A thermal infrared hyperspectral imager (tasi) for buried landmine detection

Abstract

DRDC Suffeld and Itres Research have collaborated to investigate the use of hyperspectral imaging (HSI) for surface and buried landmine detection since 1989. Visible/near infrared (<i>casi</i>) and short wave infrared (<i>sasi</i>) families of imagers have been developed which have demonstrated reliable HSI detection of surface-laid mines, based on their reflectance spectra, from airborne and ground-based platforms. However, they have limited ability to detect buried mines. Thermal infrared (TIR) HSI may have the capability to detect buried mines. Disturbance of quartz-bearing soils has been shown to measurably change their TIR emissivity spectra due to mixing of surface/subsurface soil (restrahlen band intensities vary with particle size). Some evidence suggests that the effect can persist months after the visible disturbance has disappeared. Carbonates and other materials exhibit similar TIR spectral features and heat flow anomalies caused by buried mines can also be measured in the TIR band. There are no commercially available TIR hyperspectral imagers that are suitable for mine detection. The very few possibly suitable imagers are one-of-a-kind research instruments, dedicated to internal programs and not available for the general mine detection community. A TIR hyperspectral imager (<i>tasi</i>) based on a novel optical design and a cooled MCT focal plane array has been developed. The instrument has been designed with landmine detection in mind. First light images from the prototype were obtained in summer 2006 and initial test flights were completed in fall 2006. The design of the instrument and a comparison with design alternatives in the context of mine detection requirements is discussed. Preliminary images are presented.