Standoff Aerosol Plume Density and Particle Size Quantification

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): General Warfighting Requirements (GWR); Emerging Threat Reduction OBJECTIVE: The objective of this effort is to develop, calibrate, verify and validate a standoff ground-based optical system capable of measuring aerosol plume density and particle size distribution. DESCRIPTION: In order to quantify the inadvertent release of hazardous material associated with the destruction of threat chemical and biological facilities, DTRA seeks to develop a capability to remotely sense aerosol plume density and particle size distribution. Past efforts to quantify aerosol plumes have used hyperspectral imaging, single-color LIDAR, and other similar technologies. While these technologies have been used to assess plume densities, they are ill-suited to measuring particle size distribution. Quantification of both variables is essential to assessing the total potential exposure to a local population as well as to estimating how far a plume is expected to propagate in the environment. Currently, the only technique available to accurately quantify aerosol plume parameters [1] is the placement of point sensors within the envelop of a plume. However, this technique cannot be applied in most operational environments. Prior published work [2-6] has shown that some optical systems may provide the ability to estimate particle size distribution. The phase III end state of this work is to deliver an optical system to the warfighter that provides a standoff ground-based optical sensor capable of measuring aerosol plume density and particle size distribution. It should be able to measure particles in the 2-40 micron range, operate at a stand-off distance of 300 m to 3 km, and be eye safe (preferred but not required). PHASE I: Demonstrate the concept in a controlled laboratory or similar environment, identifying limits of detection related to aerosol particle sizes, aerosol concentrations, and stand-off distances. Ideally, at this scale, generating a well-characterized aerosol environment in an aerosol chamber that can achieve a steady-state condition is conducive to quantification of aerosol concentration and particle size distribution with verification and validation using several aerosol particle size and concentration point sensors inside of the aerosol chamber. The optical diagnostic capability could sample the aerosol chamber contents through opening shutters. Verification and validation should also include testing with both wet and dry aerosol particles, as well as testing under day and night time lighting conditions. The goal is to have a statistical confidence of >90% for aerosol concentration and particle size distribution demonstrated under the steady-state aerosol conditions in a controlled environment. PHASE II: 1) Develop an initial prototype system capable of operating in a field environment. 2) In an open-air controlled test, validate quantification capability against a well-characterized aerosol source by statistically determining the level of agreement with a point source ground truth sensor and having a goal of obtaining statistical confidence of >90% for aerosol concentration and particle size distribution. Quantification efforts should include comparisons within an identified aerosol region where theoretical concentrations and particle size distributions can be verified with aerosol concentration and particle size point sensors. This open air controlled aerosol region could be within a plume Taylor Cone or a Steady State regime. Several different concentrations and distances should be selected in this validation effort, to compare to the limits of detection defined in Phase I testing. Later phases of open air testing should introduce wind effects. PHASE III DUAL USE APPLICATIONS: 1) Deliver a final prototype 2) Integrated Aerosol and Vapor Applications: Validate and Verify quantitation efforts, including a full-scale test, with a DoD, DoE Laboratory or commercial partner to integrate aerosol data with Hyperspectral Imaging data sets to account for total plume mass quantification. REFERENCES: 1. Kovalev, V. Eichinger, W. (2004) Elastic Lidar: Theory, Practice and Analysis Methods. Wiley Warren, Russell & Vanderbeek, Richard & Ben-David, Avishai & Ahl, Jeffrey. (2008). Simultaneous estimation of aerosol cloud concentration and spectral backscatter from multiple-wavelength lidar data. Applied optics. 47. 4309-20. 10.1364/AO.47.004309. 2. Marchant, Christian. (2010) Retrieval of aerosol mass concentration from elastic lidar data. PhD Dissertation in Electrical Engineering, Utah State University, Logan, UT 3. Huige, Di & Wang, Qiyu & Hangbo, Hua & Li, Siwen & Yan, Qing & Liu, Jingjing & Song, Yuehui & Hua, Dengxin. (2018). Aerosol Microphysical Particle Parameter Inversion and Error Analysis Based on Remote Sensing Data. Remote Sensing. 10. 1753. 10.3390/rs10111753. 4. Jagodnicka, Anna & Stacewicz, Tadeusz & Karasi ski, Grzegorz & Posyniak, Micha & Malinowski, Szymon. (2009). Particle size distribution retrieval from multiwavelength lidar signals for droplet aerosol. Applied Optics. 48. B8. 5. Kolgotin A, M ller D, Chemyakin E, Romanov A. Improved identification of the solution space of aerosol microphysical properties derived from the inversion of profiles of lidar optical data, part 1: theory. Appl Opt. 2016 Dec 1;55(34):9839-9849. doi: 10.1364/AO.55.009839. PMID: 27958480. KEYWORDS: Lasers; Spectroscopy; Weapons; CWMD; Aerosol Plume; Agent Defeat; Optics