Isoplanatic angle direct measurements and associated atmospheric conditions

Abstract

Based on aperture averaging theory, the isoplanatic patch angular extent can be measured by using scintillometry from the ground and a stellar source. An experimental calibration constant for the isoplanometer agreed within 1.5% of a mean theoretically derived calibration constant found for a broad range of optical turbulent conditions. A total of 1232 isoplanatic angle measurements was taken at the White Sands Missile Range (WSMR) and the Capistrano Test Site (CTS). A substantial decrease in the mean isoplanatic angle was found for the WSMR data (5.9 μrad) compared with the CTS results (8.7 μrad). High wind shears associated with several jet streams that occurred during the WSMR measurement period were presumed to enhance optical turbulence. Contributions of optical turbulence from the planetary boundary layer affecting the isoplanatic angle were suggested. Periodic behavior of atmosphere Cn2 is discussed as measured by high altitude Doppler radar and derived from rocket atmospheric measurements in the stratosphere and mesosphere.