Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XVI, 2010
ABSTRACT Remote sensing by infrared spectroscopy allows identification and quantification of atmo... more ABSTRACT Remote sensing by infrared spectroscopy allows identification and quantification of atmospheric gases as well as airborne pollutants. An application of the method that has gained increased interest in recent years is remote sensing of hazardous gases. If hazardous compounds are released into the atmosphere, for example in the case of a chemical accident, emergency response forces require information about the released compounds immediately in order to take appropriate measures to protect workers, residents, and the environment. A hyperspectral sensor allows identification and visualisation of hazardous clouds in the atmosphere from long distances. The image of a cloud allows an assessment of the dimensions and the dispersion of a cloud. In addition, the source of a cloud may be located. A hyperspectral sensor based on an imaging Fourier-transform spectrometer with a focal plane array detector is currently being developed for this application. Compared to conventional spectrometers, hyperspectral systems allow the use of spatial information in addition to spectral information. In addition to the application of remote sensing of hazardous gases, the system may be applied in other fields of research such as the detection of liquids and atmospheric measurements. In this work, the HYGAS system and first results of measurements are presented.
Remote Sensing of Clouds and the Atmosphere X, 2005
ABSTRACT The method of passive remote sensing by Fourier transform spectroscopy allows the retrie... more ABSTRACT The method of passive remote sensing by Fourier transform spectroscopy allows the retrieval of column densities or concentrations of molecules in gas plumes such as exhaust gas plumes of aircraft or vapor plumes emitted after chemical accidents. State- of-the-art retrieval algorithms require two models: a radiative transfer model and an instrument model, the instrument line shape (ILS). The instrument line shape of real Fourier transform spectrometers (FTS) differs significantly from the instrument line shape of an ideal FTS, in particular if the instrument is optimized for high signal-to-noise ratio, which is achieved by interferometer designs with high optical throughput (etendue). The real instrument line shape may be modeled by convolution of the instrument line shape of the ideal FTS with an inherent instrument line shape describing the deviations. In this work, the inherent instrument line shape is modeled by a function which is dependent on a small number of parameters. In order to determine these parameters automatically, a new method has been developed. Spectra of a well-known gas in a gas cell are measured. The measured spectrum is approximated using a least squares fit with a model that contains the parameters of the instrument line shape. The fitting procedure is performed automatically. The instrument line shape model, the experimental setup of the method for the determination of the instrument line shape, and results of measurements using the instrument line shape are presented. In addition to the analysis of spectra with the ILS determined by the new method, analysis results obtained with an ideal instrument line shape are presented to demonstrate the negative effect of an inaccurate instrument line shape on the retrieved column density.
Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XVI, 2010
ABSTRACT Remote sensing by infrared spectroscopy allows identification and quantification of atmo... more ABSTRACT Remote sensing by infrared spectroscopy allows identification and quantification of atmospheric gases as well as airborne pollutants. An application of the method that has gained increased interest in recent years is remote sensing of hazardous gases. If hazardous compounds are released into the atmosphere, for example in the case of a chemical accident, emergency response forces require information about the released compounds immediately in order to take appropriate measures to protect workers, residents, and the environment. A hyperspectral sensor allows identification and visualisation of hazardous clouds in the atmosphere from long distances. The image of a cloud allows an assessment of the dimensions and the dispersion of a cloud. In addition, the source of a cloud may be located. A hyperspectral sensor based on an imaging Fourier-transform spectrometer with a focal plane array detector is currently being developed for this application. Compared to conventional spectrometers, hyperspectral systems allow the use of spatial information in addition to spectral information. In addition to the application of remote sensing of hazardous gases, the system may be applied in other fields of research such as the detection of liquids and atmospheric measurements. In this work, the HYGAS system and first results of measurements are presented.
Remote Sensing of Clouds and the Atmosphere X, 2005
ABSTRACT The method of passive remote sensing by Fourier transform spectroscopy allows the retrie... more ABSTRACT The method of passive remote sensing by Fourier transform spectroscopy allows the retrieval of column densities or concentrations of molecules in gas plumes such as exhaust gas plumes of aircraft or vapor plumes emitted after chemical accidents. State- of-the-art retrieval algorithms require two models: a radiative transfer model and an instrument model, the instrument line shape (ILS). The instrument line shape of real Fourier transform spectrometers (FTS) differs significantly from the instrument line shape of an ideal FTS, in particular if the instrument is optimized for high signal-to-noise ratio, which is achieved by interferometer designs with high optical throughput (etendue). The real instrument line shape may be modeled by convolution of the instrument line shape of the ideal FTS with an inherent instrument line shape describing the deviations. In this work, the inherent instrument line shape is modeled by a function which is dependent on a small number of parameters. In order to determine these parameters automatically, a new method has been developed. Spectra of a well-known gas in a gas cell are measured. The measured spectrum is approximated using a least squares fit with a model that contains the parameters of the instrument line shape. The fitting procedure is performed automatically. The instrument line shape model, the experimental setup of the method for the determination of the instrument line shape, and results of measurements using the instrument line shape are presented. In addition to the analysis of spectra with the ILS determined by the new method, analysis results obtained with an ideal instrument line shape are presented to demonstrate the negative effect of an inaccurate instrument line shape on the retrieved column density.
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