Detection/Imaging of Buried Objects: Using Spatial/Angular Diversity with Distributed/Embedded Sub-Surface Sensors for Reduced Mutual Coupling and Suppressed EM Emissions

The proliferation of strategic subsurface sanctuaries has increased the need for enhanced remote sensing techniques providing for the accurate detection and identification of deeply buried objects. A new RF Tomographic Technique is proposed in this concept paper for developing RF CAT Scans of buried objects using spectral, spatial/angular, and polarization diversity. This imaging technique uses an embedded ring of subsurface radiators, delivered by earth-penetrating, non-explosive, electronic "e-bombs", as the source of strong underground radiated transmissions and uses distributed surface-contact sensors to collect the tomographic data for relay to a circling UAV and transmission to a remote control site (using layered sensing). Three-dimensional imaging algorithms are being developed to detect, image, and characterize deeply buried targets. Distributed transmitters and receivers significantly increase unwanted mutual coupling and EM emissions that interfere with signal reception. However, by embedding the transmitters underground, reduced mutual coupling and EM emissions (and improved signal-to-noise ratios) can be achieved. Simple surface SAR experiments over deep mine shafts have been performed to validate the 3D processing algorithms using 2D surface SAR sensor data. WIPL-D models have also been used to simulate the embedded and distributed sensors and to verify the significant enhancement in the received signal-to-noise ratio obtained by burying the radiating ring under the surface sensors.