Passive Imaging Millimeter Wave Polarimeter System

A full Stokes, passive MMW imaging polarimeter has been designed that is capable of being deployed on an unmanned aerial vehicle. The system is a linear phased array, pushbroom system operating in the W band. In full Stokes mode, the predicted NEDT is 0.13 K, resulting in a polarimetric noise level of 0.1%; polarimetric noise of this order is shown to be required to distinguish various materials. Fewer Stokes parameters can be collected to reduce the noise level even further. The antenna will view the ground at 45a to collect Stokes imagery, but can collect at nadir for higher resolution radiometric imaging. The stringent radiometric and polarimetric calibration procedures that are required for polarimetric imaging have been developed, and the associated hardware has been designed. For Phase II, it is recommended to partially populate the systems feedhorns, amplifiers and detectors, and to demonstrate the system on a manned aircraft that will fly lower than the designed altitude. This will maintain the ground sampling distance and noise performance of the Phase III system, but with 1/4 the ground swath coverage. This system can then be fully populated once funding is secured for Phase III.