Fire-and-Forget Missile Guidance

A fire-and-forget missile needs no guidance commands from the launcher after firing. Its onboard sensors, navigation system and computer form an autonomous guidance system that estimates the missile's position, tracks a target or stored location, and commands course corrections.

The autonomous guidance loop

Autonomy comes from a closed loop linking sensors, computation and flight controls.

• Before launch, the weapon receives a target lock or stored target data through lock-on-before-launch or lock-on-after-launch arrangements.
• An onboard inertial navigation system estimates the missile's motion during initial or midcourse flight.
• The seeker, such as imaging infrared or active radar, measures the target's direction and tracking error.
• The guidance computer calculates the required course correction, while the autopilot moves fins or controls thrust; this loop repeats until impact.

Ways of reaching the target

The precise method depends on the missile's seeker and intended target.

• A homing missile continuously tracks a target through a passive infrared, active radar or combined seeker.
• In lock-on-after-launch, inertial guidance first carries the missile towards the target area, where its terminal seeker acquires the target.
• A coordinate-guided weapon uses INS, often aided by satellite navigation, to reach a stored position without continuously sensing a target.

Meaning and limitations of autonomy

Fire-and-forget removes the need for post-launch commands, but it does not make guidance infallible.

• The launcher can relocate or engage another target because no continuous datalink or operator steering is required.
• Performance can be degraded by obscuration, background clutter, decoys or electronic countermeasures, depending on the seeker.
• A purely coordinate-guided missile cannot follow a target that leaves the stored location unless it also has terminal homing.