Remote Measurement of Emissions by Scanning Imaging Infrared

Remote sensing by Fourier-transform infrared spectrometry allows identification and quantification of emissions from long distances. Imaging spectrometry allows to characterise emissions spatially as well as automated surveillance of large and potentially inaccessible areas. In this work, scanning imaging remote sensing spectrometers (SIGIS and SIGIS 2) have been deployed to identify and visualise industrial emissions. The systems are based on Michelson interferometers with a single detector element in combination with telescopes and synchronised scanning mirrors. For simple interpretation of the results, the systems are equipped with video cameras and the results of the analyses of the spectra are displayed by an overlay of a false colour image on the video image. This allows a simple evaluation of the position and the size of an exhaust plume. The analysis method is based on the evaluation of the radiance spectrum and the brightness temperature spectrum. In order to perform the radiometric calibration that is required to calculate the radiance spectrum, the spectrometers are equipped with automated calibration systems. The analysis is performed by modelling the measured spectrum using reference spectra of the target compounds as well as reference spectra of atmospheric species. In order to obtain high signal-to-noise ratios and short measurement times, measurements are performed with a relatively low spectral resolution. The low-resolution spectra (spectral resolution of the measurement) are modelled using high-resolution reference spectra in combination with an instrument line shape model that is defined by five parameters. Measurements of emissions were performed at various industrial sites.