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???????????????????????????????????????????PEM??????С????Э????????LSM????????120??GRACE???????????????????????????1??????????JPL??????GRACE???????????????????????120?????????PEM??LSM???????????λ?????????5.192??10^-10????6.633??10^-10????2????????PEM??LSM???120?????????λ???????????1?GFZ??????EIGEN-GRACE02S???????????????????????????????????????????PEM??LSM????????????????????????Ч???3?????????PEM??LSM?????????????λ????????????????????????????????????????????????????????????120??GRACE???????????????????

MUTUAL VERIFICATION OF TWO METHODS ON EVALUATING ACCURACY OF GRACE EARTH'S GRAVITATIONAL FIELD

The accuracies of GRACE Earth’s gravitational field complete up to degree and order 120 are evaluated by using the prior Earth’s gravitational field model method （PEM）and least-squares covariance method （LSM）on the basis of improved energy conservation principle，respectively.The simulative results are as follows.Firstly，based on the GRACE orbital parameters and accuracy indexes of key payload instruments，the accuracies of geopotential coefficients are 5.192×10-10 and 6.633×10-10 by using the PEM and LSM at degree 120.Secondly，simulative geopotential coefficients degree RMS errors obtained by using the PEM and LSM accord with the measured accuracy of Earth’s gravitational field model EIGEN-GRACE02S provided by German GFZ，and the validity of evaluating the accuracy of Earth’s gravitational field based on the PEM and LSM is proved.Thirdly， on the basis of coincidence of simulative geopotential coefficients degree RMS errors obtained by using the PEM and LSM，the algorithm dependability of the GRACE Earth’s gravitational field recovery complete up to degree and order 120 based on the energy conservation principle associated with the pre-conditioned conjugate-gradient iterative approach is validated adequately.