基于北斗星间链路的卫星自主导航可行性分析

Feasibility Analysis of Autonomous Orbit Determination of BDS Satellites with Inter-Satellite Links

    摘要
  • 摘要: 北斗三号卫星导航系统（BeiDou-3 navigation satellite system, BDS-3）在BDS-2基础上，设计实现了高速宽带星间链路网络，以期实现导航和通信的一体化建设，并为卫星自主定轨(autonomous orbit determination, AOD)技术的实现积累宝贵的实测数据。首先, 利用星间链路数据建立分布式AOD模型；然后, 利用实测的BDS-3星间链路数据，分析了18颗中圆轨道（medium Earth orbit, MEO）卫星间的建链有效率、星座构型及星间测量噪声，并讨论了轨道初值、滤波处理间隔等因素对AOD精度的影响；最后, 给出了基于北斗三号系统18颗MEO卫星星间测距数据的AOD结果，用事后精密轨道产品对其进行了评估分析。结果表明：(1)BDS-3星间链路运行稳定，每颗卫星基本可维持9条左右的星间双向测距链路，星间有效链路数和星座布局已能够支撑实现分布式导航星座的AOD；(2)轨道初始精度、滤波处理间隔等都会影响状态估计精度和收敛速度；(3)轨道初值位置精度为0.1 m、滤波处理间隔为60 s的条件下，AOD连续运行30天的用户测距误差(user ranging error，URE）精度约为0.48 m，有效验证了分布式AOD算法的有效性。

     

    Abstract:
      Objectives  The BeiDou-3 navigation satellite system (BDS-3) has designed and implemented a high-speed broadband inter-satellite link (ISL) network on the basis of the BDS-2 to carry out integrated navigation and communication and accumulate valuable measured data for the autonomous orbit determination (AOD) of the satellites. With ISL data, navigation satellite systems can achieve AOD that enables satellites to update their ephemeris on-orbit without the support of the operational control segment. However, the key technologies of the AOD system of global positioning system have not been disclosed. In the last few years, some domestic scholars have carried out some useful research and exploration into AOD with simulation data. But the results of applying the ISL to AOD are still relatively few.
      Methods  The AOD processing model was briefly reviewed on the basis of inter-satellite ranging observations, and a distributed AOD model was built with ISL data. Then, the link building efficiency, constellation geometry, and inter-satellite measurement noise of the 18 medium Earth orbit (MEO) satellites in the BDS-3 constellation were analyzed, and the influences of the initial orbit accuracy and filtering processing interval on the AOD process were also analyzed. Finally, the AOD results obtained via the measured inter-satellite ranging data on the 18 MEO satellites were given and compared with the results of the precision orbit for evaluation and analysis.
      Results  AOD processing and performance analysis are conducted. The analysis results are as follows: (1) The BDS-3 ISLs are rather stable, with about 9 inter-satellite two-way ranging links for each satellite, and the effective ISLs and the constellation geometry could support the AOD of the distributed navigation constellation. (2) The initial orbit accuracy and the filtering interval affect the state evaluation accuracy and convergence velocity. (3) When the initial orbit accuracy is 0.1 m and the filtering interval is 60 s, the user ranging error accuracy of AOD for 30 days is 0.48 m.
      Conclusions  The results confirm the validity of the proposed distributed AOD algorithm.

     

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