基于激光测距的卫星重力反演方法

Retrieval of the Earth’s gravity field model with high precision and high spatio-temporal resolution is the main research content of geodesy. Following GRACE satellites, research on satellite gravity recovery methods based on laser ranging has an important theoretical and practical significance to improve the spatio-temporal resolution of the gravity field model. Traditional gravity recovery methods do not consider the matching characteristics of precision among laser ranging observations, satellite orbits and high-frequency temporal aliasing error model, which failed to fully extract the gravity field information inherent in laser ranging observations. Considering the shortage of traditional gravity recovery methods, this project analyzes the impacts of high-frequency temporal aliasing errors on gravity recovery, presents a new method which expands the force models of gravity recovery with second-order of Taylor functions at geometric orbits and inserts the force models into the Newton’s equation of motion to get the accurately approximate orbits with integration, and analyzes total least squares to recover the gravity field model taking into account the effects of approximate orbital errors and high-frequency aliasing errors to the design matrix of the observational equations. The Monte-Carlo and close-loop simulation computation methods are used to analyze the ability of the new method to detect temporal gravity field model, thus providing a theoretical basis for our future satellite gravity recovery.

高精度高时空分辨率地球重力场模型恢复是大地测量学的重要研究内容，继GRACE卫星之后，研究基于激光测距的卫星重力反演方法对于提高重力场模型时空分辨率具有重要理论和现实意义。传统卫星重力反演方法没有考虑激光测距观测值与轨道及高频时变混叠误差模型的精度匹配特性，未能充分提取激光测距观测值中所蕴含的地球重力场信息。本项目通过考虑传统重力反演方法的不足，分析高频时变混叠误差对重力反演的影响，基于高精度激光测距观测值，提出将卫星重力反演的力模型在几何轨道处进行二阶Taylor展开，代入牛顿运动方程积分解算得到高精度轨道预估值；并针对轨道预估值及高频时变混叠误差对重力反演观测方程系数矩阵的影响，研究基于总体最小二乘的卫星重力反演方法；通过蒙特卡洛及闭合环路的仿真计算分析新方法探测时变地球重力场模型的能力，从而为我国未来卫星重力反演提供理论基础。

地球重力场的研究历来是大地测量学的主要任务之一，因此本项目开展GRACE卫星重力反演计算及其应用研究，为我国卫星重力任务的实施提供技术保障。本项目基于传统动力学法计算了GRACE时变地球重力场模型，其精度与国际官方机构相当；利用ERA-Interim数据计算了GRACE大气去混频模型，计算结果与GFZ的AOD1B精度相当，同时基于局部高空间分辨率的大气数据，计算了更高精度的大气去混频模型；利用GRACE时变地球重力场模型计算了地表垂直位移负荷形变，与GNSS直接量测的地表负荷形变和模型计算的负荷形变进行了详细的比较和讨论，得出了一些有意义的结论；提出了一种三维点质量法来计算GRACE探测的全球质量变化，比较了其相对传统球谐系数方法的优越性。上述研究内容和成果为卫星重力测量的相关研究提供了重要的依据和参考，也为GRACE Follow-on或NGGM重力卫星的计算及其应用提供一些有益的尝试。