Imaging Remote Sensing Fourier Transform Spectrometer with a Focal Plane Array Detector: First Measurements

Passive remote sensing by infrared spectrometry allows detection and identification of hazardous clouds from long distances. Typical applications of the method are automatic surveillance of industrial facilities and identification of hazardous clouds after chemical accidents. A conventional remote sensing Fourier transform infrared spectrometer is based on an interferometer with a single detector element. The output of the system is usually a yes/no decision by an automatic identification algorithm that analyses the measured spectrum. The analysis 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. An imaging spectrometer with these capabilities is the scanning infrared gas imaging system (SIGIS). The system is based on an interferometer with a single detector element in combination with a telescope and a synchronized scanning mirror. The results of the analyses of the spectra are displayed by an overlay of a false color image, the “hazardous chemical image”, on a video image. However, the temporal resolution of the system is limited by the sequential measurement of all fields of view within the field of regard. In order to measure a complete image by a single scan of the interferometer, an imaging Fourier-transform spectrometer (IFTS) with a detector array instead of a single detector element is currently being developed at TUHH. In this work, the first measurements are presented.