基于GRACE Follow-On卫星重力梯度法精确反演地球重力场

由于GRACE Follow-On双星系统等效于基线长为星间距离的一维水平重力梯度仪，因此本文基于GRACE Follow-On卫星重力梯度法开展了精确和快速反演下一代地球重力场的可行性论证研究. 研究结果表明：第一，基于GRACE Follow-On卫星重力梯度法（GFO-SGGM），利用卫星轨道参数（轨道高度250 km、星间距离50 km、轨道倾角89°、轨道离心率0.001）、关键载荷测量精度（星间距离10^-6 m、星间速度10^-7 m·s^-1、星间加速度10^-10 m·s^-2、轨道位置10^-3 m、轨道速度10^-6 m·s^-1、非保守力10^-11 m·s^-2）、观测时间30天和采样间隔10 s反演了120阶地球重力场，在120阶处累计大地水准面精度为9.331×10^-4 m. 第二，在120阶内，利用将来GRACE Follow-On双星反演地球重力场精度较现有GRACE双星平均提高61倍，因此GRACE Follow-On卫星重力梯度法是进一步提高地球重力场反演精度的优选方法. 第三，下一代GRACE Follow-On计划较当前GRACE计划的优点如下：轨道高度更低（200~300 km）、载荷精度更高（10^-7 ~10^-9 m·s^-1）和星间距离更短（50~100 km）.

Precise recovery of the Earth’s gravitational field by GRACE Follow-On satellite gravity gradiometry method

Because the twin GRACE Follow-On satellites are equivalent to the one-dimensional horizontal gravity gradiometer with a baseline length of the intersatellite range, the feasibility demonstrations on precisely and rapidly recovering the next-generation Earth's gravitational field by the GRACE Follow-On satellite gravity gradiometry method (GFO-SGGM) are carried out in this study. The research results are as follows: Firstly, based on the GRACE Follow-On satellite gravity gradiometry method, using the orbital parameters of the satellite (orbital altitude of 250 km, intersatellite range of 50 km, orbital inclination of 89° and orbital eccentricity of 0.001), the measurement precisions of key payloads (10^-6 m in intersatellite range, 10^-7 m·s^-1 in intersatellite range-rate and 10^-10 m·s^-2 in intersatellite range-acceleration by the interferometric laser ranging system, 10^-3 m in orbital position and 10^-6 m·s^-1 in orbital velocity by the GPS receiver, and 10^-11 m·s^-2 in non-conservative force by the accelerometer), a 30-day observation time and a sampling interval of 10 s, the Earth's gravitational field complete up to degree and order 120 is accurately recovered, and the cumulative geoid height error is 9.331×10^-4 m at degree 120. Secondly, in 120 degrees, the accuracy of gravity recovery from the future twin GRACE Follow-On satellites is averagely improved by about 61 times than that from the current twin GRACE satellites. Therefore, the GRACE Follow-On satellite gravity gradiometry method promisingly becomes a preferred approach for further improving the determination accuracy of the next-generation Earth's gravitational field. Finally, the advantages of the next-generation GRACE Follow-On mission as compared with the present GRACE mission principally consist of the lower orbital altitude of the satellite (200~300 km), the higher measurement accuracy of space-borne instruments (10^-7~ 10^-9 m·s^-1) and the shorter intersatellite range (50~100 km).