一种新型重力测量卫星系统确定全球重力场的性能分析

Ability of recovering the global gravity field of a new satellite gravimetry system

本文设计了一种高-低卫星跟踪卫星、低-低卫星跟踪卫星和卫星重力梯度测量相结合的新型重力测量卫星系统,其可在一定程度上发挥卫星重力梯度和低低卫星跟踪卫星两种测量模式各自的优势.基于重力卫星系统指标设计的半解析法,深入分析了不同重力测量卫星系统配置和不同观测量及其不同白噪声水平情况下,新型卫星重力测量模式反演重力场模型的能力.数值模拟分析结果表明:在观测值精度和星间距离相同的条件下,轨道高度是影响重力场反演精度的关键因素;随着星间距离的增大,高频重力场信号反演精度会先提高后降低,轨道高度在200~350km之间时,星间距离在150~180km之间时反演精度最优;星间距离变率和卫星重力梯度两类观测值仅在某些精度配置时可达到优势互补,如果某一类观测值精度很高,则另一类观测值在联合解算时贡献非常小或者没有贡献.在300km轨道高度,若以GRACE和GOCE任务的设计指标1μm·s-1/(Hz)^(1/2)和5mE/(Hz)^(1/2)来配置新型重力测量卫星系统中星间距离变率和引力梯度观测值的精度,联合两类观测值解算200阶次模型大地水准面的精度比独立解算分别提高1.2倍和2.8倍.如果以实现100km空间分辨率1~2cm精度大地水准面为科学目标,考虑卫星在轨寿命,建议轨道高度选择300km,星间距离变率和卫星重力梯度的精度分别为0.1μm·s-1/(Hz)^(1/2)和1mE/(Hz)^(1/2).本文的研究成果可为中国研制自主的重力测量卫星系统提供参考依据.

A new satellite gravimetry mode combining SST-hl,SST-ll and SGG is proposed inthis paper.This mode can benefit from advantages of the SST-ll and SGG modes to a certain extent.The ability to recover the gravity field model using the new satellite gravimetry mode is analyzed in detail based on the semi-analytical approach used for the indicator design of the satellite gravimetry system.The different parameter settings of the gravity measurement satellite systems,different observations and corresponding different white noise levels are considered in the test.The results of numerical simulation show that the orbital height is the key factor that affects the ability of recovering the gravity field in the same condition with the same observation accuracy and inter-satellite range.With the increase of inter-satellite range,the accuracy of inversed high-frequency gravity field signal will be improved first and then decreased.And the optimal inter-satellite range is between 150 km and 180 km when the orbital height changes from200 km to 350 km.The inter-satellite range rate and the satellite gravity gradients are complementary to each other only in certain precision configurations.If the accuracy of one type of observations was very high,another type of observations would contribute not too much or don′t contribute to the combined solution.When the inter-satellite range rate observations have high accuracy,almost all frequency bands of the gravitational field model are contributed by the inter-satellite range rate of observations.At the orbit height of 300 km,when the accuracies of the intersatellite range rate and gravitational gradient observations in the new gravimetric satellite system are 1 μm·s-1/（Hz）^（1/2） and 5 mE/（Hz）^（1/2）,respectively which correspond to the design indicators of GRACE and GOCE missions,and the accuracy of the recovered gravity field model up to the degree and order 200 is 1.2 times and 2.8 times higher than the ones derived independently.In order to realize the scientific objective of 1~2 cm accuracy geoid with the 100 km spatial resolution,the proposed orbital height is 300 km in terms of the satellite operating life.And the corresponding accuracies of the inter-satellite range rate and the satellite gravity gradient are 0.1 μm·s-1/（Hz）^（1/2） and 1 mE/（Hz）^（1/2）,respectively.The research results of this paper could be a technique reference for developing the autonomous gravity measurement satellite system of China.