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Why can radar detect phenomena that are not solid aircraft?
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unidentified flying object
Learn about an unidentified aerial phenomena (UAP) sighting from this video (known as the Gimbal video) captured by fighter pilots associated with the USS Theodore Roosevelt carrier strike group. The video shows instrument detections of unknown aerial objects, which the pilots were unable to identify, off the East Coast of the United States, 2014–15.
Radar systems detect non-aircraft phenomena because they are designed to reflect electromagnetic energy off a wide variety of objects and environmental conditions. Anything that reflects radar waves can produce an echo, which radar operators often categorize as "clutter" when it interferes with the detection of intended targets like aircraft or ships.12
These non-solid or non-aircraft detections occur due to several factors:
- Atmospheric and Environmental Conditions: Precipitation such as rain, snow, and hail reflects radar energy. Additionally, atmospheric "ducts"—layers of air that trap and guide radar waves—can cause signals to bend around the Earth's curvature, leading to detections at ranges beyond the normal horizon.23
- Biological and Natural Objects: Radar is sensitive enough to detect birds, insects, and even meteors. Advanced systems can sometimes distinguish these from aircraft by analyzing specific characteristics, such as the modulation produced by the flapping of a bird's wings.24
- Surface Reflections: Reflections from terrain, land, or disturbed sea surfaces are common sources of clutter that radar circuitry must filter out to maintain a clear view of desired targets.1
Designers use techniques like Doppler filtering and circular polarization to separate these unwanted echoes from aircraft targets.52