Improved gravitational recovery from a Geopotential Research Mission Satellite pair flying en echelon

Abstract

In the standard mission the low‐low Geopotential Research Mission (GRM) pair fly close coplanar orbits in tandem at nearly constant distance and with a fixed mutual orientation for extended periods of time. Sensitivity to the gravity field is predominantly along‐track at a single altitude. Increased geopotential accuracy and discrimination can be obtained in other configurations for which radial and cross‐track information are also sensed strongly. One such configuration which is only a small change from the standard has the pair flying en echelon in slightly different orbit planes. The addition of cross‐track information in this approach is shown to yield considerable improvement in the geopotential, especially in near‐sectorial terms. Overall field accuracy is estimated to almost double with plane separations of only a few tenths of a degree (permitting fixed antenna operation). Many near‐sectorial terms show gains of up to an order of magnitude over the equivalent standard mission. These benefits are particularly important for low‐degree terms (l < 6) expected to show significant changes in the GRM lifetime due to past and present glacial activity.