Galileo/北斗超快速轨道确定方法研究

To serve real-time and near real-time users, The International GNSS Service (IGS) began producing Ultra-rapid (IGU) GPS orbit products officially on November 3, 2000. The first 6h of recent predicted orbits show that 1D weighted RMS between IGUs from 9 ACs plus the combination and the Rapids after Helmert transformation usually falls between 2 and 5 cm. But research on Ultra-rapid Galileo/BDS orbit is little. Because of the differences on constellation, satellite configuration, ground tracking network et al, the method of Ultra-rapid orbit determination is different between GPS and Galileo/BDS. Meanwhile there are not enough real-time or hourly overseas data, which cause the difficulties of precise Ultra-rapid BDS orbit determination. So ultra-rapid Galileo/BDS orbit will be studied based on data of IGS Multi-GNSS Experiment (MGEX) and BETS network by Wuhan University over 5 years. First the final precise BDS orbit as reference for accuracy assessment will be determined. Then Galileo/BDS tracking network optimization theory will be studied. Then the project will study how the orbit prediction performance varies as a function of the arc length of the fitted observed orbits and the parameterization strategy used to estimate the empirical solar radiation pressure (SRP) effects. Next, as for the problem of lacking of real-time or hourly overseas data, methods of ultra-rapid BDS orbit determination using three kinds of global information, that is apriori orbit information, “out of date” observation data from global tracking stations or normal equations formed by those observables, and “out of date” precise orbits, have been proposed. Finally the independent software will be developed.

由于广播星历精度限制，超快速轨道成为绝大多数高精度GNSS实时导航定位的前提，多模GNSS是全球卫星导航系统发展的重要特征与优势，Galileo/北斗超快速轨道确定成为卫星导航领域和各IGS分析中心前沿热点课题。本项目利用2013-2017年IGS-MGEX跟踪网和武汉大学试验跟踪网，计算径向精度优于5cm的Galileo/北斗事后精密轨道；突破基于Taylor-Karman结构准则矩阵的网络最优化设计，基于长期轨道拟合的最佳求解弧段确定，基于时间序列、小波分析和物理特性的太阳光压模型建立和优化等关键问题，建立Galileo/北斗超快速轨道确定理论方法；针对目前无法获得足够多的实时或者few hourly国外站数据，提出基于三种不同来源的“过时”全球先验信息的北斗超快速轨道确定方法。该成果既具有重要的科学意义，又能拓展导航实时应用领域。

由于广播星历精度限制，超快速轨道成为绝大多数高精度GNSS实时导航定位的前提，多模GNSS是全球卫星导航系统发展的重要特征与优势，Galileo/北斗超快速轨道确定成为卫星导航领域和各IGS分析中心前沿热点课题。本项目按计划完成了既定的研究目标，突破了网络最优化设计、基于长期轨道拟合的最佳求解弧段确定、太阳光压模型建立和优化、全球先验信息的权函数等关键技术，完成了Galileo/BDS超快速轨道确定、基于“过时”全球先验信息的轨道确定等研究内容，并经过自主开发的超快速轨道确定软件进行了测试验证。GPS/GLONASS/Galileo/BDS四导航系统的事后精密卫星轨道上传至IGS中心MGEX组织，超快速轨道上传至全球连续监测系统iGMAS，达到了预期的研究成果。结果表明：同时考虑预报轨道精度、Helmert转换参数稳定度、太阳光压力与求解弧段关系、计算效率等因素，多GNSS超快速轨道求解弧段建议为42-45小时。在BDS零偏期间，采用CODE经验模型5参数加切向经验力和M-ABW（adjustable boxwing model）太阳光压模型，定轨精度和轨道预报精度最好。该成果既具有重要的科学意义，又能拓展GNSS导航实时应用领域。