Abstract

The DFVLR direct Laser Doppler Anemometer (LDA) is an active system using a CO₂-cw-laser for radiation source. Its output power of 5 W is focussed by a 30 cm diameter telescope into the region under investigation. Some of the radiation is backscattered by small aerosol particles drifting with wind speed through the sensing volume. The back-scattered radiation is collected by the telescope and detected by coherent techniques. In that way, the Doppler shift can be extracted which directly determines the line of sight component of the wind vector.