The GOCE satellite design optimises the gravity field sensor performance in a variety of ways. First, the effect of non-conservative forces is minimised by reducing the cross-sectional area in the flight direction. A space-first is the so-called drag-free and attitude control system, which compensates for such non-conservative forces. Third, the spacecraft has no moving parts and is extremely stiff in order to eliminate the disturbances other than the gravity field phenomena intended to be measured.