25 October 2006 Remote detection of chemicals with passive millimeter waves
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Passive millimeter-wave (mmW) systems have been used in the past to remotely map solid targets and to measure low-pressure spectral lines of stratospheric and interstellar gases; however, its application to pressure-broadened spectral detection of terrestrial gases is new. A radiative transfer model was developed to determine the detection feasibility and system requirements for passive mmW spectral detection. A Dicke-switched multispectral radiometer that operates at 146-154 GHz was designed and built for remote detection of stack gases. The radiometer was tested in the laboratory using a gas cell; the spectra of acetonitrile were detected passively against a cold background, which mimicked typical remote detection scenarios in the field. With Dicke-switched integration of radiometric signals, on-line calibration, and novel signal processing to minimize atmospheric fluctuation, spectral line detection of polar molecules is possible from chemical plumes a few kilometers away.
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N. Gopalsami, N. Gopalsami, S. Bakhtiari, S. Bakhtiari, T. W. Elmer, T. W. Elmer, A. C. Raptis, A. C. Raptis, } "Remote detection of chemicals with passive millimeter waves", Proc. SPIE 6378, Chemical and Biological Sensors for Industrial and Environmental Monitoring II, 63781A (25 October 2006); doi: 10.1117/12.690212; https://doi.org/10.1117/12.690212

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