SOME SIMULATED NOISE INVERSION STUDIES OF SATELLITE GEOPOTENTIAL MISSIONS INVOLVING CRITERION FUNCTIONS IN THE FREQUENCY-DOMAIN

In connection with the problem of optimally combining the results of a global geopotential mission using (1) a gravity gradiometer and (2) a n on-board GPS receiver, we propose a technique operating in the frequ ency domain using ''criterion functions'', which describe the precisio n of each inversion solution as a function of degree n and order m of its spherical harmonic expansion. We propose a formalism for term-wise averaging in the frequency domain, which is both unbiased and optimal in a global least-squares sense. Software for deriving a ''criterion function'' for the geopotential coefficient recovery errors from both GPS-tracking and gradiometry was developed This function gives a simpl e description, using a few parameters only, of the error behaviour of various observation types and geometries. Criterion functions derived for various simulated missions are described, analytically converted t o degree variance functions, and compared with results by others. For one case, criterion function dependence on mission parameters is studi ed.