Remote sensing of gases by hyperspectral imaging: system performance and measurements

Remote gas detection and visualization provides vital information in scenarios involving gas leaks, environmental monitoring, chemical accidents or attacks. Imaging systems based on Fourier transform spectrometers with single detector elements have been applied for several years by emergency response forces for gas identification and quantification. In this work a hyperspectral imager employing a Michelson interferometer and an infrared focal plane array detector is characterized. The system provides spatially resolved spectral information about the measurement scene. The performance of the system is evaluated by laboratory measurements. Results of gas detection in the field are presented and discussed. The gas detection algorithm is based on a physical model for the measured radiance. In this model the atmosphere is divided into multiple homogenous layers of constant temperature. The signatures of the gases present in these layers are then compensated in the measured spectrum. No information about the signature of the background is required. Moreover an algorithm that combines spectral and spatial information is presented. This algorithm enhances the signal to noise ratio of the spectra and thus improves the detection limits. Using these algorithms it is possible to identify, visualize, and track gas clouds in real time.