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A number of serious consortiums develop satellite communication networks. The objective of these communication projects is to service personal communication users almost everywhere on Earth. The intersatellite links in those projects use microwave radiation as the carrier. Free-space optical communication between satellites networked together can make possible high-speed communication between different places on Earth. Some advantages of an optical communication system over a microwave communication system in free space are: (1) smaller size and weight, (2) less transmitter power, (3) larger bandwidth, and (4) higher immunity to interference. The pointing from one satellite to another is a complicated problem due to the large distance between the satellite, the narrow beam divergence angle, and vibration of the pointing system. Such vibration of the transmitted beam in the receiver plane decreases the average received signal, which increases the bit error rate. We review: (1) the present status of satellite networks, (2) developing efforts of optical satellite communication around the world, (3) performance results of vibration effects on different kinds of optical communication satellite networks, and (4) seven approaches to overcome the problems caused by transmitter pointing vibration.

Although optical turbulence is usually modeled with micrometeorology, it is shown here that this can be done successfully too with macrometeorology using meteorological parameters measured with standard weather stations and predicted in standard weather forecasts. This makes it possible to predict C2n according to weather forecast. Two experimentally derived models are developed-one for practical use and the other for scientific understanding. Correlation of prediction with measurement is on the order of 90% or more, over large dynamic ranges of meteorological parameters. One interesting aspect of these measurements is the statistical evidence that scintillations are affected by aerosols, particularly under conditions of high total aerosol cross-sectional area. Various explanations for effects of aerosols on C2n and its measurement are suggested. In addition, validity of the models was examined, and experimental comparisons in two very different climates and surface conditions are presented. High correlation is found in both cases between prediction and measurement.

The origin and magnitude of the several kinds of background noise that perturb optical communication receivers are discussed, including background radiation sources viewed directly, radiation reflected from background objects, and radiation scattered by the atmosphere into the receiver field of view. An extensive bibliography on this topic is presented.

Beam intensity scintillations, characterized by a refractive-index structure parameter and caused by variations of macrometeorological features of the coastal atmosphere such as air temperature, wind speed and direction, and relative humidity, are examined theoretically and experimentally. In our theoretical analysis we present two well-known models considered separately for over-water and over-land atmospheric optical communication or imaging channels. By means of comparison with our experiments carried out in midland coastal environments in southern and northern Israel, we show the limitations of the models to predict the refractive-index structure C _n ² parameter for both daytime and nighttime turbulent atmospheres in different coastal zone meteorological conditions. We also present an extension of an existing model with two different practical applications that, as is shown experimentally, can be a good predictor of C _n ² for optical atmospheric paths over midland coastal zones.