Accession Number : AD0850030

Title :   The Effect of Atmospheric Scattering on Optical Beam Intensity at Low Visibility,

Corporate Author : FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OH

Personal Author(s) : Miler, M. ; Chomat, M.

Report Date : 21 NOV 1968

Pagination or Media Count : 12

Abstract : Atmospheric attenuation of an optical beam caused by scattering in fog was measured using an incoherent GaAs diode emitter in the 900-nm infrared band. The beam was concentrated to about 10 angular minutes by a 1-kHz moderator. The receiving photomultiplier and interference filter were placed at a distance of 600 m (through thick fog) across an artificial lake. Three forms of light scattering are described and a formula is presented for visibility based on the attenuation coefficient and wavelength for Rayleigh scattering. A formula for attenuation is given, and other experimental findings, such as the effect of size of moisture droplets, of nonhomogeneous waves of thick fog, and of homogeneous fog cover, are given. In homogeneous fog, minimum visibility was 300 m and the maximum attenuation 20 db/km; in extremely dense fog visibility was 50 m and attenuation 180 db/km, which indicates why optical navigation signals are not reliable under such conditions. (Author)

Descriptors :   (*ATMOSPHERES, LIGHT TRANSMISSION), (*FOG, SCATTERING), ATTENUATION, VISIBILITY, RAYLEIGH SCATTERING, GALLIUM ARSENIDES, INFRARED RADIATION, MOISTURE, DROPS, NAVIGATION, OPTICAL PROPERTIES, EMISSIVITY, SOURCES, MATHEMATICAL ANALYSIS, CZECHOSLOVAKIA.

Subject Categories : Atmospheric Physics
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE