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Title: Effect of Background Emissivity on Gas Detection in Thermal Hyperspectral Imagery

Abstract

Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temper- ature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which describes at-sensor observed radiance. The background emissivity and plume/ground temperatures are isolated, and their effects on net chemical signal are described. This analysis shows that the plume’s physical state, emission or absorption, is directly dependent on the background emissivity. It then describes what conditions on the background emissivity have inhibiting effects on the net chemical signal. These claims are illustrated by analyzing synthetic hyperspectral imaging data with the Adaptive Matched Filter using four chemicals and three distinct background emissivities. Two chemicals (Carbontetrachloride and Tetraflourosilane) in the analysis had a very strong relationship with the background emissivities: they exhibited absorbance over a small range of wavenumbers and the background emissivities showed a consistent ordering at these wavenumbers. Analysis of simulated hyperspectral images containing these chemicals showed complete agreement with the analysis of the physics-based model that described when the background emissivities would have inhibiting effects on gas detection. The other chemicals considered (Ammonia and Tributylphosphate) exhibited very complexmore » absorbance structure across the longwave infrared spectrum. Analysis of images containing these chemicals revealed that the the analysis of the physics-based model did not hold completely for these complex chemicals but did suggest that gas detection was dominated by their dominant absorbance features. These results provide some explanation of the effect of the background emissivity on gas detection and a more general exploration of gas absorbance/background emissivity variability and their effects on gas detection is warranted. i« less

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
943410
Report Number(s):
PNNL-17874
NN2001000; TRN: US200902%%178
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; CARBON TETRACHLORIDE; SILANES; AMMONIA; TBP; DETECTION; EMISSIVITY; SIGNAL CONDITIONING; THERMAL ANALYSIS; GAS ANALYSIS

Citation Formats

Walsh, Stephen J., Tardiff, Mark F., Chilton, Lawrence K., and Metoyer, Candace N.. Effect of Background Emissivity on Gas Detection in Thermal Hyperspectral Imagery. United States: N. p., 2008. Web. doi:10.2172/943410.
Walsh, Stephen J., Tardiff, Mark F., Chilton, Lawrence K., & Metoyer, Candace N.. Effect of Background Emissivity on Gas Detection in Thermal Hyperspectral Imagery. United States. doi:10.2172/943410.
Walsh, Stephen J., Tardiff, Mark F., Chilton, Lawrence K., and Metoyer, Candace N.. Thu . "Effect of Background Emissivity on Gas Detection in Thermal Hyperspectral Imagery". United States. doi:10.2172/943410. https://www.osti.gov/servlets/purl/943410.
@article{osti_943410,
title = {Effect of Background Emissivity on Gas Detection in Thermal Hyperspectral Imagery},
author = {Walsh, Stephen J. and Tardiff, Mark F. and Chilton, Lawrence K. and Metoyer, Candace N.},
abstractNote = {Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temper- ature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which describes at-sensor observed radiance. The background emissivity and plume/ground temperatures are isolated, and their effects on net chemical signal are described. This analysis shows that the plume’s physical state, emission or absorption, is directly dependent on the background emissivity. It then describes what conditions on the background emissivity have inhibiting effects on the net chemical signal. These claims are illustrated by analyzing synthetic hyperspectral imaging data with the Adaptive Matched Filter using four chemicals and three distinct background emissivities. Two chemicals (Carbontetrachloride and Tetraflourosilane) in the analysis had a very strong relationship with the background emissivities: they exhibited absorbance over a small range of wavenumbers and the background emissivities showed a consistent ordering at these wavenumbers. Analysis of simulated hyperspectral images containing these chemicals showed complete agreement with the analysis of the physics-based model that described when the background emissivities would have inhibiting effects on gas detection. The other chemicals considered (Ammonia and Tributylphosphate) exhibited very complex absorbance structure across the longwave infrared spectrum. Analysis of images containing these chemicals revealed that the the analysis of the physics-based model did not hold completely for these complex chemicals but did suggest that gas detection was dominated by their dominant absorbance features. These results provide some explanation of the effect of the background emissivity on gas detection and a more general exploration of gas absorbance/background emissivity variability and their effects on gas detection is warranted. i},
doi = {10.2172/943410},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Oct 02 00:00:00 EDT 2008},
month = {Thu Oct 02 00:00:00 EDT 2008}
}

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