Studies of millimeter-wave phenomenology for helicopter brownout mitigation

Abstract

The unique ability of the millimeter-wave portion of the spectrum to penetrate typical visual obscurants has resulted in a wide range of possible applications for imagers in this spectrum. Of particular interest to the military community are imagers that can operate effectively in Degraded Visual Environments (DVE's) experienced by helicopter pilots when landing in dry, dusty environments, otherwise known as "brownout." One of the first steps to developing operational requirements for imagers in this spectrum is to develop a quantitative understanding of the phenomenology that governs imaging in these environments. While preliminary studies have been done in this area, quantitative, calibrated measurements of typical targets and degradation of target contrasts due to brownout conditions are not available. To this end, we will present results from calibrated, empirical measurements of typical targets of interest to helicopter pilots made in a representative desert environment. In addition, real-time measurements of target contrast reduction due to brownout conditions generated by helicopter downwash will be shown. These data were acquired using a W-band, dual-polarization radiometric scanner using optical-upconversion detectors.