External calibration of GOCE accelerations to improve derived gravitational gradients

The aim of ESA's satellite mission GOCE is to determine the Earth's gravity field with high accuracy and resolution. To achieve this aim, GOCE carries a gravitational gradiometer that needs calibration. Existing global gravity fieldmodels in combinationwith GOCE star sensor data may be used to synthesize reference differential accelerations with which the common and differential accelerations, as derived from the gradiometer measurements, can be calibrated. We present a new method in which the data are transformed from the time to the frequency domain, which allows accounting for the coloured noise on the measurements. The weight matrix is iteratively adjusted and we apply our method to real GOCE data. With our method, the gravitational gradient trace significantly reduces as compared with the currently available in-flight calibrated measurements.