INFLUENCE OF STRATOSPHERIC TURBULENCE ON INFRARED IMAGING

We introduce a model for the power spectrum of stratospheric turbulenc e that is based on data from in situ measurements and on results of th e theory of saturated internal gravity waves. We then study the effect of that stratospheric turbulence on the scintillation and the coheren ce of starlight and on the degradation of star image. It is shown that , because the stratospheric phase structure function is approximately quadratic over a distance comparable with the aperture of a large tele scope, stratospheric turbulence does not significantly degrade short-e xposure images of star but does degrade long-exposure ones. The influe nce of stratosphere on star image degradation is more important in the IR than in the visible range because of the specific dependence of th e stratospheric coherence radius on the light wavelength. Star image m otion and blurring are determined by different characteristics of the atmosphere and cannot be explained solely on the basis of the Kolmogor ov model. The modified astronomical imaging theory predicts greater im provement in resolution as the result of tilt removal than does a conv entional theory. (C) 1995 Optical Society of America