Unique properties of laser radiation including its monochromatic properties, polarization, high spectral intensity, coherence, narrow beam divergence, the possibility of controlling the pulse duration and radiation spectrum and, finally, the fact that extremely high power and energy create very favorable conditions for the extensive application of lasers to communi cation systems, systems for the lidar sensing and ultra-high-precision ranging, navigation, remote monitoring of the environment, and many other systems operating in the atmosphere. The operative efficiency of the above systems depends significantly on the state of the atmosphere and the corresponding behavior of laser radia tion propagating through it. This circumstance has stimulated the studies of the above regularities during the passt 10-15 years. For the investiga tions to be carried out the scientists were forced to develop new theories and methods for studying the problem experimentally. Moreover, during such investigations some previously unknown phenomena were observed, among them the nonlinear effects accompanying high-power laser radiation propagating through the atmosphere are of paramount importance. Among the nonlinear effects caused by high-power laser radiation inter action with the atmosphere, the effects accompanying the propagation of high-power radiation through the atmospheric aerosols are of particular interest. Aerosols always occur in the atmosphere. It should be noted that the microphysical and optical characteristics of atmospheric aerosols vary widely, this fact causes a great variety in the features of their inter action with radiation."

This monograph undertakes to present systematically the methods for solving inverse problems of lidar sensing of the atmosphere, with emphasis on lidar techniques that are based on the use of light scattering by aerosols. The theory of multi-frequency lidar sensing, as a new method for studying the microphysical and optical characteristics of aerosol formations, is also pre sented in detail. The possibilities of this theory are illustrated by the experimental results on microstructure analysis of tropospheric and low stratospheric aerosols obtained with ground-based two- and three-frequency lidars. The lidar facilities used in these experimental studies were construc ted at the Institute of Atmospheric Optics S8 USSR Academy of Sciences. Some aspects of remote control of dispersed air pollution using lidar systems are also considered. A rigorous theory for inverting the data of polarization lidar measure ments is discussed, along with its application to remote measurement of the complex index of refraction of aerosol substances and the microstructure pa rameters of background aerosols using double-ended lidar schemes. Solutions to such important problems as the separation of contributions due to Rayleigh molecular and Mie-aerosol light scattering into the total backscatter are ob tained by using this theory. Lidar polarization measurements are shown to be useful in this case. The efficiency of the methods suggested here for inter preting the lidar polarization measurements is illustrated by experimental results on the investigation of the microphysical parameters of natural aero sols and artificial smokes using polarization nephelometers."

Although scarcely 20 years have passed since the creation of the first laser, laser engineering has enjoyed a variety of applications in science and in practice. Among these applications, a special pI ace is held by those related to the propagation of laser radiation in the atmosphere. Some, such as laser communication and information-transmission systems, locating and teleme tering systems, and mapping and navigation systems, require access to quantitative data on the effects of the atmosphere on the parameters of the laser beam serving as the carrier of useful information, since the efficacy of any such system depends significantly on the influence of the atmosphere. Another set of laser applications associated with the propagation of coherent radiation in the atmosphere requires the solution of both direct and inverse problems related to this complex subject. The kind of applica tion in question is the use of lasers for long-range monitoring of various physical parameters of the atmosphere-a new and highly promising direc tion in science and engineering.

Unique properties of laser radiation including its monochromatic properties, polarization, high spectral intensity, coherence, narrow beam divergence, the possibility of controlling the pulse duration and radiation spectrum and, finally, the fact that extremely high power and energy create very favorable conditions for the extensive application of lasers to communi cation systems, systems for the lidar sensing and ultra-high-precision ranging, navigation, remote monitoring of the environment, and many other systems operating in the atmosphere. The operative efficiency of the above systems depends significantly on the state of the atmosphere and the corresponding behavior of laser radia tion propagating through it. This circumstance has stimulated the studies of the above regularities during the passt 10-15 years. For the investiga tions to be carried out the scientists were forced to develop new theories and methods for studying the problem experimentally. Moreover, during such investigations some previously unknown phenomena were observed, among them the nonlinear effects accompanying high-power laser radiation propagating through the atmosphere are of paramount importance. Among the nonlinear effects caused by high-power laser radiation inter action with the atmosphere, the effects accompanying the propagation of high-power radiation through the atmospheric aerosols are of particular interest. Aerosols always occur in the atmosphere. It should be noted that the microphysical and optical characteristics of atmospheric aerosols vary widely, this fact causes a great variety in the features of their inter action with radiation."