利用先验重力场模型对GOCE卫星重力梯度观测值进行校准分析

GOCE卫星任务搭载了高灵敏度的重力梯度仪,其观测值用于恢复高精度高分辨率的地球重力场。本文利用EIGEN-5C、EGM2008、GOTIM3、GGM03S高精度全球重力场模型,确定了GOCE引力梯度张量的对角分量观测值(Vxx、Vyy、Vzz)的校准参数,分析了比例因子的稳定性,并讨论了相同模型不同阶次、同阶次不同模型以及是否估计漂移参数对比例因子、偏差参数及校准观测值的影响。研究表明比例因子的稳定性在10-4的量级,利用250阶的EIGEN-5C模型和EGM2008模型校准得到观测值的差异小于10-4 E,远远小于观测误差,以1d为周期估计校准参数时,是否估计漂移对校准结果的影响达到0.4E。同时,校准前后观测值差异的频谱说明校准过程主要影响Vxx、Vyy、Vzz观测值的低频部分,即来自先验重力场模型的中低(150)阶次,考虑到GOCE引力梯度的观测频带,校准后的观测值可用于恢复中高频的重力场信号。

Cal ibration and Analysis of SGG Observations of GOCE Based on Prior Gravity Mode l s

GOCE satel l ite carries a high-sensitivity gradiometer, whose observations are used for recovering high-precision and high-resolution earth gravity field.Based on EIGEN-5C,EGM2008,GGM03S and GOTIM3 global gravity field models,the cal ibration parameters of the diagonal components (Vxx ,V yy , V zz )of GOCE gravitational gradient tensor(GGT)were obtained.We analyzed the stability of scale factors.The influences on the calibration parameters and the calibrated observations from different gravity field models,the same model with different maximum degree and order and whether estimating the drift parameters were discussed in detail.The results shows that the stability of scale factors are about 10-4 and calibrated observations are mainly determined by the low-degree signal of gravity field models.The differences of calibrated observations between EGM2008 and EIGEN-5C up to degree and order 250 are less than 10-4 E,which is far less than the noise level of GOCE GGT.We also find that the effects of whether estimating the drift parameter on the calibrated observations could approach 0.4 E when the calibration is carried out every day.At the same time,the PSD (power spectral density)of the observation difference before and after the calibration shows that the low-frequency part of observations Vxx ,V yy ,V zz are mainly calibrated from the low-medium degree part (<150)of the empirical gravity field models.Taking the measurement bandwidth of GOCE gradiometer into account,the calibrated observations could be used for recovering the middle-high frequency signal of gravity field.