Satellite clusters for future gravity field missions

Abstract

The current missions CHAMP and GRACE have already contributed drastically to our knowledge of the Earth's gravity field in terms of accuracy, homogeneity and time- and space-resolution. The future mission GOCE will further add to that in terms of spatial resolution. Nevertheless, each of these missions has its own limitations. At the same time several geoscience disciplines push for ever higher requirements on spatial resolution, time resolution and accuracy. Future gravity field missions will need to address these requirements. A number of new technologies may enable these future missions. They include laser tracking and atomic interference. Most likely, a mission that implements such technologies, will make use of the concept of formation flying. This paper will discuss the feasibility of low-Earth satellite clusters. It focuses in particular on the stability of satellite formations under the influence of perturbations by the Earth's flattening. Depending on initial conditions several types of relative J2 orbits can be attained. By interpreting the low-low satellite-to-satellite tracking observable as gradiometry this paper furthermore indicates how satellite clusters may be employed in satellite gravimetry.