GOCE: a full-gradient simulated solution in the space-wise approach

GOCE will be the first satellite gradiometric mission with the purpose of estimating the stationary gravitational field to a high accuracy and spatial resolution. The on-board gradiometer will provide measurements of the second derivatives of the gravitational potential along the instrumental axes, which are used together with the satellite tracking data to retrieve the spherical harmonic coefficients of the geopotential model. To this aim, a possible strategy is the so-called space-wise approach, basically exploiting the spatial correlation between data. This requires a pre-processing procedure consisting in filtering the observations in time and then producing grids of second derivatives and potential on a boundary sphere at mean satellite altitude. In the past, this approach was applied only to simulated second radial derivatives. A time-series of the anomalous potential along the orbit was also used in order to improve the estimate at low frequencies. In this work we aim at integrating the information coming from all the three diagonal components, as measured in the gradiometer reference frame. In particular the performance of the space-wise approach has been tested on the basis of realistic end-to-end simulated data, showing that the proposed method is able to estimate the spherical harmonic coefficients up to degree and order 200. The results have to be evaluated also taking into account the time-length of the available data, namely one month, which is critical for any space-wise approach.