N122-141 TITLE: Predictive Model for Imaging Underwater Objects through the Air-Sea Interface

TECHNOLOGY AREAS: Sensors, Battlespace

ACQUISITION PROGRAM: PMS-495; SHD12-04 "Detection and Neutralization of Drifting Mines"

OBJECTIVE: To develop a radiative transfer model to predict visibility of submerged objects by above-surface sensors accounting for realistic sea surface geometry as well as water column and seafloor characteristics.

DESCRIPTION: Detection of underwater objects by above-surface passive and active electro-optic (EO) sensors is required for a variety of DoD and civilian applications. Existing models crudely parameterize the complex, time-dependent sea surface geometry, which may include wave-breaking, sea foam, and surfactants. Detailed multi-scale models for sea surface geometry are now available; likewise, in situ instruments provide water column properties including inherent optical properties, suspended sediment, biologics, and bubbles. Finally, in shallow environments the optical properties of the seafloor can impact the ability of a sensor to detect submerged objects near the sea surface, in the water column, or on the seafloor. Robust, high-fidelity, algorithmic approaches and modular software for predicting the time-varying visibility of submerged objects having arbitrary optical and geometrical properties should be developed to address: 1) a high-fidelity treatment of the geometry and properties of the air-sea interface, including foam and surfactants, 2) a description of the water column including suspended sediment, biologics, and bubbles, 3) a description of relevant seafloor properties, and finally, 4) estimates of uncertainty for the derived environmental characteristics.

PHASE I: Develop a plan, based on current state-of-the-art knowledge of oceanographic phenomena, to build and validate an EO radiative transfer model to predict time-varying visibility of submerged objects having arbitrary optical and geometrical properties using sensors located above the sea surface. The plan should, at a minimum, address the plan for software modularity, modeling of the relevant oceanographic/radiative transfer phenomena, development of algorithms, implementation of computer code, and methodology for estimation of prediction uncertainties.

Develop an algorithmic strategy and software modules to address topic objectives that are compatible with Navy Mine Warfare (MIW) Command and Control (C2) software systems. Demonstrate efficacy of selected algorithms across a wide range of the multi-dimensional parameter space by comparison to existing laboratory and field measurements. Describe data input requirements and output products, including treatment of uncertainty in input parameters.

PHASE II: Develop algorithms and implement a set of modules, in computer code, addressing each of the components of the radiative transfer problem described in Phase I. Develop plans for, and implement in computer code, the ability to: 1) visualize the results, 2) implement underwater targets with arbitrary geometry, optical properties, and location within the water column, and 3) implement the capability to select from active and passive sensors having a broad range of characteristics. Test simulation predictions using available data from the literature or other existing data. Develop interface control documentation for MIW C2 Mine Warfare and Environmental Decision Aids Library � Enterprise Architecture (MEDAL-EA), Environmental Post-Mission Analysis (EPMA) and Network-centric Sensor Analysis for Mine Warfare (NSAM) and control software and demonstrate compatibility with those systems.

PHASE III: Transition MIW C2 compatible modular software to US Navy and/or US Marine Corps program of record.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Models for prediction of radiative transfer through the air-water interface have application to a wide variety of civilian engineering and scientific applications. These applications include, among many others: remote sensing of water depth in nearshore waters, reefs, and rivers; airborne measurement of the opacity of turbid water due to suspended particles, surfactant films, and foams; and, the impact of changes in water optical properties and the impact of such changes on ocean biota.

REFERENCES:
1. Mobley, Curtis D. 1994. Light and Water: Radiative Transfer in Natural Waters. San Diego: Academic Press.

2. McLean, John W., and Jonathan D. Freeman. 1996. "Effects of Ocean Waves on Airborne LIDAR Imaging." Applied Optics 35, no. 18: 3261-3269. Accessed December 2, 2011. doi: 10.1364/AO.35.003261.

3. Zaneveld, J. Ronald V., Emmanuel Boss, and Andrew Barnard. 2001. "Influence of Surface Waves on Measured and Modeled Irradiance Profiles." Applied Optics 40, no. 9: 1442-1449. Accessed December 2, 2011. doi: 10.1364/AO.40.001442.

4. Walker, Ronald E., Marine Light Field Statistics. New York: John Wiley & Sons, Inc.

5. Stramski, Dariusz, Emmanuel Boss, Darek Bogucki, and Kenneth J. Voss. 2004. "The Role of Seawater Constituents in Light Backscattering in the Ocean." Progress in Oceanography 61, no. 1: 27-56. Accessed December 2, 2011. doi: 10.1016/j.pocean.2004.07.001.

6. Cramer, Megan, Vic Leung, and Tom Davilli. 2010. "MEDAL EA: Mine Warfare and Environmental Decision Aids Library, Enterprise Architecture". Presented at the Mine Warfare Association Symposium, Monterey, California, May 18, 2010. Accessed January 17, 2012. http://www.9thsymposium.com/art_symposium/presentations/Davilli.pdf.

7. Stack, Jason. 2011. "Automation for Underwater Mine Recognition: Current Trends & Future Strategy", Proceedings of the SPIE Defense and Security Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVI Conference, volume 8017. Accessed January 17, 2012. doi: 10.1117/12.884475.

KEYWORDS: Underwater imaging; ocean optics; electro-optical; radiative transfer; air-sea interface; surface gravity waves

** TOPIC AUTHOR (TPOC) **

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