The Standoff Aerosol Active Signature Testbed (Saast) at Mit Lincoln Laboratory

Abstract

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.

Aerosol elastic scatter signatures in the near- and mid-wave IR spectral regions

“…The optical design has been discussed more thoroughly elsewhere. 12,13 The theory of operation is shown in Figure 2. When calibrated and when combined with a particle counter, the SAAST determines the differential scattering cross section d d , and the extinction can be determined by integrating the total scatter.…”

“…12 The SAAST is both an aerosol ellipsometer and a "lidar in a box." The SAAST aerosol generation and monitoring system is currently capable of producing a wide range of wet and dry simulant and background aerosols.…”