Missile defense

Missile defense comprises systems and operations that detect, track, intercept, or otherwise defeat incoming missiles before they reach their targets.

Early-warning radar: Radar systems detect distant aircraft and missiles, providing warning of potential attacks. Radar can detect launches and incoming objects early enough to support a defensive response.
Ballistic missile: A missile that follows a largely ballistic trajectory after its powered flight phase. Ballistic missiles are a central target of strategic missile-defense systems.
Aegis Ballistic Missile Defense: A United States Navy system that uses Aegis combat-system ships and interceptor missiles against ballistic threats. It provides a mobile, sea-based layer of missile defense.
Mutual assured destruction: A deterrence condition in which opposing nuclear powers can each inflict unacceptable damage after a first strike. Robust defenses could appear to weaken the retaliatory threat on which this deterrence rests.
Missile tracking: The process of estimating a missile’s position, velocity, and trajectory over time. Interceptors depend on accurate tracks to predict where an incoming missile will be.
Cruise missile: A guided missile that flies through the atmosphere using aerodynamic lift for much of its route. Its low-altitude, maneuvering flight creates different detection and interception problems.
Ground-Based Midcourse Defense: A United States system designed to intercept limited intercontinental ballistic missile attacks during midcourse flight. It is a homeland-defense system built around ground-launched interceptors.
Anti-satellite weapon: A weapon designed to disable or destroy satellites in orbit. Some technologies overlap with missile interception, but the target and operational purpose differ.
Command and control: The systems and procedures that coordinate decisions and actions across military forces. Defenders must combine sensor data and authorize engagement within tight time limits.
Boost phase: The portion of a rocket’s flight when its engine is accelerating it after launch. A bright, powered missile is potentially easier to detect, but the interception window is brief.

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