[G02-P] Poster

[G02-P-13] Towards the best GOCE gravity gradients

Christian Siemes, Roger Haagmans, ^○Michael Kern (European Space Agency)

The GOCE gravity gradients show perturbations that correlate with the geomagnetic field. In particular the cross-track gravity gradient is significantly perturbed in the regions around the geomagnetic poles. Recently, it was found that the perturbing effect is due to an unmodelled quadratic factor that occurs in the conversion from the electrode control voltages to accelerations, which caused the highly dynamic acceleration signal from cross-track drag to map onto the cross-track gravity gradient. Fortunately, it is possible to model and completely remove the perturbing effect, arriving at a more accurate, “clean" cross-track gravity gradient, which is demonstrated in this presentation.
Also the other gravity gradients show perturbations that correlate with the magnetic field. Those perturbations are much smaller than the perturbation of the cross-track gravity gradient, but appear systematic and are therefore important to remove as well. We will show in this presentation to which extent these perturbation can be removed from the gravity gradients by re-calibrating the accelerometer data and assess the impact on the gravity field retrieval from GOCE data.