Bestimmung von Schwerefeldlösungen aus der Satellitenmission GRACE am Institut für Geodäsie der Technischen Universität Graz

The gravity field and its variations in time are important observables for the understanding of Earth’s dynamic system. The twin satellites of the GRACE (Gravity Recovery And Climate Experiment) mission have been designed to measure such temporal variations as well as the long-wavelength part of Earth’s gravity field with unprecedented accuracy on a global scale. The Institute of Geodesy at Graz University of Technology produces monthly, daily, and static gravity field solutions from raw observations of the GRACE mission for the scientific community. GRACE gravity fields derived in Graz have been used within the framework of the Climate Change Initiative (CCI) of the European Space Agency (ESA). As part of the Gravity Observation Combination (GOCO) initiative, Graz produces high-resolution static gravity fields from GRACE for combination with other satellite gravity missions such as GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) and terrestrial data. Daily solutions computed in Graz are for example used to study large flood events. This contribution gives an overview of the processing chain for GRACE gravity field recovery employed at Graz University of Technology. It comprises data preprocessing, determination of kinematic orbit positions from GPS observation, improvement of the measured satellite attitude, and the estimation of the gravity field parameters using a least squares adjustment. The functional model between the main observable – highly accurate relative velocities between the satellites – and the unknown gravity field is exemplified and an approach for the determination of the stochastic characteristics of the satellite observations is shown. To conclude, we present some applications for the GRACE gravity fields computed in Graz.