Precise and Rapid Recovery of the Earth's Gravity Field from the Next‐Generation GRACE Follow‐On Mission using the Residual Intersatellite Range‐Rate Method

Abstract

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 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 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 coefficients, 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 days 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.