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Real-time Location of Targets in Cluttered Environments


OBJECTIVE: To develop a process for real-time radar location of targets in cluttered environments, specifically air traffic targets in environments complicated by complex natural (e.g., hills and valleys) and manmade (e.g., wind turbines) features. DESCRIPTION: Our nation is developing a diverse range of renewable energy projects. Some of these energy production sites are located near existing military bases or military test ranges. Furthermore, it has been observed that operation of these energy production sites can confound military equipment or otherwise negatively impact training or operational readiness. A prime example is the impact of interference to air traffic radar operation caused by the reflection of the air traffic radar signal from rotating wind turbine blades. Two broad classes of error can occur: one is false positives or targets which are produced by the scatter of radar signals from rotating blades and can be misinterpreted by radar systems as weather or aircraft; the other is false negatives or dropped targets which corresponds to a loss of radar signal strength and can cause the masking of actual air traffic radar returns. Note that the engineering standard for probability of target detection is 80%. Additional complications arise because of static clutter (examples of which are terrain and topography features, wind turbine masts, etc.) and dynamic clutter (examples of which are the spinning blades attached to these wind turbine masts together with the extra complication of slight vibrations, various rotation speeds, and orientation changes exhibited by the spinning blades). A first step in addressing this problem is to characterize and define the clutter. The second step would be to be able to extract information and signals from the radar reflections provided by moving targets in the clutter environment. To this end a modeling and simulation undertaking wherein the Maxwell's equations are solved for the scattering (from moving objects with correct Doppler shifts) of varioius radar signals is solicited. This undertaking should include careful error analysis of the numerical approach so that a third broad class of error in addition to the two mentioned above isn't introduced. Because the target could be masked during its track by terrain or wind turbines, both line-of-sight and non-line-of-sight methods are appropriate where it is to be understood that the latter is a source of multipathing. PHASE I: Efforts should concentrate on the development of a mathematical construct for the characterization of the clutter environment. Fixed features will result in static clutter terms, but the construct should account for dynamic (e.g., spinning turbine) terms. Some consideration for inclusion of moving targets would be useful. PHASE II: Efforts should expand the methodology of Phase I to address the detection of targets in the clutter field. This should account for targets within appropriate ranges of altitude, speed, and track trajectories. The probability of detection as demonstrated by simulation or actual flights should exceed the 80% standard. PHASE III: Adoption into military air traffic control radar systems is anticipated. Transition to civil airports or high-traffic corridors serviced by current radar systems should be a goal. REFERENCES: 1. Steinhoff, J., Chitta, S., (2010)"Long distance wave computation using nonlinear solitary waves", Journal of Computational & Applied Mathematics, 234(6), 1826-1833. 2. Steinhoff, J. and Chitta, S. (2010)"Long-time solution of the wave equation using nonlinear dissipative structures", Chapter 32 in Integral Methods in Science and Engineering, Volume 2, pages 339-349. 3. S. Chitta, P. Sanematsu, J. Steinhoff, (2011)"Nonlinear Localized Dissipative Structures for Solving Wave Equations over Long Distances", Chapter 33 in Integral Methods in Science and Engineering: Computational Methods and Analytic Aspects.
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