Dedicated gravity field missions––principles and aims

Current knowledge of the Earthʹs gravity field and its geoid, as derived from various observing techniques and sources, is incomplete. Within a reasonable time, substantial improvement can only come by exploiting new approaches based on satellite gravity observation methods. For this purpose three satellite missions will be realised, starting with CHAMP in 2000, followed by GRACE in 2002 and GOCE in 2004. Typical for all three missions is their extremely low and (almost) polar orbit, continuous and three-dimensional tracking by GPS and their ability to separate non-gravitational from gravitational signal parts. A further amplification of the gravity signal is achieved by inter-satellite tracking between two low orbiters in the case of GRACE and by gravity gradiometry in the case of GOCE. The rationale of GOCE will be discussed in more detail. The missions have a wide range of applications in solid Earth physics, oceanography, ice research, climatology, geodesy and sea level research.