N23A-T012   TITLE: Atmospheric Aerosol Model and Data Collection Over the Marine Boundary Layer for Imaging/Radiofrequency (RF) and Laser Beam Propagation

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Directed Energy (DE); General Warfighting Requirements (GWR)

OBJECTIVE: Develop a periscope imaging, electronic warfare, and High Energy Laser (HEL) beam propagation model over the marine aerosol boundary layer for the integration of propagation modeling software into a system that will investigate absorption and scattering properties of marine aerosols, the interplay between aerosols and turbulence, and the impact on imaging and electronic warfare (EW).

DESCRIPTION: The Navy seeks technologies that are oriented toward a deeper experimental and theoretical understanding of maritime turbulence and laser beam propagation in the marine boundary layer (MABL). Ocean evaporation is occurring within a very thin molecular layer at the surface. However, there are indications that instantaneous turbulent structures in the ocean and marine atmospheric mixing layers play a critical role in determining the water vapor flux and near surface particulate (aerosol) concentrations. The Navy is looking for a greater understanding of the marine aerosols and their impact on turbulence on periscope imaging, EW, and HEL beam propagation. Aerosol properties will be studied using available instruments such as particle counters, sun photometers, Short Wave Infrared (SWIR) cameras, Delayed Tilt Anisoplanatism (DELTA) camera, RAMAN scattering instrument, and instruments for aerosol absorption quantification. This proposed study will help improve the current atmospheric models for submarine imaging/ EW and HEL horizontal beam propagation within the MABL. Recent efforts have been aimed at characterizing the turbulence in the marine wave layer and surface layer marine boundary layer. The aerosol and turbulence models developed through experimental measurements will be used to model nonlinear effects such as thermal blooming in a marine environment on both continuous and pulsed lasers. Additionally, image contrast reduction due to marine aerosols will be studied and the prospect of determining aerosol loading from degraded images will be investigated. In this proposed study and model, we are looking for an innovative instrument development to understand the nonlinearity of the atmosphere like thermal blooming and RAMAN scattering. The model developed shall include atmospheric nonlinearity and its effects on a complete model of Imaging and HEL beam propagation that includes turbulence and aerosol effects. The model will be extremely useful for development of adaptive optics and beam control systems to maximize power in the bucket in case of horizontal propagations.

In this STTR topic the proposer shall explore the use of a small Unmanned Aircraft System (sUAS) and develop and execute sUAS flight profiles for marine Sea-Air turbulence and aerosol interface research. Marine boundary layer profiling at different heights shall be used to enhance the multi-target capability of a customer�s imaging and on HEL as well as the HEL subsystem�s including laser range finders (LRFs), and beacon and tracker illuminator lasers. Additionally, such profiling in combination with radiative transfer and Imaging and HEL propagation models such as the Laser Environmental Effects Definition and Reference (LEEDR) and High Energy Laser End to End Operational Simulation (HELEEOS) codes shall enhance post-engagement HEL forensic analysis such as target effects in the marine boundary layer.

Current measurement techniques, such as Laser Doppler Velocimetry (LDV), are limited to resolutions of 0.5 meters or greater and fall short of the required millimeter level resolution. A new type of spectral imaging modality and instrumentation is required that will increase our understanding of ocean evaporation and lead to better tools for measuring and modeling the near-marine boundary layer for optical and radio frequency Naval applications. This generalized understanding will significantly enhance beam optic directors, adaptive optics, and other turbulence mitigating techniques to enhance the reach and effectiveness of communication as well as defensive and offensive high energy laser engagement in the marine aerosol boundary layer.

PHASE I: Provide a concept to solve the Navy�s problem, and demonstrate the feasibility of that concept. Develop the general model concept and instrumentation setup over MABL to collect data for the prediction atmospheric non linearity and its effects such as marine thermal blooming and other marine non linear effects due to image degradation and HEL horizontal beam propagation through the MABL < 60 ft above marine surface. Develop clear model concepts and non-linear MABL data acquisition setup to remotely measure temperature, pressure, and marine aerosol for the acquisition MABL model validation and verification. Phase I Option, if exercised, will include the initial model and capabilities description to build a prototype model and validation of the proposed model by data collection over marine surface in Phase II.

PHASE II: Develop the marine aerosol on image degradation and HEL Beam propagation model and data collection analysis software which shall be delivered to Navy. The MABL model shall be used for submarine imaging system and target detection and tracking, HEL target lethality improvement and integration with submarine HEL beam control software for evaluating HEL horizontal beam propagation and image degradation through marine aerosol environment. The model shall be used for system performance evaluation based on the results of Phase I concepts. Describe how evaluation can be accomplished through modeling or non-linear analytical methods to demonstrate that the technology does have the potential to meet Navy imaging, such as image degradation, target detection, target identification, and HEL performance goals such as remotely profile horizontal turbulence profile mapping, temperature, and pressure profile mapping.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology to Navy submarine platforms as a metrological tool for marine wave boundary data collection.

The non-liner marine aerosol effects on Submarine Imaging and HEL beam propagation model and innovative data analysis technology such as Fourier Optical analysis have both commercial and DoD applications. This technology can improve a commercial ship�s localized weather prediction and update the weather software for safe operation. Additionally, improved LIDAR detection for range at day, night, and all-weather conditions is beneficial for both commercial and DoD applications. The nonlinear marine aerosol metrology model system could also find applications in trace gas and pollution monitoring.

REFERENCES:

1.       Wasiczko Thomas, Linda M., Moore, Christopher I., Burris, Harris R., Suite, Michele, Smith Jr., Walter Reed, and Rabinovich, William. "NRL's Research at the Lasercomm Test Facility: Characterization of the Maritime Atmosphere and Initial Results in Analog AM Lasercomm", Proc. SPIE, 6951, Atmospheric Propagation V, 69510S (April 18, 2008). https://doi.org/10.1117/12.783791

2.       David N. Whiteman, "Examination of the traditional RAMAN lidar technique. I. Evaluating the temperature-dependent lidar equations," Appl. Opt. 42, 2571-2592 (2003) https://doi.org/10.1364/AO.42.002571

3.       David N. Whiteman, "Examination of the traditional RAMAN lidar technique. II. Evaluating the ratios for water vapor and aerosols," Appl. Opt. 42, 2593-2608 (2003) https://doi.org/10.1364/AO.42.002593

4.       Chunhua Deng , Sarah D. Brooks , German Vidaurre & Daniel C. O. Thornton (2014) Using RAMAN Microspectroscopy to Determine Chemical Composition and Mixing State of Airborne Marine Aerosols over the Pacific Ocean, Aerosol Science and Technology, 48:2, 193-206, DOI: 10.1080/02786826.2013.867297 https://www.tandfonline.com/doi/full/10.1080/02786826.2013.867297

 

KEYWORDS: RAMAN; Laser Beam Propagation; Marine Aerosol Environment; Marine turbulent boundary Layer; MABL; Thermal blooming; Laser Environmental Effects Definition and Reference; LEEDR

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