Optical doppler measurement of microscale wind velocity

A system analysis of the feasibility of optical heterodyne measurement of Doppler shifts as a method for the remote determination of vector wind velocity is carried out. It is found that with a 50-mW laser at 6328 Å, naturally occurring aerosols in clear air will permit measurements at distances of only a few tens of centimeters; but haze and dust will extend this range to a few tens of meters and fog to 75 meters. By generating smoke to enhance the scatter, a range of about 40 meters will be achievable. The use of a 1-watt argon laser will extend the clear-air and smoke-plume ranges by a factor of 48 and the ranges in uniform dust or fog by smaller amounts. Hence useful measurements in the boundary layer of the atmosphere are possible although they will require some artificial contamination of the air to give consistently good results. Remote temperature measurement is not possible using this technique.