Bioaerosols laser-induced fluorescence provides specific robust signatures for standoff detection

One of today's primary security challenges is the emerging biological threat due to the increased accessibility to biological warfare technology and the limited efficiency of detection against such menace. At the end of the 90s, Defence R&D Canada developed a standoff bioaerosol sensor, SINBAHD, based on intensified range-gated spectrometric detection of Laser Induced Fluorescence (LIF) with an excitation at 351 nm. This LIDAR system generates specific spectrally wide fluorescence signals originating from inelastic interactions with complex molecules forming the building blocks of most bioaerosols. This LIF signal is spectrally collected by a combination of a dispersive element and a range-gated ICCD that limits the spectral information within a selected atmospheric cell. The system can detect and classify bioaerosols in real-time, with the help of a data exploitation process based on a least-square fit of the acquired fluorescence signal by a linear combination of normalized spectral signatures. The detection and classification processes are hence directly dependant on the accuracy of these signatures to represent the intrinsic fluorescence of bioaerosols and their discrepancy. Comparisons of spectral signatures acquired at Suffield in 2001 and at Dugway in 2005 of bioaerosol simulants, Bacillius subtilis var globiggi (BG) and Erwinia herbicola (EH), having different origin, preparation protocol and/or dissemination modes, has been made and demonstrates the robustness of the obtained spectral signatures in these particular cases. Specific spectral signatures and their minimum detectable concentrations for different simulants/interferents obtained at the Joint Biological Standoff Detection System (JBSDS) increment II field demonstration trial, Dugway Proving Ground (DPG) in June 2005, are also presented.