A technique to measure optical properties of brownout clouds for modeling terahertz propagation

Abstract

Brownout, the loss of visibility caused by dust resultant of helicopter downwash, is a factor in the large majority of military helicopter accidents. As terahertz radiation readily propagates through the associated dust aerosols and is attenuated by atmospheric water vapor within short distances, it can provide low-profile imaging that improves effective pilot visibility. In order to model this application of terahertz imaging, it is necessary to determine the optical properties of obscurants at these frequencies. We present here a method of empirical calculation and experimental measurement of the complex refractive index of the obscuring aerosols. Results derived from terahertz time-domain spectral measurements are incorporated into the AFIT CDE Laser Environmental Effects Definition and Reference (LEEDR) software.

Performance evaluation of active sub-Terahertz systems in Degraded Visual Environments (DVE)

“…Previous work reported the potential use of sub-THz radiations to see through dense clouds of obscurants (e.g. sand, dust) in DVE conditions [12]. This paper reports an experimental evaluation of the obscurant penetrating capability of sub-THz waves from 400 GHz to 700 GHz.…”