Identification and Detection of Bacterial Spores With a Passive FTIR in an Open Air Point Release

A simple experiment was conducted in order to test the feasibility of a high-sensitivity Fourier transform infrared (FTIR) spectrometer a passive infrared spectrometer to measure open air point release of dry Bacillus subtilis var. niger (BG) spores. The release was partially contained in order to provide a stable cloud. Measurements were taken continuously through a horizontal line of sight with a complex background (sky and mountains at a distance of a few tens of kilometers) at a distance of 50 meters. The temperature difference (background to ambient air) was a few degrees Kelvin. Advanced identification and detection algorithms, based on radiative transfer theory and statistical signal processing methods were developed and used during the experiment. The deduced absorption spectra (Identification) show an excellent match to a BG absorption spectrum and thus indicate that the released material was BG. Analysis of the time sequence of the measurements via an adaptive detection threshold coincides very well (Detection) with the presence of the BG during the measurements. For completion we also show measurements of Kaolin dust where the ability to distinguish between the spectrum of BG and Kaolin is shown. Our experiment and analysis clearly show the feasibility of passive remote sensors to detect and identify BG particles. These results are encouraging and more experiments to validate our models and to explore their limitations are planned. See also ADM001523., The original document contains color images.