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Evaluation of a GOCE combination model

Sean Bruinsma(1), Jean-Charles Marty(1), Georges Balmino(1), Oleg Abrikosov(2), Christoph Förste(2) and Markus Rothacher(2)

(1) CNES, 18, avenue E. Belin, 31401 Toulouse, France
(2) GFZ, Telegrafenberg A17, 14473 Potsdam, Germany

Abstract

Numerical simulations of the gravity field parameter recovery using the direct method, with satellite positions as pseudo observations instead of simulated GPS Satellite-to-Satellite (SST) tracking data, and with gravity gradients (SGG data), were done and are ongoing in the framework of the European GOCE Gravity Consortium test and validation plan for GOCE mission data processing. The pseudo-GPS observations, containing the long wavelength gravity field signal, and the SGG measurements are processed separately because of the coloured noise in the latter. Due to this instrumental behaviour, the SGG observation equations must be filtered in order to retain only the precise information contained in the measurement bandwidth. The GOCE processing yields SST and high resolution SGG normal equations. These matrices are subsequently combined for the GOCE gravity field model adjustment and solved using Cholesky decomposition. However, the GOCE solution suffers from the polar gap in the data distribution due to the orbit inclination of 96 deg. Two general solution strategies exist to redress the model error that results from this lack of information: we may apply a regularization to the solution, or we add pertinent external data, such as GRACE and/or surface gravity data. Gravity field model solutions are computed using the simulated GOCE normal equations and either regularization is applied or additional external data (also simulated) are used. The resulting solutions are compared and evaluated.

 

Workshop poster

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