Remote Measurement of Highly Toxic Vapours by Scanning Imaging Fourier-Transform Spectrometry

In the case of chemical accidents, terrorist attacks, or war, hazardous compounds may be released into the atmosphere. Remote sensing by Fourier-transform infrared spectrometry allows identification and quantification of these hazardous clouds. The output of current standoff detection systems is a yes/no decision by an automatic identification algorithm that analyses the measured spectrum. The interpretation of the measured spectrum by the operator is complicated and thus this task requires an expert. Even if a scanning system is used for surveillance of a large area the operator is dependent on the decision of the algorithm. In contrast to that, imaging systems allow automatic identification but also simple interpretation of the result, the image of the cloud. Therefore, an imaging spectrometer, the scanning infrared gas imaging system (SIGIS) has been developed. The system is based on an interferometer with a single detector element (Bruker OPAG 22) in combination with a telescope and a synchronised scanning mirror. The results of the analyses of the spectra are displayed by an overlay of a false colour image, the “chemical cloud image”, on a video image. In this work, the first application of the system as chemical warfare agent identification and imaging system is described. The system, the data analysis method, and results of measurements of chemical warfare agents are presented.