Influence of stratospheric turbulence on infrared imaging

We introduce a model for the power spectrum of stratospheric turbulence that is based on data from in situ measurements and on results of the theory of saturated internal gravity waves. We then study the effect of that stratospheric turbulence on the scintillation and the coherence 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 telescope, stratospheric turbulence does not significantly degrade short-exposure images of star but does degrade long-exposure ones. The influence of stratosphere on star image degradation is more important in the IR than in the visible range because of the specific dependence of the stratospheric coherence radius on the light wavelength. Star image motion and blurring are determined by different characteristics of the atmosphere and cannot be explained solely on the basis of the Kolmogorov model. The modified astronomical imaging theory predicts greater improvement in resolution as the result of tilt removal than does a conventional theory.

[1]  C. Hostetler,et al.  Observations of horizontal and vertical wave number spectra of gravity wave motions in the stratosphere and mesosphere over the mid‐Pacific , 1994 .

[2]  D. Fried.  Optical Resolution Through a Randomly Inhomogeneous Medium for Very Long and Very Short Exposures , 1966 .

[3]  V. I. Tatarskii,et al.  Atmospheric turbulence and the resolution limits of large ground-based telescopes: comment , 1993 .

[4]  S. Corrsin.  On the Spectrum of Isotropic Temperature Fluctuations in an Isotropic Turbulence , 1951 .

[5]  A. S. Gurvich,et al.  Aspect Sensitivity of Radar Returns from Anisotropic Turbulent Irregularities , 1993 .

[6]  M. M. Colavita,et al.  Interferometric seeing measurements on Mt. Wilson: power spectra and outer scales. , 1995, Applied optics.

[7]  Francis Dalaudier,et al.  Middle stratosphere temperature spectra observed with stellar scintillation and in situ techniques , 1994 .

[8]  Francis Dalaudier,et al.  Direct comparison between in situ and radar measurements of temperature fluctuation spectra: A puzzling result , 1989 .

[9]  David L. Fried,et al.  Statistics of a Geometric Representation of Wavefront Distortion: Errata , 1965 .

[10]  M J Beran,et al.  Scintillation index calculations using an altitude-dependent structure constant. , 1988, Applied optics.

[11]  T. S. Mckechnie.  Atmospheric turbulence and the resolution limits of large ground-based telescopes: reply to comment by Tatarskii and Zavorotny. , 1993 .

[12]  E. Dewan.  Similitude modeling of internal gravity wave spectra , 1991 .

[13]  Steve Smith,et al.  Evidence for a Saturated Spectrum of Atmospheric Gravity Waves. , 1987 .