Spectral analysis and interpretation of current satellite-only Earth gravity models by incorporating global terrain and crustal data

The increasing number of new satellite-only and combined earth gravity models in terms of sets of potential harmonic coefficients up to a truncated maximum degree and order, that are becoming available either from the sole analysis of satellite tracking, accelerometry or gradiometry data, or from the combination of satellite data with terrestrial information and global digital elevation models for the earth’s topography/bathymetry and crustal structure, sets new challenges in the field of gravity field modeling, interpretation and analysis. Scope of the current project was to propose some means of interpretation, modeling and analysis tools which can be applied both independently and combined for the purpose of assessing and interpreting a given gravity model. The spectrum of such a model contains contributions from all the underlying sources in the earth’s interior, thus the task of analysis and interpretation should include some band-limited approach for the characterization and understanding of the distinct spectral bands of the model. The existence of digital databases for the layered representation of the crust down to the crust-mantle boundary permits in this context the forward computation of the individual contributions of these masses to arbitrary points in space, thus also at satellite altitude. The successful realization of three toolboxes, one for the CRUST 2.0 geometrical modeling and analytical computation for the induced gravity signal, one for the spectral assessment of difference models and one for the degree-wise assessment of a gravity model to the procedure of precise orbit determination, was implemented in the frame of the present project providing a geometrical and physical insight in some of the current satellite-only and combined earth gravity models.