A study of tunable laser techniques for remote mapping of specific gaseous constituents of the atmosphere

A comparative study has been made of three laser methods of remotely mapping three atmospheric constituents. It has been found that for NO₂, SO₂ and I₂ Differential Absorption and Scattering has a greater range and sensitivity than Laser-Induced Fluorescence, whilst for SO₂ both techniques are superior to Raman backscattering. However, the sophistication and the difficulty of interpretation associated with the former system indicates that Laser-Induced Fluorescence might be the most suitable technique in a number of situations. In particular, the Fluorescence technique appears to be well suited for mapping of localized sources of specific molecules in the 100 to 1000 m range. An analysis of the fluorescence return signal expected from a localized source has indicated that above a certain peak concentration a distortion of the returned signal could lead to a misinterpretation of both the range and concentration of the source.