|
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 ( C2n ) on laser beam propagation
including effects of non-classical turbulence as well as inner (lo) and outer scale (Lo) 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 C2n , the eddy dissipation rate (&Vegr;), lo and Lo. Methods
of calibration and problems of interpreting results from the measurement systems are discussed.
|
