Accession Number : ADA113894

Title :   Prediction of Optical Image Quality Near the Sea Surface from Meteorological Measurements.

Descriptive Note : Technical memo.,


Personal Author(s) : Replogle,F S , Jr ; Fairall,C W

PDF Url : ADA113894

Report Date : 25 Jan 1982

Pagination or Media Count : 54

Abstract : This report presents a mechanism for calculation of the optical index structure constant from bulk meteorological measurements (air and water temperatures, wind speed, air humidity) made over the ocean. From this and a formulation of the near field optical propagation from an incoherent point source, the expected line spread function for near the sea surface lines of sight is calculated. Finally, three series of photographic line width observations, made during unstable, neutral, and stable atmospheric buoyancy conditions, are compared with line widths expected from the calculations. Mean values of observed results agree with the calculations within about 25% for conditions of strong atmospheric instability. Since comparisons were made over a variety of target ranges, wind speeds, and camera elevations, it is concluded that the formulations derived are accurate to at least + or - 25% for conditions of strong atmospheric instability. The observations made under conditions of neutral and stable atmospheric buoyancy were instrumentally limited to an angular subtense of 2 to 4 arc seconds. These measured line width values fall between 1.9 and 0.6 times the values computed from meteorological measurements. The variability of image spreading observed across the target fields points out the difficulty of employing a single mechanism for correction of atmospherically induced image smear. (Author)

Descriptors :   *Photographic images, *Light transmission, Refractive index, Atmospheric refraction, Ocean surface, Surface temperature, Atmospheric motion, Turbulence, Humidity, Atmospheric temperature, Incoherent scattering, Neutral, Buoyancy, Air water interactions, Cameras, Elevation, Line of sight, Meteorological data, Mathematical models, Constants, Indexes(Ratios), Photographic recording systems, Quality

Subject Categories : Meteorology

Distribution Statement : APPROVED FOR PUBLIC RELEASE