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Dr. Kevin RepaskyAssistant Professor, Electrical & Computer Engineering DepartmentMontana State University
“Development of an eye-safe diode laser based micro-pulse differential absorption lidar (DIAL) for water vapor and aerosol profiling in the lower troposphere”
Abstract: Researchers at Montana State University (MSU) are developing a set of lidarinstruments for remote sensing aerosol studies. Instrument in various stages of developmentat MSU include a multi-wavelength backscatter lidar, a high spectral resolution lidar, adifferential absorption lidar (DIAL) for spatially mapping carbon dioxide, and an eye-safe diodelaser based DIAL for water vapor and aerosol profiling. This talk will mainly focus on thedevelopment of the diode laser based water vapor DIAL.The diode laser based water vapor DIAL utilizes two external cavity diode lasers (ECDL),one locked to the on-line wavelength and the other locked to the off-line wavelength, toinjection seed a tapered semiconductor optical amplifier (TSOA). The output of the TSOA ispulsed by pulsing the drive current to the TSOA producing up to 7 μJ of pulse energy over a 1μs pulse duration with pulse repetition frequencies up to 10 kHz. The scattered light iscollected using a commercial 35 cm Schmidt-Cassegrain telescope with the collected lightlaunched into a multi-mode optical fiber. The return signal is monitored using an avalanchephotodiode (APD) and a multichannel scalar card. The off-line channel of the DIAL iscalibrated using the Rayleigh scattered returns above the boundary layer and the aerosolbackscatter and extinction properties are retrieved using the Fernald lidar inversion techniqueand an independent measurement of the aerosol optical depth. Water vapor number densityprofiles are retrieved using both the on-line and off-line returns and the DIAL equation.
Recent observational studies using multiple instruments including the water vapor DIAL willbe presented. During this seven day observational period, a rapid transition from a low aerosoloptical depth to higher aerosol optical depth resulting from advected biomass burning aerosolsdue forest fire smoke occurred. The characterization of the aerosol optical properties andresulting aerosol direct effect radiative forcing will be presented.
Thurday, April 14, 2011, 2:30 p.m.FL-2 Main Seminar RoomWine & Cheese Reception after Keynote