.5% smaller than those of single GPS real-time orbit determination.