Passive infrared hyperspectral imaging for standoff detection of tetryl explosive residue on a steel surface

A commercial imaging FTIR spectrometer that operates between 850 and 1300 cm^-1 was used to passively image a galvanized steel plate stained with a residue of the explosive tetryl (2, 4, 6, N-tetranitro-N-methylaniline). The tetryl was coated onto the plate in a 30 cm diameter spot with an areal dosage of 110 μg tetryl/cm². The stain on the plate was easily detected at standoff distances of 14 and 31 m by examining the hyperspectral data cubes using maximum autocorrelation factors and a slight modification to a generalized least squares target detection algorithm. End-member extraction showed good comparison in a few key bands between the target end-member and laboratory reflectance spectra; however, significant differences were also observed.