Dynamics and Control of Formation Flying Satellites

Professor Terry Alfriend, Texas A&M University, Aerospace Engineering Department

To exploit the technologies that have enabled the building of micro-satellites the Air-Force and NAsa are investigating the use of flying of numerous micro-satellites in close formation. Potential use are long baseline interferometry and large virtual antennas. The Air Force Research Lab (AFRL) technology program entitled TechSat21, scheduled for launch in 2003, is currently focusing in demonstrating the capability of the formation as a radar system for detecting ground targets. This initial demonstration will consist of three satellites forming a virtual antenna of diameter of 500-5000 km.

Initial studies have used Hill's equation for describing the relative motion of the formation for the design of potential constellations. Hill's equations are the linearized relative motion equations relative to a circular reference orbit that is orbiting a spherically symmetric Earth. The earth is not spherical, orbits are not circular and the neglected non-linear terms have some effect. Of primary concern are the gravitational perturbations, that can have a significant effect on fuel consumption. An approach for determining the effect of neglected gravitational perturbations, orbit eccentricity and non-linear terms is described and some initial results are presented.