Space-based Doppler wind lidar: Modeling of edge detection and fringe imaging Doppler analyzers

Optical, noncoherent measurement of the Doppler shift of lidar backscatter is a candidate for the measurement of atmospheric wind profiles from a satellite. Commonly called "direct detection", this method may be less difficult to implement than coherent detection systems, and can eliminate dependence on atmospheric aerosol content for Doppler wind measurements. Models presented here describe the signal shot noise limited performance of noncoherent Doppler wind lidars employing (1) location of the interference fringe of a Fabry-Perot interferometer (fringe imaging technique), and (2) measurement of the attenuation of the signal amplitude passed through the interferometer (edge technique). It is shown that there is no significant difference insensitivity between these two direct detection techniques. The minimum receiver optical aperture required of a lidar system for space-based tropospheric wind profiling in order to meet moderately demanding spatial resolution and Doppler accuracy requirements is found to be about 2 meters, a size which may be practical with the development of deployable optical telescopes. The etalon working aperture required to match this telescope is found to be a reasonable 100 mm for the fringe imaging technique, but an impossible 500 mm for the edge technique. The edge technique etalon must also be retuned in a few milliseconds in order to observe both the outgoing laser pulse and the atmospheric signal pulse, while the fringe imager etalon can observe both at a static setting. In the absence of any performance advantage, the use of the edge technique for the spaceflight Doppler wind sounder is difficult to justify. (C) 2000 COSPAR. Published by Elsevier Science Ltd.