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Measuring Ground-to-Air Atmospheric Path Transmission


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Integrated Sensing and Cyber The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Design and fabricate a device that can measure the ground-to-air atmospheric transmission path for electromagnetic waves in the wavelength range of 0.2 µm – 14 µm. This device will improve the accuracy and reliability of infrared signature measurements. DESCRIPTION: It is important to account for the atmospheric conditions when collecting infrared signature data. Infrared radiation is absorbed and scattered by atmospheric gases, water vapor, and aerosols, which can affect the accuracy and reliability of the measurements. To obtain accurate data, it is necessary to account for the atmospheric temperature, pressure, humidity, and aerosol content, and to correct for their effects on infrared radiation. The current method of doing this is to deploy a weather balloon on site and feed that data into a modeling software called MODTRAN (MODerate resolution atmospheric TRANsmission). MODTRAN will generate a transmission path factor, otherwise known as a tpfact. The tpfact is defined as the ratio of the effective path length of the radiation through the atmosphere to the total path length. When acquiring infrared signature data, the tpfact becomes a part of the calculation that converts a raw image into one that displays temperature and radiance. MODTRAN has been a useful tool, but it has its limitations. Simulating the atmospheric transmission path relies on mathematical models and assumptions that may not reflect the actual conditions present during data capture. Direct measurement of the transmission path will result in a more accurate representation of complex interactions and phenomena within the atmosphere. This will serve to significantly improve the quality of infrared signature data. The goal for this project is to measure how radiation from an airborne target is attenuated by atmospheric conditions. To achieve this, a blackbody and a spectrometer would need to be configured so that one is attached to an airborne platform and the other is placed at the collection site. The platform would need to loiter at the same altitude as the target under test. The desired platform altitude is 10,000 feet AGL or more, but a minimum threshold of 1,000 feet AGL is acceptable. The challenge will be to find an airborne platform that can carry the payload and collect/calibrate atmospheric attenuation data. PHASE I: In Phase l, the awardees will determine the feasibility of attaching a blackbody or spectrometer to an unmanned aircraft. Questions for which answers will be sought include: 1. What types of spectrometers and blackbodies would need to be used for the spectrometer to gather data from multiple miles away? 2. What type of aircraft is suited to carry the proposed blackbody/spectrometer? 3. How will the data from the spectrometer be recorded? 4. What training, certifications, and FAA approvals will be necessary? PHASE II: The questions answered in Phase l will serve as the foundation for the prototype delivered in Phase ll. The prototype will be some sort of aircraft capable of flying at least 1,000 feet AGL while carrying either a spectrometer or blackbody. The delivered device will be tested to confirm that the spectrometer is pointed at the blackbody, recording data in the wavelength range of 0.2 µm – 14 µm, and that the data can be used to perform an atmospheric correction on infrared signature dat PHASE III DUAL USE APPLICATIONS: The proposed aircraft can be adapted to fit a wide variety of needs within the DoD. The device will also provide valuable data that could be of interest to various academic institutions and weather organizations. In Phase lll, efforts will be made to identify any other organizations who might be interested in using this device. REFERENCES: 1. 1. Berk, A., P.K. Acharya, L.S. Bernstein, G.P. Anderson, P. Lewis, J.H. Chetwynd, and M.L. Hoke, "Band Model Method for Modeling Atmospheric Propagation at Arbitrarily Fine Spectral Resolution" KEYWORDS: Infrared ; Spectrometer ; UAV ; Airborne Platform ; Ultra-violet ; Midwave Infrared ; Longwave Infrared ; MWIR ; LWIR ; UV
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