Critical issues encountered in experiments and measurements involving optical turbulence

Frank D. Eaton

doi:10.1117/12.697193

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12 February 2007 Critical issues encountered in experiments and measurements involving optical turbulence

Frank D. Eaton

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Proceedings Volume 6457, Free-Space Laser Communication Technologies XIX and Atmospheric Propagation of Electromagnetic Waves; 64570S (2007) https://doi.org/10.1117/12.697193
Event: Lasers and Applications in Science and Engineering, 2007, San Jose, California, United States

Abstract

The successful design and operation of high energy laser (HEL) and laser communication systems require a comprehensive and thorough knowledge of the real turbulent atmosphere coupled with high-fidelity realistic laser beam propagation models. To date, modeling and simulation of laser beam propagation through atmospheric turbulence have relied upon a traditional theoretical basis that assumes the existence of homogeneous, isotropic, stationary, and Kolmogorov turbulence. The real impact of the refractive index structure parameter ( C²_n ) on laser beam propagation including effects of non-classical turbulence as well as inner (l_o) and outer scale (L_o) effects will be examined. Observations clearly show turbulence is often layered and is produced by wave activity and episodic events such as Kelvin-Helmholtz instabilities. Other critical turbulence issues involve the relationship between mechanical and optical turbulence and the effect of path variability of turbulence and inner scale on optical turbulence parameters over long paths. These issues will be examined from data obtained from five systems: a) a new measurement platform using a free-flying balloon that lifts a ring with a boom upon which are mounted several fine wire (1-&mgr;m diameter) sensors to measure high-speed temperature and velocity fluctuations, b) a new system using a kite/tethered blimp platform that obtains both profile and measurements at a fixed altitude over time, c) a 50 MHz radar at Vandenberg Air Force Base that senses at high temporal and spatial resolution to 20 km ASL, d) an instrumented aircraft system, and e) a suite of optical systems. The first four systems all provide estimates of C²_n , the eddy dissipation rate (&Vegr;), l_o and L_o. Methods of calibration and problems of interpreting results from the measurement systems are discussed.

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Frank D. Eaton "Critical issues encountered in experiments and measurements involving optical turbulence", Proc. SPIE 6457, Free-Space Laser Communication Technologies XIX and Atmospheric Propagation of Electromagnetic Waves, 64570S (12 February 2007); https://doi.org/10.1117/12.697193

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