IfE_GOCE05s is a GOCE-only global gravity field model, which was developed at the Institut für Erdmessung (IfE), Leibniz Universität Hannover, Germany. The observations with a time span from 1 November 2009 to 20 October 2013 are used for the model recovery. The GOCE precise kinematic orbit with 1-s sampling rate is processed for the gravity field up to degree/order 150, while the three main diagonal gravity gradients are down-sampled to 2 s and used to recover the model up to degree/order 250. With two additional Kaula’s regularizations, the combined model “IfE_GOCE05s” is derived, with a maximum degree of 250. To develop IfE_GOCE05s, the following GOCE data (01.11.2009 - 20.10.2013) was used: Orbits: SST_PKI_2, SST_IAQ_2; Gradients: EGG_GGT_2, EGG_IAQ_2. None any priori gravity field information was used.

Processing procedures:Gravity from orbits (SST): Acceleration approach was applied to the kinematic orbit data; PKI data was at 1 s sampling rate; Model was derived up to d/o (degree/order) 150; VCM (Variance-Covariance Matrix) was derived arc-wisely from the post-fit residuals.Gravity from gradients (SGG): Gradients Vxx, Vyy and Vzz in the GRF (Gradiometer Reference Frame) were used; Gradients were down-sampled to 2 s; Model was derived up to d/o 250; VCM was estimated arc-wisely from the post-fit residuals.Regularization: A strong Kaula-regularization was applied to constrain the (near-)zonal coefficients that are degraded by the polar gap problem; A slight Kaula-regularization was applied to improve the signal-to-noise ratio of the coefficients between d/o 201 and 250; The regularization parameters were empirically determined.Combined solution: The normal equations for SST and SGG were summed wih proper weighting factors; Weighting factors for SST and SGG were determined from variance component estimation; A direct inversion was applied on the final normal equation.