Accession Number : ADA119575

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

Descriptive Note : Technical rept.,


Personal Author(s) : Replogle,Frank S , Jr

PDF Url : ADA119575

Report Date : 13 Jul 1982

Pagination or Media Count : 46

Abstract : This report presents a mechanism to calculate the optical index structure constant, C2N 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 are calculated. Finally, three series of photographic line-width observations (made during unstable, neutral, and stable atmospheric buoyancy conditions) are compared with calculated line widths. Mean values of observed results agree with the calculations within about 25 percent 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 percent for conditions of strong atmospheric instability. Observations made under conditions of neutral and stable atmospheric buoyancy were instrumentally limited to an angular sub-tense of 2 to 4 arc-sec. 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 is indicative of the difficulty of employing a single mechanism to correct for atmospherically induced image-smear. (Author)

Descriptors :   *Optical images, *Meteorological phenomena, Line of sight, Ocean surface, Quality, Computations, Meteorological data, Turbulence, Light transmission, Visual targets, Lines(Geometry), Black and white photography, Width, Measurement, Cross correlation, Marine meteorology

Subject Categories : Photography

Distribution Statement : APPROVED FOR PUBLIC RELEASE