Synthetic aperture radar helps detect IEDs in all conditions
The technology was developed with the Defense Department’s Joint Improvised Explosive Device Defeat Organization (JIEDDO); the U.S. Army Engineer Research and Development Center/Cold Regions Research and Engineering Laboratory (CRREL); the Naval Air Systems Command (NAVAIR); Johns Hopkins University’s Applied Physics Laboratory; the Naval Research Laboratory; and Florida-based force protection company AIRSCAN.
"JIEDDO tested a number of technologies and ours emerged as one that was viable," Hudgens said. "Today, we’re acknowledged as the most successful airborne IED detection capability out there."
Copperhead detects disturbances in the earth, for example, those made when IEDs are buried. It can find them day or night and in many weather conditions, including fog and dust storms. Extremely fine-resolution images are processed onboard UAVs and transmitted real-time to analysts on the ground. Those analysts pass the information to soldiers charged with destroying IEDs.
Sandia National Laboratories’ highly modified miniature synthetic aperture radar system is being transferred to the US Army to support combat military personnel by uncovering improvised explosive devices. Photo courtesy of Sandia National Laboratories.
Though IED detonations have declined in Afghanistan since a peak of more than 2,000 in the month of June 2012, Department of Defense reports indicated IEDs accounted for about 60 percent of U.S. casualties that year.
SAR and its descendent MiniSAR, the first system of its size to successfully transmit real-time images from UAVs in 2006, use small antennae that capture reflections of microwaves returned from objects on the ground, transmitting and receiving many radar pulses as the aircraft flies. The received pulses are integrated by signal-processing techniques to synthesize a fine-resolution image, hence the name "synthetic aperture."
Hudgens and Sandia manager Bill Hensley say had it not been for Sandia’s research and development process funded, in part, by the Laboratory Directed Research and Development program, to reduce the size of the SAR that led to MiniSAR, Copperhead might never have been ready in time to help the Army.
Just as cameras are limited by depth of field — where a near object is in focus but the background is blurry or vice versa — MiniSAR needed a way to keep the entire height of the terrain in an image in focus, for example, the top of a mountain and the valley floor.
To address this, advanced image-processing algorithms were created that focused the high and low terrain simultaneously while continuing to provide fine-resolution imagery. The new capability, which has been proven effective on slopes of more than 40 degrees, made Copperhead useful in the wide variety of terrain present in places like Afghanistan.
Copperhead uses a technology called coherent change detection, which compares a pair of extremely detailed SAR images taken of the same scene but at different times. The process allows analysts to detect minute physical changes on the surface.
"There are other approaches to change detection out there, but this is the only one that’s all-weather," Hudgens said.
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