Meteorological Effects On Image Quality: Reconnaissance Considerations

Abstract

Calculations are made of regression coefficients for relative humidity, air temperature, and windspeed, with respect to atmospheric contrasts in various wavelength bands over visible and near IR wavelengths as measured over a 3 year period. Significant changes are noted between summer and winter, including some sign changes and opposing wavelength dependences. Analysis of spatial frequency data indicates in the rainy season, when the atmosphere is freer of airborne soil-derived particulates, turbulence is dominant in limiting imaging resolution through the atmosphere, with wavelength dependence determined primarily by background and forward scattering effects associated with humidity. Resolution is best in the near infrared. However, in the dry season image quality is limited primarily by large airborne particulates and their effects on atmospheric background and spatial frequency-dependent multiple forward scattering phenomena. As a result, resolution is best at short wavelengths. The strong wavelength dependences on small and large radii aerosol related effects suggest the possibility of predicting imaging resolution spectral dependence in advance in accordance with meteorological predictions. Analysis of regression coefficients in the spatial frequency domain permits quantitative determination of effects of each meteorological parameter on each type of atmospheric MTF, i.e., background, aerosol, and turbulence MTF's separately. In this way insight is gained as to not only the extent to which each meteorological parameter effects imaging resolution, but also the mechanism of the effect.