Interferometric Imaging for Deep Space Asset Monitoring

Technical progress in the areas of post processing and adaptive optics wavefront compensation have enabled routine high resolution imaging of satellites in low earth orbit using ground based telescopes. However, the requirement to ascertain and monitor the status of spacecraft operating in orbits extending out to geostationary altitude presents an extremely complex imaging problem for which there is no demonstrated technical solution(s). Very high angular resolution at such extreme ranges generally requires the implementation of synthetic aperture techniques which, in turn, generate very demanding operational requirements in the areas of low-light-level array aperture co-phasing and adequate spectral sampling for imaging. As an example, geostationary satellites may range from the equivalent of a stellar visual magnitude of 10 to considerably fainter while possessing angular subtenses as seen from the ground on the order of a fraction of a milliradian. The Deep Space Surveillance Branch of the Phillips Laboratory has been studying the application of adaptive optics technology designed to enable low-light-level co-phasing of optical interferometric arrays as well as the number and configuration of array apertures required for good imagery. We find that it is possible in principle to modify or upgrade a variety of the optical interferometer programs being planned or in development to a level where this mission can be enabled.