Single-Particle, Angular Light-Scattering Apparatus for Aircraft Sampling

MSP Corporation proposes to develop a single-particle Multi-angle Light-Scattering (MLS) spectrometer for use on board an aircraft to measure the phase function, sphericity, and size of individual aerosol particles from 0.3 um to 15 um. Phase function willbe measured from 10o to 170o using a 32-channel multiple-anode photomultiplier (PMT) and a diode-pumped green laser at 532 nm wavelength; the sphericity, by measuring the uniformity of the scattered radiation with eight fiber-optic probes with individualPMT detectors spaced around the optical axis; and the particle size and refractive index, by data analysis of the scattering signals.During each flight campaign, the instrument can be used to measure the single-particle phase function and calculate the phase function of the sampled air volume to compare with remote sensing data from satellites or ground-based LIDAR systems. The measuredsphericity will allow droplets to be distinguished from irregular-shaped particles, such as mineral dust, sea salt crystals, etc.The proposed project will lead to the development of a prototype device for bench-top testing and an operational instrument for delivery to the Naval Post-Graduate School's Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) inMonterey, California for field trials in their atmospheric research program. The proposed single-particle Multi-angle Light Scattering (MLS) spectrometer will be one of the most advanced aerosol characterization instruments ever developed. The initial application will be for aerosol measurement on-board aircrafts for use inprograms funded by ONR, NASA, NOAA and other federal agencies for global warming and climate research, and their counterparts in Europe and Asia. With modifications, a ground-based instrument can be developed to appeal to the larger community of scientistsinvolved in air pollution and health effect studies funded by EPA, DOE and other federal and state agencies such as the California Air Resources Board. The ground-based instrument will provide the measurement community with capabilities hither-to-foreunavailable, or available only in bulky laboratory prototypes constructed by individual investigators. The instrument will enable the optical characterization of aerosols to go beyond the traditional size analysis by pulse-height to the more sophisticatedangular light-scattering based measurement to determine phase function, shape, refractive index, and particle size. The development will open up new measurement possibilities and place this advanced measurement tool in the hands of the average user in asmall, modern, user-friendly package for aerosol and material characterization in scientific research and industrial application.