Determination of gravity gradients from terrestrial gravity data for calibration and validation of gradiometric GOCE data

The satellite mission GOCE (Gravity field and steady-state ocean explorer) is the first gravity field mission of ESA's Living Planet Programme. Measurement principles are satellite-to-satellite tracking (SST) and, for the first time, satellite gravity gradiometry (SGG). To meet the mission goal of a 1-2 cm geoid at a spatial resolution of about 100 km, the satellite instruments will be calibrated in pre-flight mode and prior to the measurement phases (in-flight mode). Moreover, external calibration and validation of the measurements is performed using gravity information over well-surveyed areas. In this paper, all components of the gravity tensor are determined from terrestrial gravity data. Integral formulas based on the extended Stokes and Hotine formulas are used. It is shown that the entire tensor can be computed with an accuracy of 1.5-2.5 mE in the local North-East-Up coordinate system. In addition, the effect of white noise and a bias in the terrestrial data is studied.