Turbulence of the upper atmosphere and isoplanatism.

We report the results of 1,049 measurements of the vertical profile of optical turbulence as recorded by a scintillometer above a site at White Sands Missile Range. The distributional law for these measurements is shown to be approximately log normal and examples of monthly to hourly variations in profile structure are presented. An estimate is formed for the isoplanatic angle for wave propagation through each profile by calculating its five-third moment. The ensemble of these calculations is found to be log normally distributed with a mean of 7.2 microrad at a wavelength of 0.5 microm. A strong temporal correction is observed between the size of the isoplanatic angle and the intensity of scintillations. We develop a theory based upon aperture averaging to account for this phenomenon and propose the use of scintillometry to make direct measurements of isoplanatism.