Stabilization of satellite derived gravity field coefficients by earth orientation parameters and excitation functions

Abstract

The time variable gravity field of the Earth is determined by GRACE and SLR. Different gravity field solutions reveal some discrepancies in the low degree coefficients, especially C20. The second degree gravity field coefficients are directly related to the Earth's unknown tensor of inertia as well as the mass terms of the excitation functions, which describe the effects of atmosphere and ocean on Earth rotation. A further relationship exists between the Earth orientation parameters (polar motion and length of day), the motion terms of the excitation functions and the tensor of inertia. Up to now these interdependencies are not used for the calculation of the gravity field coefficients. They can therefore be used to validate the various parameter groups mutually. More reliable second degree gravity field coefficients can possibly be obtained if the Earth orientation parameters and the excitation functions are taken into account. This paper presents a novel method to integrate Earth orientation parameters, excitation functions and gravity field coefficients in a least-squares adjustment model with additional condition equations. This leads to consistent time series. © Springer-Verlag Berlin Heidelberg 2012.