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Current military and commercially fielded sensors for detection of trace materials on surfaces (explosives, narcotics, low volatility chemical warfare agents and other hazardous chemicals) require physical collection and analysis of the trace material. Although existing trace detection techniques are very sensitive, they all require unseen particles to be collected from the surface of the substrate being screened and then transferred to the analysis system. This collection process requires human input and close-proximity exposure to the screened article, which poses a safety threat from either IED detonation or hazardous chemical traces. It also introduces a fundamental limit on the screening speed, and limits the types of surfaces that can be successfully tested for trace materials to those with good “wipe-ability”. The ability to detect targets at significant standoff with a rapid, non-destructive screening technique that has sensitivity comparable to “sample and test” methods has been a “holy grail” for a number of years. Preliminary active infrared spectroscopy results from the Intelligence Advanced Research Project Activity (IARPA) Standoff ILuminator for Measuring Absorption and Reflectance Infrared Light Signatures (SILMARILS) program have shown a capability to detect trace explosives at levels comparable with Explosive Trace Detection (ETD) systems, and narcotics and chemical warfare agent simulants at similar levels. Especially interesting is the discovery that the standoff infrared technique still detects measurable explosive residue signal after solvent cleaning of surfaces, but with subtle changes in the target signature indicating a phase change from discrete particles to a thin film. Trace quantities of narcotics have been detected through plastic bags, and traces of explosives and other hazardous chemicals detected on clothing, on vehicle surfaces, on building materials, on packaging materials, and on pig skin, which is a close stand-in to human skin in terms of water, fat, and hemoglobin content. Also discussed will be test results for aerosol and fallout detection of chemical and biological simulants released in the Joint Ambient Breeze Tunnel (JABT) at Dugway Proving Grounds (DPG), as well as detection of trace surface residues at distances up to 25m.
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