Drag free control for the European satellite GOCE. Part I: modelling

This paper deals with ´fine´ dynamic modeling of the European Gravity Field and Ocean Circulation Explorer (GOCE) satellite, in view of an accurate drag-free control design, outlined in a companion paper. GOCE aims at recovering with high accuracy and spatial resolution the Earth gravity field, through complementary space techniques such as gravity gradiometry and precise orbit determination. Both techniques rely on accurate attitude and drag-free control, especially in the gradiometer measurement bandwidth (5 mHz to 100 mHz), where non-gravitational forces must be compensated down to micro-Newton, and spacecraft attitude must track the local orbital reference frame with micro-radian accuracy.