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Compact Broadband Thermal Imaging and LWIR HSI Payload for Small Unmanned Aircraft System (SUAS)

Description:

TECHNOLOGY AREA(S): Sensors 

OBJECTIVE: Develop compact payload capable of collecting high spatial resolution thermal imagery and wide area longwave infrared (LWIR) hyperspectral imagery (HSI) to fit within the constraints of a 5" gimbal for use with SUAS platforms. 

DESCRIPTION: The Air Force has a need to perform ISR in contested environments. Group I and II SUAS (i.e., those under 55 lbs) are potential enablers for such missions due to their low cost and low probability of detection. However, they lack sensors for nighttime, automated passive detection/ID over large areas, particularly for difficult targets like those hidden by camouflage, concealment, or deception. ISR using longwave infrared (LWIR) hyperspectral imaging (HSI) systems has demonstrated utility in those challenging scenarios, but existing systems are too large and do not meet the size, weight, power (SWaP) constraints imposed by SUAS. This topic seeks development of uncooled LWIR HSI systems or development of novel compact cooled systems to be integrated with a broadband thermal imaging system (either MWIR or LWIR) to fit within the SWaP constraints of a 5” gimbal and corresponding SUAS. This effort will provide a 5” diameter gimbal suitable for a Common Launch Tube-deployed SUAS of less than 50lbs operating at a typical slant range of 1500ft and altitude of 200 feet and higher. The gimbal shall provide broadband NIIRS-6-quality (T) (NIIRS-7 or better (O)) thermal infrared (TIR) imagery (either MWIR or LWIR) with LWIR hyperspectral measurements collected across a broader field-of-view (FOV) with nominally 1.5m (T) ground sample distance (GSD, 1.0m (O)). The LWIR HSI system shall cover a spectral range of 7.5-11um (T) (7.5-13.5um (O)) with adequate spectral resolution, quantified as the full-width half-max (FWHM) of the system spectral response function (SRF), and sensitivity, quantified as noise-equivalent spectral radiance (NESR), to detect a range of military targets for which signatures will be provided. Note, due to the SWaP constraints, solutions may require novel uncooled LWIR systems [2] or scanned point spectrometers using cooled linear detector arrays. The system shall provide on-board processing resources (FPGA, GPU) for integration of gov’t provided algorithms for tracking and/or hyperspectral target detection/ID (T). The gimbal broadband TIR imagery shall be visually lossless after transmission (T). The transmitted chip/frame rate shall be 0.25 hertz (T), 2 hertz (O). Ground coverage of the TIR imagery shall be sufficient to fully encompass the rear aspect of a vehicle, 10x10 feet (T) (20 x 20 feet (O)) at range. The LWIR HSI shall meet an area coverage rate of 5000m2/s (T) (20,000 m2/s (O)). The FOVs shall be operator-steerable over a large part of a lower hemisphere field of regard (T). This effort will not develop entirely new gimbal structures, but will develop a payload, and processing capability. An off-the-shelf gimbal or mature prototype is the expected starting point. This gimbal shall support typical SUAS maneuvering and fly-ins, and shall compensate for disturbances due to gusts and air turbulence. The gimbal should provide accurate line-of-sight pointing data, on-gimbal inertial measurement, and interface to platform GPS (T). 

PHASE I: Identify the hardware requirements for a NIIRS-6-capable 5” TIR gimbal with spectrometer covering the LWIR portion of the spectrum, including stabilization, optics, and focal plane array. Conduct a Systems Requirement Review (SRR). Prepare a preliminary design of the gimbal and payload and hold a preliminary design review (PDR). Use modeling and simulation to justify performance. 

PHASE II: Perform detailed design of the gimbal and payload. Conduct Critical Design Review. Continue modeling and simulation to improve system performance. Based on these results, build a prototype 5” gimbal and payload or breadboard system if budget does not permit full gimbal integration. Evaluate system performance in laboratory and tower (T), and flight test (O) environments. It shall not be assumed that the government will furnish the gimbal for payload integration. However, government facilities and equipment may be used in support of lab and/or tower testing. 

PHASE III: Refine design based on outcomes of tests and customer feedback in Phase II; develop a manufacturing plan and/or select a partner for production of 5” gimbals. 

REFERENCES: 

1. Air Force Unmanned Aerial System (UAS) Flight Plan 2009-2047, http://archive.defense.gov/DODCMSShare/briefingslide/339/090723-D-6570C-001.pdf; 2. P. Lucey, et al, “A compact Fourier transform imaging spectrometer employing a variable gap Fabry-Perot interferometer,” Proc. SPIE, 9101, (2014)

KEYWORDS: SUAS; Imaging; NIIRS, Hyperspectral, Thermal, Longwave; Gimbal 

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