适应不同姿态控制模式的北斗卫星定轨方法研究

The satellite attitude control mode has an important influence on precise orbit determination (POD). The Beidou satellites have three attitude control modes, namely, yaw-steering (YS) mode, orbit-normal (ON) mode and continuous yaw-steering (CYS) mode. The measurement model and dynamic model characteristics are different in different attitude control modes. The orbit measurement model and dynamic model optimized method and POD optimized projects are hot topics at development stage of global Beidou system (BDS) for different kinds of satellites in different attitude control modes. The model error property will be analyzed and modelled. We are aiming at establishing orbit determination methods in different attitude control modes by different kinds of data in BDS. The satellite clock offsets are directly measured with two-way satellite time frequency transfer (TWSTFT), which is peculiar for BDS with high accuracy. The orbit error and satellite clock error will be separated by TWSTFT, Beidou experimental solar radiation pressure (SRP) model will be established by Beidou precise orbit lasting more than 4 years for global Beidou satellites. Inter-satellite links (ISL) technology is newly employed in new generation BDS, limit of regional network will be overcome by ISL technology, POD with ISL data will be researched. Antenna phase center correction model in CYS mode will be optimized. Orbit determination experiments by different kinds of Beidou data will be carried out in order to improve the model again and again by five kinds of orbit accuracy assessment methods, optimal orbit determination projects in different attitude control modes will be established to improve the orbit accuracy and stability for Beidou satellites.

卫星姿态偏航控制模式对定轨有重大影响，北斗卫星存在多种姿态控制模式，不同的姿控模式表现出不同的模型误差形态。如何精化不同姿控模式下测量模型与动力学模型误差以及如何优化其定轨方案是北斗全球卫星导航系统研制建设阶段值得系统研究的热点。本课题侧重不同姿控模式下模型误差的分析与建模。首先，充分利用北斗系统独有的星地双向时间同步测量技术，力求剥离钟差与卫星轨道误差，基于4年多精化后的北斗精密轨道建立满足高精度定轨的北斗经验太阳辐射压模型。其次，利用北斗系统新增的星间链路双向测量技术，克服区域地面监测网的局限，丰富测轨手段，开展星地星间联合定轨试验；精化连续动偏期间的天线相位中心修正模型。最后，基于北斗不同类型实测数据研究不同姿控模式下的最优定轨方法，通过内外符共5种精度评估方法完成定轨精度评估与方案优化，最终建立分弧段变模型的定轨方法以实现不同姿控模式下北斗卫星定轨的高精度与高稳定度。

本课题以提升北斗导航卫星的轨道精度和稳定度为目标，充分利用北斗系统独有的星地、星间双向时间同步和星间链路双向测量技术，有效分离轨道误差，突破建立适应不同姿态控制模式的北斗经验光压模型，构建分弧段变模型的北斗卫星定轨方法。北斗IGSO/MEO卫星在零偏期间定轨弧段UERE精度从优化前的几十米甚至上百米提升至1.38m。北斗IGSO/MEO卫星在连续动偏期间定轨弧段UERE精度为1.22m。北斗GEO卫星在春秋分附近时段定轨弧段UERE精度从优化前的十米提升至0.72m。.（1）分别论证了T20模型、ECOM5太阳光压模型、ECOM9太阳光压模型对不同类型卫星的定轨效果。同时提出了基于精密星历的北斗经验光压模型建模方法。研究结果表明：GEO卫星应采用ECOM9参数模型，IGSO/MEO卫星应采用T20模型进行定轨。基于北斗经验SPHERE光压模型进行单星定轨，与传统SPHERE光压模型相比，正常及春秋分时段定轨及预报弧段分别提高了1m和2m左右，该方法显著提升了GEO卫星的定轨稳定度。.（2）利用北斗系统实测星间链路数据开展了星地/星间联合定轨与自主定轨的研究，详细介绍了星间双向测距归算原理，推导了法方程叠加的星地/星间联合定轨的原理及流程，研究了基于锚固站的卫星自主定轨算法，研究结果表明：星间链路数据的加入能够提高卫星轨道的定轨精度，与仅星地链路的定轨精度相比，预报2小时弧段MEO卫星轨道URE误差从19cm提升至7cm，IGSO卫星轨道URE误差从32cm提升至25cm，GEO卫星轨道URE误差从55cm提升至44cm。.（3）详细论证了北斗GEO/IGSO/MEO卫星在动偏、零偏、连续动偏和春秋分附近的定轨策略及定轨精度，研究结果表明：对于Beidou-2卫星建议采用基于星地钟差约束下多星定轨方法和ECOM 5模型相结合的方法，UERE精度均值为1.38m。Beidou-3卫星建议采用常规多星定轨和ECOM 5模型相结合的方法，UERE精度均值为1.22m。GEO卫星在春秋分附近时段建议采用基于星地钟差约束下多星定轨方法和ECOM 9模型相结合的方法，UERE精度均值为0.72m。上述精度指标均优于课题设计指标。基于本课题提出的最优定轨策略可大幅提升零偏期间和春秋分附近时段的北斗卫星定轨精度。