Physical Sciences Inc. has developed an ultra-compact shortwave infrared (SWIR) staring mode hyperspectral imaging (HSI) sensor with an additional visible full motion video (FMV) capability. The innovative HSI design implements a programmable micro-electromechanical system entrance slit that breaks the interdependence between vehicle speed, frame rate, and spatial resolution of conventional push-broom systems and enables staring-mode operation without cooperative motion of the host vehicle or aircraft. The FMV and HSI components fit within 1000 cm3, weigh a total of 2.1 lbs., and draw 15 W of power. The sensor mechanical design is compatible with gimbal-based deployment allowing for easy integration into ground vehicles or aircrafts. The FMV is capable of achieving NIRS-6 imagery over a 6°×6° field-of-view (FOV) at a 1500 ft. standoff. The SWIR HSI covers a spectral range of 900-1605 nm with a 15 nm spectral resolution, and interrogates a 5°×5° FOV per 1.6 s with a 2.18 mrad instantaneous FOV (1 m ground sample distance at 1500 ft.). A series of outdoor tests at standoffs up to 300 ft. have been conducted that demonstrate the payload’s capability to acquire HSI information. The payload has direct utility towards diverse remote sensing applications such as vegetation monitoring, geological mapping, surveillance, etc. The data product utility is demonstrated through the spectral identification of materials (e.g. foam and cloth) placed in the sensor’s FOV.
A compressive sensing hyperspectral imaging (CS-HSI) platform has been developed for low-cost, standoff, wide area Early Warning of chemical vapor plumes. The sensor, operating in the longwave infrared (LWIR) spectral range with a single-pixel architecture, simultaneously addresses two practical shortcomings of LWIR chemical plume imaging platforms: (1) the single pixel architecture enables an order of magnitude cost reduction relative to HSI sensors employing a cooled focal plane array or high-speed gimbaled scanner, and (2) the inherent imaging modality achieves a favorable pixel fill factor and associated probability of detection for relevant chemical threats relative to single pixel scanned sensors. The CS-HSI employs a low-cost digital micromirror device modified for use in the LWIR spectral range to spatially encode an image of the scene. An LWIR spectrometer employing a tunable Fabry-Perot filter and a mercury cadmium telluride single element photo-detector spectrally resolves the spatially integrated image while mitigating instrument radiance. A CS processing module reconstructs the spatially compressed hyperspectral image where the measurement and sparsity basis functions are specifically tailored to the CS-HSI hardware and chemical plume imaging. An automated target recognition algorithm is applied to the reconstructed hyperspectral data employing a variant of the Adaptive Cosine Estimator for the detection of the chemical plumes in cluttered and dynamic backgrounds. The development, characterization, and a series of capability demonstrations of a prototype CS-HSI sensor are presented. Capability demonstrations include chemical plume imaging of R-134 at mission-relevant concentration pathlength product levels in a laboratory setting.
KEYWORDS: Short wave infrared radiation, Vegetation, Sensors, Reflectivity, Digital micromirror devices, Signal to noise ratio, Spectral resolution, Data acquisition, Infrared imaging, Infrared radiation
A high-speed visible/near infrared, shortwave infrared (VNIR/SWIR) hyperspectral imaging (HSI) sensor for airborne, dynamic, spatially-resolved vegetation trait measurements in support of advanced terrestrial modeling is presented. The VNIR/SWIR-HSI sensor employs a digital micromirror device as an agile, programmable entrance slit into VNIR (0.5–1μm) and SWIR (1.2–2.4μm) grating spectrometer channels, each with a two-dimensional focal plane array. The sensor architecture, realized in a 13 lb package, is specifically tailored for deployment on a small rotary wing (hovering) unmanned aircraft system (UAS). The architecture breaks the interdependency between aircraft speed, frame rate, and spatial resolution characteristic of push-broom HSI systems. The approach enables imaging while hovering as well as flexible revisit and/or foveation over a region of interest without requiring cooperation by the UAS. Hyperspectral data cubes are acquired on the second timescale which alleviates the position accuracy requirements on the UAS’s GPS-IMU. The sensor employs a simultaneous and boresighted visible context imager for pan sharpening and orthorectification. The data product is a 384×290 (spatial) ×340 (spectral) format calibrated, orthorectified spectral reflectivity data cube with a 26×20° field of view. The development, characterization, and a series of capability demonstrations of an advanced prototype VNIR/SWIR HSI sensor are presented. Capability demonstrations include ground-based testing as well as flight testing from a commercial rotary wing UAS with remote operation of the HSI sensor via a dedicated ground station.
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