Since 1983, Georgia Tech, NOAA and the U.S. Army Atmospheric Sciences Laboratory have been engaged in a program whose purpose is to measure fluctuations in millimeter wave signals due to atmospheric turbulence, precipitation and fog [1,2]. Five measurement sessions have been conducted that have sampled atmospheric conditions in a variety of seasons. Frequencies of particular interest for their potential uses in higher precision imaging systems have been studied; namely, 116, 118, 142, 173 and 230GHz. These span a range of situations including windows between lines and regions near line centers. The measurements have been made over a 1.4 km path at a site near Urbana, Illinois, chosen for its exceptional flatness. It is important that the path and surrounding terrain be flat, homogeneous, and free of trees or other obstructions, so that the turbulence will not be perturbed by such irregularities. During this series of experiments, rigorous meteorological measurements have also been obtained.
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