Naturally Derived Turbulence Measurement Procedures

Abstract

Atmosphere turbulence is described in terms of a general formulation that does not assume any particular form foe the turbulence structure function. Expressions are obtained for the tow-point correlation function of the complex amplitude (i.e., the atmospheric MTF) and for the more general function, the tow-point two-wavelength correlation function of the complex amplitude. A cardinal set of measurement procedures naturally derives from these two functions that enable both the integrated strength and the average structure function of the turbulence in a propagation path to be characterized. The measurement procedures are based on certain key properties of point-object images; properties that carry the essential information about the integrated effects of all mechanisms in the propagation path that affect the wavefronts. These mechanisms can include, but are not limited to, atmospheric turbulence, boundary layer turbulence, thermal blooming, telescope aberrations, and the (corrective) effects of adaptive optics. The measurement procedures enable full end-to-end characterization of the entire propagation path between object and image. They take account of amplitude scintillation as phase variation in the wavefronts. Once the entire path has been characterized, a wavelength region can be identified that leads to optimum resolution from large ground-based astronomical telescopes. For HEL system, use of optimum wavelengths leads maximum irradiance at the target and maximum target lethality range. Large performance improvements are attained by use of optimum rather than non-optimum wavelengths.