The GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) satellite consists of a central octagonal tube with seven internal floors that support the equipment and electronic units. Two of the floors support the gradiometer which is mounted close to the satellite’s centre of mass. The spacecraft structure is built largely of carbon-fibre reinforced plastic sandwich panels to guarantee stable conditions under greatly varying temperatures and to minimise its mass. The gradiometer structure is based on ultra-stable carbon-carbon technology.