Optical Methods for Turbulence Profile Determination

Accurate estimates of the profile of atmospheric turbulence strength along the path is required to improve the performance of adaptive optics systems designed to compensate the degradation effects of turbulence on directed energy systems, in astronomy, and in laser communication systems. We propose a novel technique for remote determination of the atmospheric turbulence profile along the path using laser guide star technology. The corresponding optical sensor uses a pulsed laser and a range-gated focal plane array. It samples turbulence simultaneously in many locations along the path and can operate in the presence of strong scintillation. Spatial resolution is equal to or less than 10% of the total atmospheric path. Temporal resolution, or turbulence profile update rate, is 60-100 sec. The corresponding sensor can be used for turbulence profile measurements between two points on the ground, or from ground to space, or to an aircraft along a slant path. In the Phase I program we will do a performance analysis and preliminary sensor design, develop a reconstruction algorithm for a turbulence profile determination from the optical measurements, validate the proposed approach in simulation, and develop a plan for the field demonstration in Phase II.