<title>Prospects for mm-wave aperture synthesis from spaceborne and aerial platforms</title>

Abstract

Passive imaging using mm-waves offers very significant advantages in scientific and military surveillance. However, the relatively long wavelengths mean that for the resolutions that are sought, the input aperture of the imager needs to be quite large, typically in excess of one meter. Deployment of conventional dish antennas of these dimensions on aircraft and in Low Earth Orbit is highly problematic. The use of snapshot synthetic aperture interferometric radiometry (SAIR) offers an attractive route to integrating a two-dimensional antenna array into the structure of an aircraft so that the transverse dimensions of the antenna can be almost as large as the aircraft. We report here a study into the feasibility of deployment of a SAIR on unmanned airborne vehicles and the achievable performance parameters. The critical considerations are the achievement of acceptable sensitivity and angular resolution from a SAIR that does not require excessive complexity. It is shown that traditional approaches based on fully sampling the spatial frequencies in the scene are unable to simultaneously meet all of these criteria, but a that a SAIR based on thinned sampling of the spatial frequencies shows promise.