New approach to estimate time variable gravity fields from high-low satellite tracking data

Abstract

Estimating the time-variable gravity field signal has become an important task in climate research. Different scientific communities rely on the produced time series of gravity field information to investigate for example ice melting, changes in water storage or the effects of heavy earthquakes. Today the only measurement system which can provide these gravity field solutions without any constraints is the satellite mission GRACE (Gravity Recovery and Climate Experiment). Therefore it would be of interest to prolong the current time series by another technology.A method to estimate the gravity field is based on the kinematic orbit positions of a satellite. These positions are determined using the Global Positioning System. This method is well known and is widely used as a supplement to other measurement technologies. But present orbit estimates are degraded by systematic effects which affect the long-wavelength components of the gravity field estimation. Especially these frequencies are of concern for investigating variations in the Earth’s gravity field. If these systematic effects are reduced it should be possible to generate a time series of gravity field solutions similar to those available today. To improve the orbit accuracy we introduce a new approach to estimate kinematic orbit positions based on raw observations. This contribution presents this method and first results based on real data.