Measurements of the Beam Wander Phenomenon in a Turbulent Medium

摘要

A collimated He-Ne laser beam at 6328 A was used to investigate the beam-wander phenomenon over a horizontal near-earth atmospheric path. Data were taken during lapse, neutral, and inversion conditions during the fall of 1969 at ranges from 350 m to 1.4 km. The total beam image at the receiver was photographically recorded at 32 frames/sec at an exposure of 1/600 sec; subsequently, each frame was scanned to find the center of energy of the beam's image. Simultaneously with the optical experiment, the wind velocity was determined at several points along the optical path to estimate the homogeneity of meteorological conditions and high-speed thermometry was used to determine the thermal structure coefficient, CT. Statistical computations and spectral analysis of the beam's center-of-energy motion and its correlation with measured meteorological quantities have been performed. Comparisons of these results with first-order theory and the wave-front angle-of-arrival problem will be presented. (Author)