RICHLAND, Wash. - When a U.S. fighter pilot is flying over enemy territory, he must deal with the issue of whether or not his stealth fighter can be detected by radar.
Now, researchers at the Department of Energy's Pacific Northwest National Laboratory have developed a prototype engineering tool to help ease the minds of fighter pilots and their ground crews. The Holographic 3-Dimensional Radar Camera is a hand-held, zone-imaging device that can assist ground crews in verifying the condition of an aircraft's stealth characteristics. The system can be easily deployed worldwide.
Pacific Northwest engineers developed the 3-D radar camera for the U.S. Air Force and recently delivered it to the F-117 System Program Office at Aeronautical Systems Center located at Wright-Patterson Air Force Base in Dayton, Ohio. The system is undergoing evaluation on the F-117A stealth fighter by the 49th Fighter Wing at Holloman Air Force Base in Alamogordo, NM.
This new radar camera will help the Air Force determine the condition of radar-absorbing material on F-117A Nighthawks, and the technology could be applied to other stealth aircraft as well.
The 3-D radar camera works much like a videotape camcorder. The device records images of a portion of an aircraft's radar reflection and translates that information into an image showing where the radar-absorbing material is creating a larger reflection than desired. As an aircraft's radar reflection increases, so do its chances of being detected by enemy radar.
"Ground crews want to verify that the aircraft's radar detectability is low," said Thomas Hall, Pacific Northwest staff engineer. "By using the 3-D radar camera, ground crews can better determine if critical portions of an aircraft are in 'go' or 'no go' condition."
The 3-D radar camera supports pre- and post-repair inspections to ensure the radar-absorbing material is performing as expected, particularly in cases where the aircraft has been damaged, even slightly, during flight.
Pacific Northwest engineers built a Ku-Band radar camera that operates at 12 to 18 gigahertz and delivered it to the F-117 System Program Office in September 1998. The engineers are building a second camera, an X-band camera that will operate at 8 to 12 gigahertz, that is scheduled for delivery this spring.
The Air Force will be able to use both cameras on a single aircraft to measure and characterize any defects in the stealth material. Evaluation across a range of frequencies is important because longer-range search or surveillance radar generally operate on lower frequencies. Shorter-range radar, such as those used by missile and artillery targeting systems, operate on higher frequencies.
"We're providing the ground crew with a new way of helping to verify the stealth condition of an aircraft scheduled for a mission," said Wayne Lechelt, Pacific Northwest staff engineer.
Here's how it works:
The operator holds the camera about two feet from the area to be inspected and "shoots" the aircraft with low-power electromagnetic waves. An antenna array receives the reflected energy and sends it to a computer for processing. Software algorithms translate the level of reflection into a radar image, which then is projected into head-mounted virtual vision glasses. Each snapshot covers a 1-square-foot area.
Through the glasses, the operator sees an image depicting the brightness of the aircraft's radar reflection, or signature. The image displays the radar signature in green, yellow or red to denote pass, assess or fail, respectively. For example, a strong radar signature will appear in red, which means the inspected area has a high level of reflection and would be more visible to radar. Likewise, a yellow "assess" reading will appear if the radar-absorbing material has been degraded but not necessarily enough to require immediate repair.
Pacific Northwest engineers designed the radar camera to protect classified information during operation. By using virtual vision goggles, the operator is the only person who sees the radar images. The radar camera has no internal storage component that would require securing the device in a classified area. Instead, the operator can choose to download images onto a removable disk for later analysis and processing.
The F-117 System Program Office at Wright-Patterson Air Force Base funded design and development of the cameras with $1.2 million, in collaboration with the Air Force Research Laboratory.
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Pacific Northwest is one of DOE's nine multiprogram national laboratories and conducts research in the fields of environment, energy, health sciences and national security. Battelle, based in Columbus, Ohio, has operated Pacific Northwest for DOE since 1965.