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GOCE Rapid Science Orbit Determination

Jose Van Den IJssel(1), Pieter Visser(1) and Tom Van Helleputte(1)

(1) Delft University of Technology, Kluyverweg 1, 2629 HS Delft, Netherlands

Abstract

For the GOCE satellite a Rapid Science Orbit (RSO) chain will be implemented to produce daily orbits with a 1-day latency and an accuracy of better than 50 cm, in order to support satellite operations. The RSO will be used as input for external calibration and geodetic pre-processing of the gradiometer data and for quick-look gravity field modeling.

The RSO chain provides as a baseline two orbit products, a reduced-dynamic and a kinematic solution. The reduced-dynamic solution is computed using the NASA/GSFC Geodyn s/w package and is based on a triple differenced approach, using ionospheric-free GPS phase measurements along with rapid GPS orbits computed by the International GNSS Service. The kinematic RSO solution is computed using the DLR GHOST s/w package, and is based on a zero differenced approach, using rapid GPS orbits and 30-seconds clocks computed by the Center for Orbit Determination in Europe. Both POD strategies have been extensively tested with CHAMP and GRACE data and have shown good performance.

In this paper a detailed overview will be given of both RSO POD strategies, showing results obtained with simulated GOCE receiver data. Special attention will be given to modifications that have been made for the GOCE mission, like e.g. the handling of the clock behaviour of the GOCE GPS receiver, which might show large drifts. In addition, a phase unwrapping procedure needs to be applied to the GPS observables. Finally, the reduced-dynamic POD has been tuned to take into account the anticipated behaviour of the drag-free system.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry