北斗IGSO卫星姿态零偏航状态下精密定轨

Precise Orbit Determination for the BDS IGSO Satellites Under the Yaw-steering Mode

考虑到卫星平台供电和卫星安全等因素,北斗系统IGSO卫星姿态采用动态偏置与零偏置相结合的控制方式。在不同的控制模式下,卫星本体和太阳帆板受照条件存在一定的差异,动偏期间的力学模型不适用于零偏期间,零偏期间的IGSO卫星定轨精度衰减非常明显,致使重点地区系统服务平均可用性降低2%,其他地区降低4%,系统服务性能受到严重挑战。针对该问题,本文提出了钟差约束条件下的零偏状态定轨方案,设计了详细的钟差应用策略、系统差控制策略和力学模型误差补偿策略,解决了IGSO卫星零偏期间精密定轨问题,实现了动偏转零偏、零偏转动偏两个状态变化前后卫星轨道产品的"无缝衔接",导航服务未中断,卫星空间信号精度保持了连续和稳定。实测数据的试验结果表明:①C06卫星的UERE由2.95m提高为1.22m,C09卫星的UERE由6.29m提高为1.54m;②C06和C09卫星UERE小于2.5m概率分别由59.87%和35.04%提高为94.85%和88.49%,UERE小于5m概率分别由92.10%和71.67%提高为99.98%和99.43%。

Considering the energy supply and security factors,both the orbit-normal mode and the yaw-steering mode are adopted in the BDS IGSO attitude control system.The irradiation instances for the satellite body and solar panel are different for the two attitude control mode,with different dynamic models.If using the ordinary dynamic models in the precise orbit determination (POD),the POD accuracy declines seriously during the yaw-steering period.Therefore the average availability falls 2% in the BDS key service area,and 4% in the BDS total service area,the service performance faces serious challenges.A new POD strategy is brought forward with the restriction of time offsets in this paper for the BDS IGSO satellites during the yaw-steering period.The time offsets application strategy,systematic error controlling strategy,and dynamic models errors compensation strategy are designed in this paper in order to solve the BDS IGSO POD accuracy falling problem.The IGSO satellites ephemeris is consecutive for the transformations between the orbit-normal mode and the yaw-steering mode.The BDS navigation service is consecutive,with the continuous and steady space signal accuracy for the IGSO satellites.POD experiments were carried out during the BDS IGSO yaw-steering period.Results showed that the user equivalent ranging error (UERE) is improved from 2.95 m to 1.22 m for the BDS C06 satellite,and from 6.29 m to 1.54 m for the BDS C09 satellite.The ratio of UERE less than 2.5 m is improved from 59.87% to 94.85% for the C06 satellite,and from 35.04% to 88.49% for the C09 satellite.And the ratio of UERE less than 5 m is improved from 92.10% to 99.98%for the C06 satellite,and from 71.67% to 99.43% for the C09 satellite.