Passive LWIR hyperspectral imaging of surfaces contaminated by CWA droplets

A passive LWIR camera based on a focal plane array detector was used to capture hyperspectral images of different scenes where low volatile chemical warfare agent (CWA) and simulant droplets were deposited on a variety of substrates. Four different CWA; mustard gas (HD), cyclosarin (GF), VX, VR, and two simulant liquids; dimethyl methylphosphonate (DMMP) and triethyl phosphate (TEP) were used as surface contaminants and applied to the substrates as 5 μl droplets. The trials were performed outdoors with the scene close to the ground and the camera imaging at an angle of approximately 35° and a stand-off distance of about 2 m, i.e., mainly the reflected radiation from the cold sky in combination with the thermal emission from the scene was observed. Brightness temperature spectra were extracted from the hyperspectral data cubes and compared to results from a thin film model as well as reference LWIR spectra of the liquids.