Sensing refractive-turbulence profiles (C(n)(2)) using wave front phase measurements from multiple reference sources

Abstract

A new technique for sensing refractive-turbulence profiles is described. The technique is based on performing a spatial correlation of the measured wave front phase from two reference sources. This technique is unique in that the correlation properties of the wave front phase are used instead of the more common approach of using optical scintillations. The geometry between the reference sources and the two wave front sensor apertures is arranged such that the two optical paths cross at some point in front of the sensor plane. The wave front phase for each reference source is reconstructed from the measured wave front sensor data. A spatial correlation of the two reconstructed phase maps is performed. From this correlation we are able to extract a measure of the structure constant of the refractive-index fluctuations C(n)(2). The resolution of the technique depends on the angle between the optical paths, the spatial frequency response of the wave front sensors, as well as the size of the wave front sensorapertures. For sensing the vertical profile of C(n)(2), we can obtain resolution of the order of 100 m by using sources separated by 1.15 degrees .