The Methods And Numerical Simulations For Gravity Field Recovery From Satellite-to-Satellite Tracking Data

This thesis has mainly studied the methods and algorithms of recovering earth's gravity field from satellite-to-satellite tracking (SST) data and given the numerical simulations. The main works and results of this dissertation can be summarized as follows: 1)The usually frame of reference and their translations in the computation of gravity recovery are given and the spherical coordinate representation formulas of geopotential function's first and second derivatives are derived. Finally,we provide a kind of recursion algorithm and its improvement in computing fully normalized associated Legendre functions. 2)Three methods for gravity field recovery are mainly studied from the views of observation equation, (1) numerical differential method, (2) energy balance approach, (3) numerical integration method. The observational equations have been derived using the three methods above which are based on high-low SST and low-low SST observational data respectively, at the same time, the shortages and merits of these three methods are analyzed. 3)The problem of gravity field recovery can be attributed to the solution of over determined system of equations. A very efficient algorithm: preconditioned conjugate gradient method (PCCG) has been given in this paper. The selection of preconditioning matrix and the strategies of computation and storage of normal matrix are also discussed. 4 ) Numerical differential method and energy balance approach are applied respectively to recover the geopotential coefficients until 50 degree based on the simulated observation datum of CHAMP. As the results of simulation experiment demonstrate, the stability of numerical differential algorithm should be emphasized in using the first method while the precision of satellite velocity should be improved in using the latter one. 5)Energy balance approach is applied in the recovery of the geopotential coefficients until 120 degree based on the simulated observation datum of GRACE. The precision of the corresponding geopotential coefficients obtained from this method are compared with those of EGM96 and geopotential coefficients recovered from CHAMP, some analysis is given in addition.