GRACE地球重力场模型局部参数解算方法的研究

With the wide application of the GRACE gravity field model and the increasing demand for the Earth's gravity field model in high precision, it is of great significance to optimize the Earth's gravity field model solution method. The solution method of arc-specific parameter is a critical factor influencing the accuracy and efficiency of the Earth's gravity field model. In this project, we use on-board GPS and K-band range-rate observation of GRACE by dynamic method to obtain Earth's gravity field model and GRACE orbits. In this process, we study the solution method of arc-specific parameter, such as the initial state vector of satellites, accelerometer parameter, KBR empirical parameter, receiver clock error of LEO and the ambiguity of GPS phase observation. And a correlation analysis between the arc-specific parameters and the Earth's gravity field model parameters is proposed to study the solution method of arc-specific parameters. By comparing the time-variable gravity field model coefficients and regional time-variable signals, the effects of different arc-specific solution methods on the accuracy of the Earth's gravity field model are quantitatively analyzed and their dependence on the a priori Earth's gravity field model is determined. Finally, the solution method for effectively improving the accuracy and efficiency of the Earth's gravity field model and not relying on the prior earth gravity field model is obtained. This project has scientific significance for improving the accuracy of the Earth's gravity field model. On the other hand, the solution put forward by this project has significant application value for China's forthcoming gravity satellites.

随着GRACE地球重力场模型的广泛应用和对其精度的要求逐渐提升，优化地球重力场模型解算方法具有重要的意义。局部参数的解算方法是影响解算地球重力场模型精度和效率的关键因素。本项目拟联合GRACE星载GPS和KBR星间测速观测数据,在采用动力学积分法解算地球重力场模型和卫星精密轨道的过程中，提出从局部参数与地球重力场模型参数之间的相关性分析出发，研究初始轨道参数、加速度计参数、KBR经验参数、GPS相位模糊度和低轨卫星接收机钟差等局部参数的解算方法。通过对比特征阶次时变重力场模型系数和区域时变信号等计算结果，量化分析不同局部参数解算方法对地球重力场模型精度的影响及其对先验地球重力场模型的依赖性。最终得到有效提高地球重力场模型精度和效率，且不依赖先验地球重力场模型的解算方法。本项目对提高解算地球重力场模型精度具有科学意义，另一方面本项目提出的解算方法对我国即将发射的重力卫星具有重要的应用价值。

随着地球重力场模型的广泛应用和对地球重力场模型精度的要求逐渐提升，优化地球重力场模型解算方法具有重要的意义。局部参数的解算方法是影响解算地球重力场模型精度和效率的关键因素。本项目联合GRACE星载GPS和KBR星间测速观测数据,在采用动力学积分法解算地球重力场模型和GRACE卫星精密轨道的过程中，研究局部参数（加速度计参数和KBR经验参数等）的解算方法和策略。通过对比不同的局部参数的解算方案，最终确定最优的解算方法和策略；GRACE官方机构于2018年底发布了最新的Level1B RL03观测数据，且观测数据精度有所提高。因此本项目采用了最新的Level1B RL03观测数据基于优化的解算策略获得了最新的时变重力场模型和低轨卫星精密轨道。解算的时变重力场模型比上一代时变重力场模型信噪比有了提高。与官方机构最新发布的CSR06/GFZ06/JPL06模型精度相当。同时本项目具体量化分析了不同的Level1B观测数据对提高地球重力场模型精度的贡献，得到KBRR观测数据精度是提高时变重力场模型精度的关键。最后本项目又研究了低轨卫星精密定轨过程中，PCV建模和卫星姿态信息对高精度的卫星轨道的影响。本项目为同时解算时变重力场模型和低轨卫星精密轨道提供了参考的解算方法和策略。同时本项目形成了一套自主的卫星重力数据处理软件，可以为我国的重力卫星数据处理提供软件和技术支持。