What are angel echoes
Angel echoes, also known as "angels" or "invisible echoes," are radar echoes that appear on radar screens but are not caused by physical objects like aircraft, vehicles, or weather phenomena. These echoes are typically caused by natural atmospheric conditions or biological sources. Here are the primary causes of angel echoes:
Causes of Angel Echoes
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Atmospheric Turbulence: Variations in temperature, humidity, and pressure can create small-scale turbulence in the atmosphere. These turbulent areas can reflect radar signals, creating echoes on the radar screen.
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Inversion Layers: Temperature inversion layers, where a layer of warm air sits above cooler air, can create sharp boundaries in the atmosphere. These boundaries can reflect radar waves, resulting in angel echoes.
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Biological Sources: Large flocks of birds, swarms of insects, or even bats can create radar echoes. These biological sources can produce returns that appear similar to those from small aircraft or other objects.
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Ionospheric Reflections: Under certain conditions, radar waves can be reflected by the ionosphere, the ionized part of Earth's upper atmosphere. This can cause radar returns from distant sources, creating false echoes.
Characteristics of Angel Echoes
- Intermittent and Variable: Angel echoes can appear and disappear rapidly and may vary in intensity and position.
- Non-linear Movement: Unlike aircraft or weather patterns, which tend to move in predictable paths, angel echoes can move erratically or remain stationary.
- Lack of Correlation with Visible Objects: Angel echoes do not correspond to any visible objects or known sources on the ground or in the air.
Implications
- Radar Interpretation: The presence of angel echoes can complicate the interpretation of radar data, as operators must distinguish between real targets and these false returns.
- Aviation Safety: In air traffic control and aviation, distinguishing angel echoes from real aircraft is crucial to ensure safety and accurate tracking.
Understanding the causes and characteristics of angel echoes helps radar operators filter out these false returns and focus on genuine targets, improving the accuracy and reliability of radar systems.
