The LIDAR approach uses laser radiation to remotely observe those key parameters of the atmosphere, biosphere or hygrosphere which we have to know precisely in order to understand our earth system. Elastic or inelastic scattering of laser light rays, sometimes also in combination with absorption, is the basis for a large number of different LIDAR applications. There are different variations of the basic LIDAR principle depending on which particular physical interactions of light with the atoms, molecules or aerosol particles in the atmosphere are utilized:
The LIDAR measuring principle
Figure a) shows a typical reception signal in which four regions can be recognized:
Figure 2b) shows a typical reception signal for a measurement in homogenous fog. In order to determine the situation close to the visibility-range LIDAR, a compact instrument with a wide-angle transmission and reception cone is used. Because of the differing geometries of the two LIDAR systems, the regions 1 to 3 of figure a) are contained in the first 30 meters of figure b).