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Proceedings Paper

Synthetic IR Cloud Image Model
Author(s): J. Conant; D. Dvore; J. Gruninger
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Paper Abstract

The presence of clouds affects most infrared (IR) military sensors. Foreground clouds degrade or occult target signatures and background clouds clutter a scene. Models used to assess or predict system performance must include important features of clouds: absorption, single and multiple scattering, thermal emission, partial transmission and spatial non-uniformity. Exact models which account for the details of cloud microphysics require large computation times and inputs which are difficult to obtain. Aerodyne has developed an approximate model which produces realistic cloud scenes in a reasonable amount of computer time. An average optical depth for the cloud is first calculated by use of LOWTRAN6 with specified aerosol optical properties. These properties are combined with a multiple scattering model which uses a two stream approximation. This model assumes that 1) the cloud layer is a parallel plane and infinite, 2) there is a constant single scattering albedo which may be wavelength dependent, 3) there is local thermodynamic equilibrium between particles and atmospheric gases, and 4) there is a uniform cloud temperature and emissivity. The result is an average cloud radiance spectrum along a specified line-of-sight. The line-of-sight may be up-looking or down-looking, and up to two cloud layers may be present. Spatial non-uniformities are incorporated by use of a cloud texture model based on a 1/f spectral shaping of spatial variations. The final scene including the effect of the atmospheric path from the cloud to the observer is in-band integrated and recorded as a grid of radiances with an associated depth map for use in a target/background interface model.

Paper Details

Date Published: 24 August 1988
PDF: 11 pages
Proc. SPIE 0933, Multispectral Image Processing and Enhancement, (24 August 1988); doi: 10.1117/12.968475
Show Author Affiliations
J. Conant, Aerodyne Research, Inc. (United States)
D. Dvore, Aerodyne Research, Inc. (United States)
J. Gruninger, Aerodyne Research, Inc. (United States)

Published in SPIE Proceedings Vol. 0933:
Multispectral Image Processing and Enhancement
Marshall R. Weathersby, Editor(s)

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