Gravity Field Recovery by Analysis of Short Arcs of CHAMP

Abstract

The gravity field recovery strategy presented here enables the global recovery of the gravity field combined with a regional focus on geographical areas with rough gravity field features in a consistent way. The global gravity field is modeled by a series of spherical harmonics while the regional gravity field features are represented by space localizing base functions of harmonic spline type. The physical model of the orbit analysis technique is based on Newton's equation of motion, formulated as a boundary value problem in form of an integral equation of Fredholm type. The observation equations are established for short arcs of approximately 30 minutes length. The procedure can be applied either globally or regionally to selected geographical regions. For a regional application the coverage with short arcs should be slightly larger than the recovery region itself to prevent the solution from geographical truncation effects. A proper combination and weighting of the normal equations of every arc combined with a tailored regularization allows a stable solution for the field parameters. This procedure can be adapted to the roughness of the regional gravity field features, the discretization of the gravity field and the sampling rate of the observations. A global gravity field solution ITG-Champ01E has been derived based on kinematic orbits covering 360 days from March 2002 to March 2003. Regional gravity field solution have been determined for selected regions with rugged gravity field features.