Accession Number : ADA316593

Title :   Atmospheric Ray Tracing for Predicting Mirages.

Descriptive Note : Final rept. Nov 94-May 95,

Corporate Author : INSTITUTE FOR DEFENSE ANALYSES ALEXANDRIA VA

Personal Author(s) : Kay, Irvin W.

PDF Url : ADA316593

Report Date : MAY 1995

Pagination or Media Count : 39

Abstract : At infrared-optical frequencies the Edlen formula determines the index of refraction profile in a continuous, spherically symmetric atmosphere in terms of the pressure and temperature. Since the pressure dependence is known in terms of the temperature when equilibrium exists, a given temperature profile determines that of the index of refraction. The classical equation for rays propagating in such a medium then provides various geometrical properties of a ray, given its nearest minimum or maximum height relative to a specified viewing eye through which it passes. For altitudes above the surface of the Earth that are small compared to its radius the propagation geometry can be approximated in terms of a plane stratified medium above a flat ground surface. However, for distances large enough to include a horizon ray, a single corresponding approximate index of refraction profile is only valid for predicting the behavior of nearby rays. The slope of the index of refraction profile as well as that of the temperature determine the sign of the curvature of any ray at any height. Using the relationship between geometrical properties of the index of refraction profile it is possible to draw qualitative conclusions about the nature of possible mirages.

Descriptors :   *REFRACTIVE INDEX, *ATMOSPHERIC REFRACTION, IMAGE PROCESSING, ATMOSPHERIC TEMPERATURE, TEMPERATURE GRADIENTS, INFRARED IMAGES, EARTH SURFACE, BAROMETRIC PRESSURE, RAY TRACING, STRATIFICATION, INFRARED SPECTRA, INFRARED OPTICAL SYSTEMS.

Subject Categories : Optics
      Meteorology

Distribution Statement : APPROVED FOR PUBLIC RELEASE