- Command guided
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Command guidance is a type of missile guidance in which a ground station or aircraft relay signals to a guided missile via radio (or possibly through a wire connecting the missile to the launcher) and tell the missile where to steer in order to intercept its target. Additionally, it is possible to send a command to the missile to detonate, even if the missile itself has a fuze or fuzes. (It may be possible to detonate the missile and destroy or damage the target, even though the missile was not actually going to strike the target, due to the blast radius of the warhead).
Typically, the system giving the guidance commands is tracking both the target and the missile or missiles via radar. It determines the position and velocity of the target and the position and velocity of the missile and calculates whether their paths will intersect. If not, the guidance system will relay commands to the missile(s), telling them to move their fins in such a way to steer themselves in the direction necessary for them to end up on an interception course with the target. If the target maneuvers, the guidance system can notice this and update the missiles' course continuously to counteract the maneuvering. If the missile passes close to the target, either its own proximity or contact fuze will detonate the warhead, or the guidance system can estimate when the missile will pass near the target and send a detonation signal.
On some systems there is a dedicated radio antenna or antennas for communicating with the missile(s). On others, the radar itself is actually able to send coded pulses which the missile can pick up and interpret as guidance commands. Sometimes to aid the tracking station, the missile will contain a radio transmitter, making it easier to track. Also, sometimes there is a dedicated radar antenna on the tracking station for tracking the missile as well as one or more for tracking targets. It is especially these types of systems which may be able to communicate with the missile via the same radar energy it uses for tracking it.
Examples of missiles which use command guidance include:
- Russian: SA-1 'Guild', SA-2 'Guideline', SA-3 'Goa', SA-15 'Gauntlet'
- American: Nike Ajax, Nike Hercules, Nike Zeus
Note that older western missiles tended to prefer using pure semi-active radar homing.
Pure command guidance is not normally used in modern SAM systems since it is too inaccurate during the terminal phase (when the missile is about to intercept the target). This is because the ground-based radars are distant from the target and the returned signal lacks resolution. However, it is still quite practical to use it to guide the missile to a location near the target, and then use another more accurate guidance method to actually intercept the target. Almost any type of terminal guidance can be used, but the most common are semi-active radar homing (SARH) or active radar homing.
Examples of missiles which use command guidance with terminal SARH include:
- Russian: SA-4 'Ganef', SA-6 'Gainful', SA-11 'Gadfly', SA-17 'Grizzly'
Examples of missiles which use command guidance with terminal active radar homing include:
- Russian: SA-5 'Gammon'
Track-via-missile is a variation of command guidance, the main difference being that the missile itself sends target tracking information back to the guidance system to aid it in calculating the intercept. This negates much of the accuracy disadvantage of pure command guidance.
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