Quality Improvement of Global Gravity Field Models by Combining Satellite Gradiometry and Airborne Gravimetry

Abstract

The expected high resolution and precision of a global gravity field model derived from satellite gradiometric observations is unprecedented compared to nowadays satellite-only models. However, a dedicated gravity field mission will most certainly fly in a non-polar (sun-synchronous) orbit, such that small polar regions will not be covered with observations. The resulting inhomogeneous global data coverage, together with the downward continuation problem, leads to unstable global solutions and regularization is necessary. Regularization gives rise to a bias in the solution, mainly in the polar areas although in other regions as well.

Undoubtedly, the combination with gravity related measurements in the polar areas, like airborne gravimetry, will improve the stability of the solution. Consequently, the bias is reduced and the quality is likely to be better. Open questions are, for example, how accurate gravity anomalies must be, what spatial sampling is required, and how large the area with observations should be. Moreover, it is unknown whether measurements in one polar area only (e.g. North Pole) is sufficient.

In order to answer these questions, a gravity field solution from gradiometry-only will be compared with a solution from gradiometry combined with several airborne gravimetric scenarios. Special attention is given to the quality improvement and bias reduction relative to the gradiometry-only solution. The coefficients of a spherical harmonic series are the unknowns and their errors are propagated to, for example, geoid heights.