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How can a missile's exhaust plume affect signals received by over-the-horizon radar?
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warning system
U.S. Air Force Boeing E-3 Sentry, an airborne warning and control system (AWACS) aircraft.
Over-the-horizon (OTH) radar systems, which operate in the high-frequency (HF) radio band, detect ballistic missiles by monitoring the ionosphere for specific disturbances.12
When a ballistic missile traverses the ionosphere, its exhaust plume creates fluctuations in the ionized medium. These fluctuations cause detectable variations in the signals received by the radar. By identifying these ionospheric disturbances, OTH radar systems—including both forward-scatter and back-scatter configurations—can provide early warning of missile activity before the target is visible above the Earth's horizon.2