Polarimetric passive millimeter-wave sensing

The U.S. Army Research Laboratory has developed a 93-GHz Stokes radiometer that is currently being used to quantify the polarimetric signature of various objects and materials. Preliminary measurements using the radiometer have been made of various terrain types and objects, which have included an asphalt aircraft runway, a gravel road, water, grass, a tank, and a truck. A description of the development of the radiometer, its performance, and some initial results are presented. These results are the first step in assessing the utility of polarimetric radiometry and specifically how missions can be enhanced using this information. The results show that polarimetric radiometry may be useful for eliminating water as a false target in the imagery. It is also shown that asphalt aircraft runways do have a polarimetric signature that is different than short dormant grass at a 3-deg glide slope angle.