The Impact of Temporal Gravity Variations on GOCE Gravity Field Recovery

Abstract

Since the main goal of the GOCE mission is the derivation of a static gravity field, significant temporal gravity changes from mass redistributions in the System Earth have to be removed from the measurement data in a dealiasing step. Furthermore, a method for gravity field recovery has to be developed, which is capable to process different kinds of data simultaneously. The effects of different mass redistribution systems, like atmosphere, oceans or hydrology, are investigated in terms of geoid and gravity gradients. Main focus is laid on hydrology effects, since global models of the continental water storage turned out to be rather inconsistent, compared to models of the other systems. However, they may benefit from the newly available GRACE gravity field models. It is shown that all time variable gravity effects are small compared with the gradiometer performance; nevertheless it is recommended to use the data from geophysical models and from monthly GRACE gravity field solutions to diminish aliasing effects in the GOCE measurements. In order to simplify the assimilation of gradiometric and satellite-to-satellite-tracking data (e.g. also from GRACE), a method for gravity field recovery has been developed, which is capable to handle the gradiometric data directly in the gradiometer reference frame. It benefits from a filter algorithm based on colored noise for the decorrelation of the gradients and applies powerful parallelization techniques. A high degree gravity field is recovered from simulated SGG data by this approach.