Tropospheric Wind Profiling with Doppler LIDAR

Abstract

A coherent Doppler LIDAR system for remote sensing of atmospheric winds has been developed by Kayser-Threde GmbH. The system is devoted for meteorological airport surveillance and for atmospheric research studies. A diode- pumped Tm:YAG laser system generates eye-safe laser pulses with 3 mJ output energy, 600 nsec duration (full width half maximum FWHM) at a pulse repetition frequency (PRF) of 100 Hz. The q-switched laser is operating single longitudinal mode at 2.02184 µm wavelength, where atmospheric attenuation due to molecular absorption is low. This is achieved by injection seeding the pulsed laser with an etalon-tuned, cw Tm:YAG laser. A 10 cm aperture, offaxis Dall-Kirkham telescope is employed to expand the transmitted laser beam and to receive the atmospheric backscatter signal. This coherent LIDAR system is housed in a mobile 20’ container. On its roof, a computercontrolled, two axis mirror system is installed which allows scanning the laser beam in elevation and azimuth with a resolution of 0.1 degrees on each axis. Thus, the full hemisphere above and around the LIDAR station can be probed. The Doppler shifted frequency of the received radiation is measured using a heterodyne detection scheme and employing the cw laser as local oscillator.