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Laser Site Propagation Turbulence Profiling and Forecasting

Description:

TECHNOLOGY AREA(S): Electronics, 

OBJECTIVE: Develop and demonstrate a system for turbulence profiling from a laser ground station for propagation to ground, air, and space targets given real-time optical measurements with integrated forecasting capabilities. 

DESCRIPTION: The propagation of laser sources through the atmosphere from a ground site is affected considerably by atmospheric turbulence conditions surrounding the laser transmitter, in addition to turbulence conditions aloft. Turbulence conditions are affected by prevailing meteorological conditions in addition to local topography for the laser operating site, or at the target if located on the ground. For airborne targets, the turbulence conditions depend on the drop-off of turbulence with altitude near the ground and wind-shear conditions aloft. Propagation to space targets may involve long paths where inhomogeneous conditions exist over a range of altitudes. For laser propagation paths to ground, air, and space targets, the turbulence profile will determine the properties of atmospheric effects on laser illumination, and the ability to correct of an atmospheric channel with adaptive optics (AO) compensation systems. A system is desired for measuring existing turbulence conditions in the volume surrounding a laser installation site, as well as forecasting turbulence conditions at later times. The system may involve auxiliary sources, sensors, and platforms which work cooperatively with the ground station for turbulence profiling. 

PHASE I: Develop new approach or employ existing techniques for turbulence profiling from a ground site to ground, air, and space targets. Quantify the capabilities of the turbulence profiling method through numerical simulations. Illustrate how the measurements may be used to aid turbulence forecasting capabilities. Develop a preliminary design for field testing to be conducted during Phase II. 

PHASE II: Using the results from Phase I, develop prototype turbulence profiling hardware for use in field testing. Conduct field tests for ground and air targets out to 10 km range. Devise methods to extend operation ranges for space targets. Demonstrate the turbulence profiling and forecasting capability through field testing at an appropriate laser operating location. 

PHASE III: Military laser systems operating at ground sites will be provided environmental turbulence conditions for assessing performance limitations. Optical communication systems may be environmentally adapted for optimized performance given measured or forecast turbulence conditions. 

REFERENCES: 

1: T.C. Farrell, D.J. Sanchez, P. Kelly, A. Gallegos, W. Gibson, D. Oesch, E.J. Aglubat, A.W. Duchane, D.F. Spendel, T. Brennan, "Characterizing Earth’s Boundary Layer (CEBL)," Proc. OSA, Propagation Through and Characterization of Distributed Volume Turbulence (2014).

KEYWORDS: Communication, Lasers, Meteorology, Sensing 

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