A CONTRIBUTION TO DATA COMBINATION IN ILL-POSED DOWNWARD CONTINUATION PROBLEMS

Abstract

The spaceborne gravity field missions CHAMP, GRACE and GOCE, to be realized in the coming years, will improve our knowledge of the Earth's gravity field in the short, medium and long wavelength parts. Nevertheless, it is necessary to supplement this gravity field information with available terrestrial data. While the combination of data of different origin is comparably well-understood in well-posed problems there are some open questions in combining satellite derived and terrestrial data sets in the case of improperly posed problems. In this investigation, the future satellite missions are shortly characterized. The downward continuation process and its regularization based on Tikhonov's regularization method is reviewed. The test strategies to detect the contributions of satellite derived and terrestrial gravity field information applied in this investigation are summarized. A detailed simulation based on a GRACE-type SST mission scenario and additional terrestrial data with the task to derive parameters of a gravity field representation by local base functions is performed. The investigation tries to tackle a clarification of various questions related to the data combination by numerical tests.