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 μm 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
This paper presents design details and selected results from recent measurements.
Polarimetric Lidar has been recently proposed as a method for remote detection of aerosolized biological warfare
agents. Accurate characterization of the optical signatures for both biological agents and environmental interferents is a
critical first step toward successful sensor deployment.
MIT Lincoln Laboratory has developed the Standoff Aerosol Active Signature Testbed (SAAST) as a tool for
characterizing aerosol elastic scattering cross sections.1 The spectral coverage of the SAAST includes both the nearinfrared
(1-1.6 μm) and mid-infrared (3-4 μm) spectral regions. The SAAST source optics are capable of generating all
six classic optical polarization states, while the polarization-sensitive receiver is able to reconstruct the full Stokes
vector of the scattered wave. All scattering angles, including those near direct backscatter, can be investigated. The
SAAST also includes an aerosol generation system capable of producing biological and inert samples with various size
This paper discusses the underlying scattering phenomenology, SAAST design details, and presents some representative
The Standoff Aerosol Active Signature Testbed (SAAST) is the aerosol range within the MIT Lincoln Laboratory's Optical System Test Facility (OSTF). Ladar and Lidar are promising tools for precise target acquisition, identification, and ranging. Solid rocket effluent has a strong Lidar signature. Currently, calculations of the Lidar signature from effluent are in disagreement from measurements. This discrepancy can be addressed through relatively inexpensive laboratory measurements. The SAAST is specifically designed for measuring the polarization-dependent optical scattering cross sections of laboratory-generated particulate samples at multiple wavelengths and angles. Measurements made at oblique angles are highly sensitive to particle morphology, including complex index of refraction and sample shape distribution. With existing hardware it is possible to re-aerosolize previously collected effluent samples and, with online and offline diagnostics, ensure that these samples closely represent those found in situ. Through comparison of calculations and measurements at multiple angles it is possible to create a realistic model of solid rocket effluent that can be used to extrapolate to a variety of conditions. The SAAST has recently undergone a dramatic upgrade, improving sensitivity, flexibility, sample generation, sample verification, and level of automation. Several measurements have been made of terrestrial dust and other samples.
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 ES cross sections from BW simulants and interferents at all angles including 180º (direct backscatter). 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 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 SAAST apparatus along with the results of recent measurements.