An essential milestone in the development of lidar for biological aerosol detection is accurate characterization of agent, simulant, and interferent scattering signatures. MIT Lincoln Laboratory has developed the Standoff Aerosol Active Signature Testbed (SAAST) to further this task, with particular emphasis on the near-and mid-wave infrared.Spectrally versatile and polarimetrically comprehensive, the SAAST can measure an aerosol sample's full Mueller Matrix across multiple elastic scattering angles for comparison to model predictions. A single tunable source covers the 1.35-5 m spectral range, and waveband-specific optics and photoreceivers can generate and analyze all six classic polarization states. The SAAST is highly automated for efficient and consistent measurements, and can accommodate a wide angular scatter range, including oblique angles for sample characterization and very near backscatter for lidar performance evaluation. This paper presents design details and selected results from recent measurements.
Standoff LIDAR detection of BW agents depends on accurate knowledge of the infrared and ultraviolet optical elastic scatter (ES) and ultraviolet fluorescence (UVF) signatures of bio-agents and interferents. MIT Lincoln Laboratory has developed the Standoff Aerosol Active Signature Testbed (SAAST) for measuring polarization-dependent ES cross sections from aerosol samples at all angles including 180° (direct backscatter) [1]. Measurements of interest include the dependence of the ES and UVF signatures on several spore production parameters including growth medium, sporulation protocol, washing protocol, fluidizing additives, and degree of aggregation. Using SAAST, we have made measurements of the polarization-dependent ES signature of Bacillus globigii (atropheaus, Bg) spores grown under different growth methods. We have also investigated one common interferent (Arizona Test Dust). Future samples will include pollen and diesel exhaust. This paper presents the details of the apparatus along with the results of recent measurements.
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