The AHI (Airborne Hyperspectral Imager) system was designed to detect the presence of buried land mines from the air through detection of along wave IR observable associated with mine installation. The system is a helicopter-borne LWIR hyperspectral imager with real time on-board radiometric calibration and mine detection. It collects hyperspectral imagery from 7.5 to 11.5 μm in either 256 or 32 spectral bands. At all wavelengths the AHI noise equivalent delta (NEΔT) temperature is less than 0.1K at 300K and the NESR is less than .02 watts/m2-sr-μm.
Under the sponsorship of the DARPA Hyperspectral Mine Detection program, a series of both non-imaging and imaging experiments have been conducted to explore the physical basis of buried object detection in the visible through thermal infrared. Initially, non-imaging experiments were performed at several geographic locations. Potential spectral observables for detection of buried mines in the thermal portion of the infrared were found through these measurements. Following these measurements with point spectrometers, a series of hyperspectral imaging measurements was conducted during the summer of 1995 using the SMIFTS instrument from the University of Hawaii and the LIFTIRS instrument from Lawrence Livermore National Laboratory. The SMIFTS instrument (spatially modulated imaging Fourier transform spectrometer) acquires hyperspectral image cubes in the short-wave and mid-wave infrared and LIFTIRS (Livermore imaging Fourier transform infrared spectrometer) acquires hyperspectral image cubes in the long-wave infrared. Both instruments were optimized through calibration to maximize their signal to noise ratio and remove residual sensor pattern. The experiments were designed to both explore further the physics of disturbed soil detection in the infrared and acquire image data to support the development of detection algorithms. These experiments were supported by extensive ground truth, physical sampling and laboratory analysis. Promising detection observables have been found in the long-wave infrared portion of the spectrum. These spectral signatures have been seen in all geographical locations and are supported by geological theory. Data taken by the hyperspectral imaging sensors have been directly input to detection algorithms to demonstrate mine detection techniques. In this paper, both the non-imaging and imaging measurements made to date will be summarized.
The use of hyperspectral visible and infrared sensors is being explored under an ARPA program to provide a means for the detection of buried mines. The purpose of this paper is to summarize the status of the phenomenology of the detection of buried mines using hyperspectral IR detection mechanisms. Both spectral and temperature phenomena related to buried mines will be investigated in the paper. Concepts using the midwave IR (3 to 5 micrometers ), the longwave IR (8 to 12 micrometers ) and the reflection IR (from 1.1 to 2.5 micrometers ) are emphasized in this current effort, although the full IR and visible spectra is considered. Thermally dominated IR is emphasized because of the desire for day/night operation. The program is initially focusing on nonimaging spectrometer measurements of top layers of soil and subsoil, to determine the presence of spectral differences that can be an indicator of mine placement. These spectrometer measurements will be followed by measurements with hyperspectral imaging sensors. While many broad measurements have been made in the MWIR and LWIR, few measurements have been made with an imaging spectrometer. The ARPA/University of Hawaii Spatially Modulated Imaging Fourier Tranform Spectrometer (SMIFTS) can provide such data in the 1.1 to 5.0 micrometers band and the Lawrence Livermore National Laboratory's Livermore Imaging Fourier Transform Infrared Spectrometer (LIFTIRS) will cover the 8-12 micrometers region. The sensors will be deployed in the field from an elevated platform to acquire data in support of both the phenomenology verification and the development of algorithms.