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

Sean G. O'Brien; David H. Tofsted

doi:10.1117/12.783073

15 April 2008 Terahertz target illumination fluctuation estimates derived from field measurements of atmospheric water vapor

Sean G. O'Brien, David H. Tofsted

Author Affiliations +

Proceedings Volume 6949, Terahertz for Military and Security Applications VI; 694906 (2008) https://doi.org/10.1117/12.783073
Event: SPIE Defense and Security Symposium, 2008, Orlando, Florida, United States

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.

Citation Download Citation

Sean G. O'Brien and David H. Tofsted "Terahertz target illumination fluctuation estimates derived from field measurements of atmospheric water vapor", Proc. SPIE 6949, Terahertz for Military and Security Applications VI, 694906 (15 April 2008); https://doi.org/10.1117/12.783073

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