Enabling concepts for a dual spacecraft formation-flying optical interferometer for NASA's ST3 mission

We present the enabling concept and technology for a dual spacecraft formation-flying optical interferometer, to be launched into a deep space orbit as Space Technology 3. The combiner spacecraft makes use of a nested cat's eye delay line configuration that minimizes wavefront distortion and stores 20 m of optical pathlength in a package of \sim 1.5 m length. A parabolic trajectory for the secondary collector spacecraft enables baselines of up to 200 m for a fixed 20 m stored delay and spacecraft separations of up to 1 km.