Remote Sensing of Atmospheric Turbulence by Utilizing Speckle-Turbulence Interaction and Optical Spatial Filtering

Abstract

Speckle-turbulence interaction has the potential for allowing single ended remote sensing of the path averaged strength of turbulence (structure constant, Cn2) along the line of sight to a target. If a laser transmitter is used to illuminate a diffuse object in the atmosphere, the resultant speckle field generated by the object is randomly perturbed by the atmospheric turbulence as it propagates back to the location of the transmitter-receiver. Consequently, the variance of the received intensity contains information about the strength of atmospheric turbulence. Unfortunately, the fluctuations due to speckle and those due to the turbulence cannot be separated; and therefore the variance of the received intensity cannot be used very effectively to remotely sense the strength of turbulence. However, by optically spatial filtering the received field, the strength of turbulence can be determined over three or more orders of magnitude. This will allow remote sensing of Cn2 over both horizonal and vertical paths with a relatively simple apparatus and has exciting implications with regard to global remote sensing of Cn2 from aircraft or space.