Electromagnetic formation flight for sparse aperture telescopes

The use of propellant to maintain the relative orientation of multiple spacecraft in a sparse aperture telescope such as NASA´s Terrestrial Planet Finder (TPF) poses several issues. These include fuel depletion, optical contamination, plume impingement, thermal emission, and vibration excitation. An alternative is to eliminate the need for propellant, except for orbit transfer, and replace it with electromagnetic control. Relative separation, relative attitude, and inertial rotation of the array can all be controlled by creating electromagnetic dipoles on each spacecraft and varying their strengths and orientations. This paper not only discusses optimized designs for a generic system but also shows that feasible designs exist for a five spacecraft, seventy-five meter baseline architecture for TPF.