Airborne lidar anemometry

Laser anemometry techniques have been used by researchers in laboratories and wind tunnels for many years. A first overview of these techniques existed, the subject of the previous version of the article [E 4 320] , but it dated back to 1994. This new article describes the evolution of the state of the art, in particular over the last two decades, with regard to on-board anemometry on aircraft, and considers the most likely applications.

First, we review the fundamental physical principles that drive Doppler shift measurements, either in the infrared or ultraviolet range. The principles of heterodyne detection and "single-particle" processing, the fundamental treatment enabling permanent operation to be envisaged, are described. An overview of worldwide work is then given, followed by a presentation of work at Thales. Developments in laser techniques linked to telecommunications (widespread use of "solid-state" lasers, with wavelengths around 1.5 μm) and optical component integration techniques have made it possible to simplify and miniaturize equipment to an extremely significant degree. A wide range of applications can be envisaged, both for standard aircraft anemometry, using a completely different mechanization from current systems, and for helicopter anemometry, or for calibration during flight tests. Longer-term use for measuring wind heterogeneities is also envisaged. At the same time, changes in aeronautical standards concerning the independence of components will encourage the serial use of mixed systems on transport aircraft in the medium term.