Degree-wise validation of satellite-only and combined Earth gravity models in the frame of an orbit propagation scheme applied to a short GOCE arc

The procedure of satellite orbit analysis apart from its significance in orbit dynamics can be also used as an independent assessment tool for the available Earth gravity models. The contribution of these models, which represent the main gravitational component in dynamic orbit computations, can be performed in a degree-wise cumulative sense, thus quantifying the band-limited performance of the individual models at satellite altitude. In order to demonstrate such a procedure, which can be applied as a closed assessment tool for any Low Earth Orbiter (LEO), we apply it in the frame of orbit propagation of the GOCE (Gravity Field and Steady-State Ocean Circulation) satellite. Differences of the obtained GOCE orbits are compared with the corresponding Rapid Science Orbit (RSO) data. For the contribution of the dynamic component we used the gravity models EGM2008, EIGEN-5C, GGM03S, ITG-Grace2010s and AIUB-CHAMP03S. The actual calculation of the orbit is based on the numerical integration of the equation of motion according to an 8th order Gauss-Jackson multi-step method using the predictor-corrector algorithm. The proposed scheme leads to a validation of the different gravity models, providing an insight to the effect of the gravitational counterpart to the geometry of the orbit by referring explicitly all computations to the three components of the orbital frame.