Applications of synthetic aperture radiometry

A new passive aperture synthesis technology called RADSAR offers improved high resolution imaging for airborne and spaceborne systems. To be competitive with radar, microwave radiometer instruments must simultaneously provide high thermal resolution, high spatial resolution and high area coverage. An airborne system must also achieve light weight and low aerodynamic drag. RADSAR (RADiometric SAR) is uniquely capable of meeting these requirements because it synthesizes a large aperture (to achieve high spatial resolution), achieves long integration time (for high thermal resolution) and wide field of view (for high coverage rate). It uses two linear array antennas which confer light weight and low aerodynamic drag. The two antennas generate multiple parallel fan beams in the direction orthogonal to the flight path. In the direction of night, the interferometric lobe pattern generated by the two antennas is used to measure the spatial frequency content of the scene. Correlation processing is used to recover the original spatial image. The technology offers timely all-weather, day-night, high resolution imaging and measurement of military, meteorological and environmental phenomena. In addition to describing the technology, this paper covers some of the mission requirements, compares the power available to spaceborne active and passive systems, and presents engineering and mission performance predictions for an airborne system