TECHNOLOGY AREAS: Ground/Sea Vehicles, Sensors, Battlespace

OBJECTIVE: Develop a physics-based model describing the generation of remotely-detectable small-scale ocean surface roughness anomalies caused by nonlinear interactions between impulsive acoustic/hydrodynamic sources and background ocean inhomogeneities.

DESCRIPTION: Wind and current variations at the mean surface can give rise to a modulation of the ocean surface roughness and thus can become visible in optical and radar images. For example, the capacity of optical and radar sensors to image bathymetry features in tidally dominated coastal areas is well established. Although microwave radiation cannot penetrate the ocean by more than a few millimeters, underwater features appear clearly as bright and/or dark patterns in radar images. In fact, there are many ocean phenomena that can generate detectable alterations in radar imagery. Among them are ocean swells, oil slicks, wind slicks, currents, internal waves, eddies, and ship wakes.

Investigation is needed in the interaction of weak natural and man-made sources of impulsive acoustic/hydrodynamic energy with a marginally stable ocean background environment in a nonlinear fashion to produce small-scale ocean surface roughness changes of sufficient amplitude and spatial extent to be visible optically and by microwave radar. A physical understanding of the signature generation mechanism along with the spatial and temporal characteristics of the surface roughness modulation is sought. The ability to discriminate between the signature of interest and signatures of other oceanic and atmospheric phenomena is critical.

PHASE I: Provide and justify the taxonomy for the nonlinear interaction between impulsive acoustic/hydrodynamic sources and background ocean inhomogeneities.

PHASE II: Develop analytical and computational models and perform simulations that might lead to an understanding of the important phenomena and interactions from Phase I. Provide a plan for further analytical investigation of key issues and a plan for the experiments that will provide data for these issues. Develop test specifications for equipments, sites, and environmental needs, and develop hypothetical test plans for measurements required to validate the simulations of merit.

PHASE III: Continue the development of the analytical and computational model and perform the validation experiments and analyses. Working with sensor system OEMs, develop real-time detection algorithms suitable for evaluation in an operationally representative test environment. A sensor system utilizing proven detection algorithms could be utilized in applications of interest to the Navy as well as civilian environmental applications.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Potential dual use applications include ocean environmental assessments, physical oceanography, biological and chemical oceanography, ocean modeling and prediction, tactical environmental support, and marine meteorology.

REFERENCES:
1. Clemente-Colon, P.; Xiao-Hai Yan, "Observations of East Coast upwelling conditions in synthetic aperture radar imagery," Geoscience and Remote Sensing, IEEE Transactions on, Volume 37, Issue 5, Sep 1999 Page(s):2239-2248.

2. Dennis B. Trizna, David J. Carlson, "Studies Of Dual Polarized Low Grazing Angle Radar Sea Scatter In Nearshore Regions," IEEE Transactions On Geoscience And Remote Sensing, Vol. 34, No. 3, May 1996, Page(s): 747-757.

3. T. F. N. Kanaa, G. Mercier, E. Tonye, Sea Surface Slicks Characterization in SAR Images, Oceans - Europe 2005, 20-23 June 2005, Page(s): 686-691.

KEYWORDS: Nonlinear Interaction; Impulsive Acoustic/Hydrodynamic Sources; Natural Ocean Inhomogenities; Ocean Modeling and Prediction; Marine Science; Oceanography