GOCE Input Data: - Gradients: EGG_NOM_2 - Orbits: SST_PKI (kinematic orbits); SST_PCV (variance information of kinematic orbit positions) - Attitude: EGG_IAQ_2C - Non-conservative accelerations: EGG_CCD_2C - Data period: 01/11/2009 - 19/06/2012 No a-priori gravity field information applied (neither as reference model, nor for constraining the solution). Processing procedures: - Gravity from orbits (SST): - short-arc integral method applied to kinematic orbits, degree/order 130 - orbit variance information included as stochastic model - Gravity from gradients (SGG): - parameterization up to degree/order 250 - observations used: Vxx, Vyy, Vzz and Vxz in the Gradiometer Reference Frame (GRF) - realistic stochastic modelling by applying cascaded digital filters to the observation equations; tuned filters for 41 individual data segments - Combined solution: - addition of normal equations (SST D/O 130, SGG D/O 250) - Constraints: Kaula-regularization applied to (near-)zonal coefficients, and to coefficients of degrees/orders 181 - 250 (contraints towards zero) - Optimum weighting (SST, SGG, contstraints) based on variance component estimation. Specific features of resulting gravity field: - Gravity field solution is independent of any other gravity field information - Constraint towards zero starting from degree/order 181 to improve signal-to-noise ratio - Related variance-covariance information represents very well the true errors of the coefficients - Solution can be used for independent comparison and combination on normal equation level with other satellite-only models (e.g. GRACE), terrestrial gravity data, and altimetry - Since in the low degrees the solution is based solely on kinematic GOCE orbits, it is not competitive with a GRACE model. The processing details are presented in: Pail R., Goiginger H., Mayrhofer R., Schuh W.-D., Brockmann J.M., Krasbutter I., Hoeck E., Fecher T. (2010) Global gravity field model derived from orbit and gradiometry data applying the time-wise method. Proceedings of ESA Living Planet Symposium, 28 June - 2 July 2010, Bergen, Norway, ESA SP-686. Pail R., Bruinsma S., Migliaccio F., Foerste C., Goiginger H., Schuh W.-D, Hoeck E, Reguzzoni M., Brockmann J.M, Abrikosov O., Veicherts M., Fecher T., Mayrhofer R., Krasbutter I., Sanso F. & Tscherning C.C. (2011) First GOCE gravity field models derived by three different approaches. Jounal of Geodesy, 81:11, doi: 10.1007/s00190-011-0467-x. Mayer-Guerr T., Ilk K.-H., Eicker A., Feuchtinger M. (2005) ITG-CHAMP01: a CHAMP gravity field model from short kinematic arcs over a one-year observation period. Journal of Geodesy, 78(7-8), 462 - 480.