Abstract

Multi-wavelength differential absorption lidar (DIAL) can be used for remote sensing of atmospheric effluents. If the composition of a remote chemical mixture is known apriori, the wavelengths used by the multi-wavelength lidar can be directly determined via absorption cross sections. Laser lines that are absorbed by a chemical, i.e. “on-lines”, are used along with a few non-absorbed laser lines, i.e. “off-lines”. If a remote chemical mixture is unknown, then measurements are usually made with as many different laser lines as possible to reveal a chemical signature. Only after the return signals at all of these lines are processed, averaged or smoothed, does one have a chance of determining which lines were actually absorbed by the remote chemical species. This can be a lengthy process depending upon the amount of pulse averaging needed to reduce random fluctuations and noise below the level of the chemical absorption signal. Further more, the wavelength variations of the target reflectivity create a fixed spectral pattern which is imposed on the atmospheric chemical absorption spectrum.

© 1997 Optical Society of America