Polarization lidar at 1.54 μm and observations of plumes from aerosol generators

The ability to detect relative changes in backscatter polarization from a scanning high-pulse-energy lidar system at 1.54-μm wavelength is demonstrated. The new capability was tested during the dissemination of various biological aerosol simulants and other particulate emissions at the U.S. Army's Dugway Proving Ground. Results demonstrate that the lidar is sensitive to different types of aerosols, and departures from the atmospheric background depolarization ratio are consistent with the limited amount of information available on the degree of particle sphericity. We conclude that the polarization-sensitive coatings of the beam-steering unit mirrors are presently the largest source of error and that this error is minimized when scanning with a near-zero elevation angle. This is an encouraging result for aerosol source surveillance applications, where the depolarization information may be useful in determining the aerosol generation mechanism or provide an additional scalar variable for use in delineating the plume from the background.