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Proceedings Paper

Terahertz target illumination fluctuation estimates derived from field measurements of atmospheric water vapor
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Paper Abstract

Many terahertz imaging systems under development will be employed in outdoor environments, where spatial and temporal fluctuations of atmospheric absorbing species can affect image quality. Absorption across most of the terahertz band is dominated by water vapor. Active systems that illuminate targets with scanned ("flying spot") or floodlight terahertz sources will experience some spatial and temporal noise modulation of target plane irradiance due to path-integrated inhomogeneities in the turbulent water vapor density field. We have analyzed data collected during field measurement campaigns conducted at the White Sands Missile Range during the spring and summer of 2007 for spectral characteristics and diurnal variations of water vapor fluctuations under dry to moderately humid synoptic conditions. The results of these analyses were then used to model the statistics of irradiance fluctuations that might be observed in the target plane of a THz imager under varying propagation conditions. The measurements acquired can also be compared with a statistical model of path-integrated absorptance considering either the evolution of the absorption with time or the effects of decorrelation in absorber for two angularly separated lines-of-sight.

Paper Details

Date Published: 15 April 2008
PDF: 11 pages
Proc. SPIE 6949, Terahertz for Military and Security Applications VI, 694906 (15 April 2008); doi: 10.1117/12.783073
Show Author Affiliations
Sean G. O'Brien, U.S. Army Research Lab. (United States)
David H. Tofsted, U.S. Army Research Lab. (United States)

Published in SPIE Proceedings Vol. 6949:
Terahertz for Military and Security Applications VI
James O. Jensen; Hong-Liang Cui; Dwight L. Woolard; R. Jennifer Hwu, Editor(s)

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