Current Ground-based Lwir His Remote Sensing Activities at Defense R&d Canada - Valcartier

Recently, DRDC Valcartier has been investigating novel ground-based longwave hyperspectral imaging (HSI) remote sensing techniques. Specific projects include the development of a new ground-based sensor called MoDDIFS (Multi-Option Differential Detection and Imaging Fourier Spectrometer), which is a leading edge infrared (IR) hyperspectral imaging (HSI) sensor optimized for the standoff detection of explosive vapours and precursors. The development of the MoDDIFS sensor is based on the integration of two innovative technologies: (1) the differential Fourier-transform infrared (FTIR) radiometry technology found in the Compact Atmospheric Sounding Interferometer (CATSI) previously developed by DRDC Valcartier, and (2) the HSI technology developed by Telops. The MoDDIFS sensor will offer the optical subtraction capability of the CATSI system but at high-spatial resolution using an MCT focal plane array of 84×84 pixels. The MoDDIFS sensor offers the potential of simultaneously measuring differential linear polarizations to further reduce the clutter in the measured radiance. 1. PASSIVE STANDOFF DIFFERENTIAL DETECTION AND CATSI The CATSI sensor [1,2] is a passive infrared system designed for the standoff detection of chemical vapours. Its differential detection capability provides two unique features for a field-deployable instrument. First, CATSI, as shown in Fig. 1A, maintains a constant calibration, thereby providing reliable quantitative measurements over a long period of time. Secondly, it can perform the real-time optical subtraction of the background signal from the target signal without the need for extensive calculations. Supported by unique acquisition software (GASEM) [3], CATSI is capable of on-line chemical vapour identification based on the spectral emission signatures of gases measured in the infrared region from 7 to 14 μm. Current methods for the passive standoff detection of chemical vapours by FTIR spectrometry are often limited by the large clutter IR emission from the intervening atmosphere and background. In order to mitigate the clutter impact and reduce the processing burden, the differential detection approach offered by CATSI measures the IR radiation from a target scene which is optically combined onto a single detector outof-phase with the IR radiation from a corresponding background scene, resulting in the target signature being detected in real-time void of significant background clutter. During the past ten years, the sensitivity and accuracy of the differential detection approach with the CATSI sensor has been well established at several field trials. This work includes a major U.S. open-air field trial in Nevada (2001), and a trial at DRDC Valcartier for a standoff distance of 5.7 km (Fig. 1B,C) [4,5]. Experiments such as these have clearly demonstrated the outstanding capability of the technique (CATSI and GASEM) for on-line monitoring and surveillance. 2. MoDDIFS SENSOR PROJECT The success of the CATSI system for detecting chemical vapours has led to the development of a novel R&D prototype, MoDDIFS, to address the standoff detection of explosives and precursors [6]. The MoDDIFS system provides a differential imaging capability that may be useful for the passive standoff detection of vapours from particular explosives and precursors. This can provide early detection and warning of a belligerent’s intent and their level of readiness to mount an attack with improvised explosives. The sensor is optimized for explosives and precursor detection based on phenomenological and modeling studies and a new library of relevant explosive and precursor signatures. MoDDIFS is a project sponsored by the Canadian CBRNE Research and Technology Initiative (CRTI) program.