Passive Infrared Detection of Liquids on Surfaces

The US Army, in support of the Joint Contaminated Surface Detector program (JCSD) program, has expressed a need to extend the advantages of wide area passive infrared sensing of chemical contaminants to the problem of detecting liquids contaminants on surfaces. A passive wide area monitoring system would allow rapid evaluation of large areas for chemical warfare (CW) contamination and provide detailed information as to position of ground contaminated with a persistent liquid. Surface CW contamination presents a serious threat both to the civilian and military sectors and an adequate defense against these weapons will require rapid detection and identification of both known and unknown agents. Recent measurements in the scientific literature suggest that passive long wave infrared sensors are capable of detecting liquids on the ground by utilizing cold sky reflectance. The physics of passive detection of liquids on surfaces is not well understood. However, the cold-sky refection drives the physics of passive detection of liquids on surfaces. A better understanding of the physics of cold-sky reflectance is needed to understand and exploit this phenomenon. The reflectivity of liquid-contaminated natural surfaces is generally not well-described using simple reflectance models. The project team seeks to explore and exploit this phenomenology.