A New Airborne Weather Instrument Based on Digital Holography

The problem is to develop a compact instrument to measure cloud droplet-drizzle in the range of 10 to 1,000 m from unmanned airborne vehicles (UAVs) (such as the ScanEagle or Puma) in the Arctic and Antarctic regions. As stated in the SBIR solicitation, traditional packages are too large and heavy for this application. The instrument should have little or no pressure control, weigh less than 5 kg and operate with under 50 watts. Statement of How this Problem or Situation is Being Addressed We propose to develop a digital scanning holographic camera for atmospheric particle sampling. Airborne holography systems have flown successfully for many years (by the current proposers and others); however, the current requirement cannot be met by existing systems because of size and weight restrictions. With a UAV, the diffraction field moves over the detector array. We propose to exploit that movement, allowing the object field to sweep the diffraction pattern over a linear detector array, a principle that is already proven in digital holography. The linear detector array samples and digitizes the diffraction pattern of the particles as they move over the array, producing the same information that can be captured on a two-dimensional array, but doing it continuously. Linear arrays can be operated much faster than two-dimensional arrays, are easier to protect using smaller windows, and require less weight and power to operate. Data from extremely large sample volumes can be stored on a small memory card and processed by computer later. The project will enable digital holography from balloons and unmanned airborne vehicles (UAVs) with unique concepts that can reduce the camera size and power requirement, increase the sample volume, and process data more efficiently. This will represent a major advance in the art of digital particle holography. The proposed concept adds capabilities that are not currently available, such as accurate concentration measurements. Since holograms contain 3-D position information, a holocamera will outperform most existing instrumentation in concentration and size measurement. MetroLaser, Inc. Topic 19.a A New Airborne Weather Instrument Based on Digital Holography 2 P1421DEJT_Summary Commercial Applications and Other Benefits The proposed diagnostics tool will have many applications in future meteorology experiments, providing investigators a presence in extremely remote locations via a virtual holographic window. The proposed instrument would enable measuring clouds and aerosols in the Arctic and Antarctic regions, which play a significant role in the prediction of global warming. In addition to atmospheric measurements, the proposed instrument would be applicable to numerous commercial applications associated with sprays such as combustion engine injector design, agricultural spray characterization, and the characterization and design of spray fire extinguishers. Key Words Particle sizing, cloud characterization, airborne, digital holography Summary for Members of Congress New instruments are needed to more accurately characterize the atmosphere and provide critical data for climate science. This work specifically addresses the need for ice, water, and other particle measurements in the atmosphere, especially in the Arctic and Antarctic regions. Compact instruments that can be deployed in unmanned aerial vehicles are needed to measure cloud particles in the range of 10 to 1,000 m. Traditional instruments are too large and heavy for this application. The instrument should have little or no pressure control, weigh less than 5 kg and operate with under 50 watts. One of the most powerful particle field characterization tools is 3D holography, which allows a researcher to examine and characterize microscopic particles in large volumes. Traditional systems, though powerful in capability are much too large and heavy and consume too much power to be deployed in UAVs. However, in recent years, the emergence of digital optics and electronics changes this situation entirely. Digital holography records holograms electronically and stores them in memory cards. Particle field images are reconstructed electronically by high speed computers. It should be possible to incorporate these methods into a small, rugged, lightweight, low power instrument that is capable of providing critical measurements that are not provided by any other technology. The objective of this research is to prove the feasibility of such an instrument in Phase I and to construct and field it in Phase II.