Log-amplitude variance and covariance of the scintillation of a diverging optical beam have been measured over a 48-hr period at a wavelength of 0.63[mu], on a 490 and 1000 m optical paths 2 m above the surface of a flat mesa near Boulder, Colorado. Simultaneous measurements of the refractive-index structure of the atmosphere have been obtained from temperature-structure-function measurements at spacings of 1, 3, and 10 cm. A saturation of scintillation occurs for values of log-amplitude variance between 0.5 and 1. After reaching a peak, the log-amplitude variance then decreases with both increasing range and increasing refractive-index turbulence. The spatial covariance of the fluctuations tends to increase in the saturation region. In the unsaturated region, the log-amplitude variance is approximately that predicted by the spherical-wave propagation theory of Tatarski.

Renewed interest in laser communication systems has sparked development of useful new analytic models. This book discusses optical scintillation and its impact on system performance in free-space optical communication and laser radar applications, with a detailed look at propagation phenomena and the role of scintillation on system behavior. Intended for practicing engineers, scientists, and students.

Several major breakthroughs have helped contribute to the emerging field of astrobiology. Focusing on these developments, this fascinating book explores some of the most important problems in this field. It examines how planetary systems formed, and how water and the biomolecules necessary for life were produced. It then focuses on how life may have originated and evolved on Earth. Building on these two themes, the final section takes the reader on a search for life elsewhere in the Solar System. It presents the latest results of missions to Mars and Titan, and explores the possibilities of life in the ice-covered ocean of Europa. This interdisciplinary book is an enjoyable overview of this exciting field for students and researchers in astrophysics, planetary science, geosciences, biochemistry, and evolutionary biology. Colour versions of some of the figures are available at www.cambridge.org/9780521875486.

In preparing the report, Astronomy and Astrophysics in the New Millenium , the AASC made use of a series of panel reports that address various aspects of ground- and space-based astronomy and astrophysics. These reports provide in-depth technical detail. Astronomy and Astrophysics in the New Millenium: An Overview summarizes the science goals and recommended initiatives in a short, richly illustrated, non-technical booklet.

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Peter Manly surveys more than 150 unusual telescopes designed by amateur and professional astronomers to suit some special need.