Showing papers by "Norman S. Kopeika published in 1988"

Optical, infrared, and millimeter wave propagation engineering

Abstract: These proceedings collect papers on wave propagation. Topics include: statistics of propagation, atmospheric effects, scattering of laser beams by media, high energy laser-assisted imaging through vaporizing aerosols, optical turbulence, and turbulent wavefront sensing and image processing.

Prediction of effects of weather on image quality: preliminary results of model validation.

Abstract: Using the atmospheric modulation transfer function area (MTFA) as a single-valued numerical criterion for image quality horizontally near the ground propagated through the atmosphere, a statistical study of atmospheric imaging data accumulated over a three-year period has led to the determination of regression coefficients with which to quantitatively predict image quality as a function of wavelength, over the 400-1000- nm wavelength region, according to weather forecast. Utilization of this procedure is simple: one plugs in expected values for wind speed, air temperature, and relative humidity in the regression coefficient expression for MTFA. The larger the expected MTFA, the better the expected image quality. Two sets of regression coefficient data have been obtained, one each for desert and nondesert climates, corresponding to summer and winter data here. Preliminary experimentation over a different line of sight indicates that the accuracy of the prediction is fairly reliable.

Overview Of Imaging Through The Atmosphere

Abstract: Turbulence, atmospheric background, and aerosol forward scattering modulation transfer functions 0M Fs) are analyzed. For diagonal or vertical imaging turbulence is seen to limit image quality only at very high spatial frequencies, where degradation is likely to take place anyway as a result of vibration and diffraction. Background and aerosol MTFs limit law spatial frequency contrast as well. For long-range horizontal lines-of-sight near ground level, both turbulence and forward scattering by aerosols severely limit image quality. Numerical examples are presented. These limitations can be overcome somewhat by proper selection of the imaging wavelength and of operation timing. This analysis can aid in sensor selection for system design from the standpoints of both wavelength selection and sensor resolution. Because this analysis includes the effects of weather changes on image propagation through the atmosphere, and a model for predicting image quality as a function of weather forecast, it also can aid in selecting operation timing on the basis of weather forecasts, with a view toward optimizing expected resolution.

Prediction Of Effects Of Weather On Image Quality Propagated Through The Atmosphere

Abstract: Using atmospheric modulation transfer function area (MTFA) as a single-valued numerical criterion for image quality propagated through the atmosphere horizontally near the ground, a statistical study of atmospheric imaging data accumulated over a three year period has led to the determination of regression ceofficients with which to quantitatively predict image quality as a function of wavelength, over the 400 - 1000 nm wavelength region, according to weather forecast. Utilization of this procedure is quite simple. One simply plugs in expected values for windspeed, air temperature, and relative humidity in the regression coefficient expression for MTFA. The larger the expected MTFA, the better the expected image quality. Two sets of regression coefficient data have been obtained, one each for desert and non-desert climates, corresponding to summer and winter data here. Preliminary experimentation over a different line-of-sight indicates the accuracy of the prediction is fairly reliable for the summer or desert model.