Preliminary VHF radar and high-data-rate optical turbulence profile observations using a balloon-ring platform

Abstract

A recent measurement campaign at Vandenberg Air Force Base, Calif. involved taking simultaneous observations with a VHF radar and high-data-rate (1-micron diameter) platinum wires to sense optical turbulence (from temperature fluctuations). The radar observations produce profiles of the refractive index structure parameter (C 2 n ), the turbulent kinetic energy (σ 2 t ), the eddy dissipation rate (e), the inner scale (l o ), the outer scale (L o ) of turbulence, and wind speed and direction to an altitude of 20 km AGL. The fine wire measurements were taken from the surface with several sensors mounted on a balloon-ring platform sampling in excess of 3 kHz to balloon burst altitudes (typically above 25 km AGL). The main objectives of this effort are to compare the two measurement techniques and to obtain observations that can address several fundamental turbulence issues of the real turbulent atmosphere related to laser beam propagation. 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. Results presented from the radar observations include C 2 n , σ 2 t , e, l o ,and the standard deviation of vertical velocity (σ w ). A comparison of the profiles of C 2 n obtained from the two measurement techniques is shown and discussed. A time series of temperature data obtained from a fine wire probe traversing one radar range gate is presented and discussed. Future measurement and analysis efforts are presented.