基于残余星间速度法精确和快速反演下一代GRACE Follow-On地球重力场

基于新型残余星间速度法（RIRM）反演了120阶GRACE Follow-On地球重力场. 第一，由于GPS定轨精度相对较低，通过将激光干涉测距仪的高精度残余星间速度（测量精度10^-7 m·s^-1）引入残余轨道速度差分矢量的视线分量构建了新型RIRM观测方程. 第二，基于2点、4点、6点和8点RIRM公式对比论证了最优的插值点数. 如果相关系数和采样间隔一定，随着插值点数的增加，卫星观测值的信号量被有效加强，而卫星观测值的误差量也同时增加. 因此，6点RIRM公式是提高下一代地球重力场精度的较优选择. 第三，相关系数对地球重力场精度的影响在不同频段表现为不同特性. 随着相关系数的逐渐增大，地球长波重力场精度逐渐降低，而地球中长波重力场精度逐渐升高. 第四，基于6点RIRM公式，通过30天观测数据和采样间隔5 s，分别利用星间速度和残余星间速度观测值，在120阶次处反演下一代GRACE Follow-On累计大地水准面精度为1.638×10^-3 m和1.396×10^-3 m. 研究结果表明：（1）残余星间速度观测量较星间速度对地球重力场反演精度更敏感；（2）GRACE Follow-On地球重力场精度较GRACE至少高10倍.

Precise and rapid recovery of Earth’s gravity field from next-generation GRACE Follow-On mission using the residual intersatellite range-rate method

The Earth's gravitational field from the Gravity Recovery and Climate Experiment (GRACE) Follow-On mission up to degree and order 120 is recovered based on a new residual intersatellite range-rate method (RIRM) by numerical simulation. Due to a low-precision orbit determination by the Global Positioning System (GPS), a new RIRM observation equation is created by introducing the residual intersatellite range-rate with a precision of 10^-7 m·s^-1 from the interferometric laser ranging (ILR) system into the line-of-sight (LOS) component of the residual orbital velocity difference vector from the twin satellites. The optimal number of interpolation points is comparatively demonstrated by the two-point, four-point, six-point and eight-point RIRM formulas, respectively. If the correlation coefficient and sampling interval are fixed, when the amount of signals from satellite observations is effectively enhanced with increasing the number of interpolation points, the satellite observation errors are simultaneously improved. Therefore, the six-point RIRM formula is a preferred selection for recovering the Earth's gravitational field complete up to degree and order 120. The impact of the correlation coefficient on the accuracy of the Earth's gravitational field recovery exhibits different characteristics in different frequency bands. With the gradual increase of the correlation coefficient, the accuracy of the Earth's gravitational field recovery decreases in the long-wavelength range, while it increases in the medium-long-wavelength range. The study on a comparison of influences of intersatellite range-rate and residual intersatellite range-rate measurements on the accuracies of the Earth's gravitational field recovery from GRACE Follow-On mission is conducted, which indicates that cumulative geoid height errors from GRACE Follow-On are 1.638×10^-3 m and 1.396×10^-3 m using the six-point RIRM formula, an observation duration of 30 d and a sampling interval of 5 s at degree 120, respectively. The research results show that the sensitivity of satellite gravity recovery using residual intersatellite range-rate measurements is greater than that using intersatellite range-rate measurements, and the accuracy of the Earth's gravitational field recovery from GRACE Follow-On is at least 10 times higher than that from GRACE.