Turbulence scale effects and resolution requirements in aero-optics.

Abstract

While optical aberrations caused by atmospheric turbulence have been extensively investigated and well characterized, recent research has identified structural differences in optical phase distortions caused by aircraft-induced, compressible turbulence. These so-called aero-optical distortions can be a critical obstacle in the development of airborne optical systems and reduce the fidelity and on-target intensity of optical beams. Using a model index-of-refraction spectrum that accounts for changes in density due to both temperature and pressure fluctuations in aero-optically active flow fields, expressions for the two-dimensional phase distortion over an aperture are developed. From these results, relations among ${{\rm OPD}_{{\rm rms}}}$, turbulent flow scales, and aperture size are examined while accounting for the effects of piston and tip/tilt corrections. Additionally, using the model spectrum, resolution requirements for wavefront sensors and numerical simulations of aero-optical flows are examined.