COMPASS系统GEO卫星太阳光压模型精化技术研究

Geosynchronous earth orbit(GEO) satellites play a significant role in the COMPASS navigation system, and the errors of satellite ephemeris and clock corrections restrict the service performance of navigation system. The largest eror in sub-meter level precision orbit determination(POD) is due to the effect of solar radiation pressure(SRP), which is much larger than the MEO satellite. As being the constructing and developping phase, the GPS SRP models have been introduced in the COMPASS system. POD experiments show that the middle period and long period predicting precision need being improved. We are aiming at establishing and improving the SRP model precision for the COMPASS high orbit satellites in this project. Several kinds of observations will be employed, such as the L-band pseudoranging data, the C-band transfer ranging data, and the SLR data so on and so force. As the satellite clock offsets are obtained by the satellite-earth wireless two-way method, which could also be employed in this project. Firstly the reflectance of SRP model will be analysed both in the single and multiple POD mode, and the series characteristic will be extracted and analyzed with the wavelet method, in order to check applicability of the GPS SRP model in the COMPASS system. Relationships between the POD precision and the modelling precision will be researched and testified. Secondly we will try to design a new COMPASS SRP model , and to research on reasonable parameterization, which will consider the satellite platform and the pose data. Finally we will determine the precise orbit in each three to seven days with several kinds of observing technologies, and get a precise dynamical orbit for about 2-4 years to estimate the parameters of the new SRP model for different GEO satellites. POD experiments will be carried out to check the SRP model precision, in order to improve the model again and again.

GEO卫星是COMPASS系统的重要组成部分，其轨道测定与预报是导航服务性能的根本保证。对于亚米级定轨，光压摄动是主要误差源，是制约轨道预报精度的关键因素。COMPASS系统尚处研制阶段，其定轨借鉴了GPS光压模型，试验表明该模型并不完全适用于COMPASS系列卫星，尤其是GEO卫星。课题针对该问题，研究利用长期的各类型测轨数据，特别是所有卫星均有的、独具特色的星地时间同步与SLR数据，完成GEO卫星光压模型的设计与精化。采用小波分析法研究GPS光压模型在COMPASS系统中的应用特性，论证定轨与光压模型之间的精度关系；研究设计适合卫星平台特性的光压模型和参数表达形式，推导模型参数的法方程和参数估计方法；综合伪距、转发式测距、SLR和星地钟差等数据，完成短弧精密定轨，研究长弧精密轨道的平滑方法，并利用得到的2-4年精密轨道，估计不同卫星的模型系数，采用实测数据完成光压模型精度评估与验证。

本课题以提升COMPASS系统GEO卫星定轨与预报精度为目标，利用长期的历史数据构建了光压参数时间序列，完成了GEO卫星太阳光压模型的精化，设计并建立了GEO定轨位置精度优于1m、预报24h轨道URE优于1m的光压模型。.1）利用GEO卫星3年左右的历史实测数据，从单星和多星定轨对Box-Wing和T20模型在GEO定轨中的应用特性分别进行分析，发现了与太阳活动相关的模型参数序列的长期变化、半年变化和周日变化规律，从定轨精度方面验证评估了两种模型在正常和特殊时期（春夏秋冬）的规律，其中特殊时期卫星定轨精度衰减3倍左右。综合结果表明两种模型直接应用于GEO卫星存在一定的误差，不能完全表征太阳光压摄动特性。.2）利用GEO卫星多类型观测数据，对短弧条件下三种定轨方法进行研究，试验结果表明混合星座多星联合定轨方法精度最高，建议短弧条件下的高精度轨道确定主要以区域网条件下的多星定轨为主。提出了基于动力学平滑的高精度轨道获取方法，考虑到轨道特性及其连续性，建议采用基于3天弧长的动力学平滑法拼接长弧轨道，3天的轨道动力学平滑精度为0.74m。.3）分析了太阳光压摄动的影响因素，提出了太阳光压物理分析模型的建模方案，研究了太阳辐射压的分体建模技术，基于COMPASS卫星平台特性建立了ADBOXW模型，试验表明该模型不太适合于GEO卫星，仅适用于IGSO和MEO卫星，定轨的位置精度为14.8cm，预报24h位置精度为26.98cm。.4）设计了北斗经验Box-Wing光压模型，采用高精度事后轨道作为虚拟观测量，利用动力学平滑法重新估计模型参数，基于参数序列的特征分析，提出了在正常和特殊时期采用分弧段变模型的建模方案,并设计了力学模型补偿策略。试验表明，基于新模型GEO卫星在正常时段定轨URE由1.60m提高到0.88m，预报24h的URE由4.04m提高到1.95m；春秋分时段定轨URE由1.95m提高到1.09m，预报24h的URE由4.41m提高到2.05m。.5）设计了北斗经验BERNESE光压模型，通过对模型参数相关性分析和参数显著性检验，完成模型参数的优化选择，确定长期光压系数构建方案。试验表明，基于新模型GEO卫星的定轨位置精度由1.73m提高到0.83m，平均URE精度优于0.25m，预报24h的URE精度为0.35m，优于课题的技术指标要求。