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Etude de faisabilité d'un lidar Rayleigh-Mie pour la mesure à courte distance de la vitesse de l'air de sa température et de sa densité.

Abstract : Lidar (Light Detection and Ranging) is a useful tool for determining physical and chemical properties of the atmosphere. For aeronautics it could be used as an airborne instrument to characterize the atmosphere standing ahead an aircraft. Short-range applications include turbulence detection and flight optimization. The lidar technique consists in emitting a laser beam in the atmosphere, then collecting and analysing the backscattered signal. Two kinds of signal generally coexist, that have very different spectral properties. The Rayleigh signal is backscattered from air molecules, while the Mie signal is backscattered from heavier particles like dusts and aerosols. This work aims at evaluating the feasibility of a Rayleigh-Mie lidar, able to take advantage of both kinds of signals simultaneously. The scientific goal is to measure the air speed, its temperature and its density, at short-range (20-50 m). The main point of this study concerns spectral analysis methods. We propose a system using two fringe-imaging Michelson interferometers, and compare its performance to the more classical Fabry-Perot interferometer. The feasibility of wind speed measurements by a fringe-imaging Michelson interferometer is demonstrated experimentally. To that purpose, a 355-nm lidar system has been realized, and a signal processing method for fringe analysis has been developed. We show that robust measurements can be performed in daytime, insensitive to laser frequency drifts and to thermo-mechanical disturbances of the interferometer.
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Submitted on : Wednesday, July 21, 2010 - 1:39:25 PM
Last modification on : Friday, June 26, 2020 - 2:00:02 PM
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Nicolas Cezard. Etude de faisabilité d'un lidar Rayleigh-Mie pour la mesure à courte distance de la vitesse de l'air de sa température et de sa densité.. Optique [physics.optics]. Ecole Polytechnique X, 2008. Français. ⟨pastel-00004485⟩

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