Passive millimeter-wave imagery of helicopter obstacles in a sand environment - art. no. 621103

Operation of military helicopters in a dusty environment challenges pilots with reduced visibility. Passive millimeter-wave (MMW) imaging has the potential to be used in these environments to image through dust cloud obscurants. The millimeter-wave phenomenology of the sand environment and the obstacles present in that environment are explored in this work. A 93 GHz polarimetric passive MMW imager was used to characterize an obstacle-rich sand environment and the results are presented. It is shown that there is a strong polarimetric signature present for both sand and cinder block between 10 and 30 degrees depression angles. Also shown is the phenomenology associated with shadows on sand. It was determined that berms and ditches can be very difficult to detect using even a sensitive MMW radiometer. The results can be used to model the performance of passive MMW imaging systems in a sandy environment.