Missile Guidance Systems

inertial guidance system

The inertial guidance system is an electronic system consisting of gyroscopes,
accelerometers, and a computer that starts with an initial reference point,
and continuously monitors the position, velocity, and acceleration of a
missile, and thus provides navigational data or control without
the need for communicating with a base station.

astro-inertial guidance system

The astro-inertial guidance system uses star positioning to fine-tune
the accuracy of the inertial guidance system after launch. As the
accuracy of a missile is dependent upon the guidance system
knowing the exact position of the missile at any given moment during its
flight, the fact that stars are a fixed reference point from which to calculate
that position makes this a potentially very effective means of improving
accuracy.

active radar homing (ARH)

Active radar homing (ARH) is a missile guidance system in which a missile contains
a radar transceiver, and the electronics necessary for it to find and track its target
autonomously.

semi-active radar homing (SARH)

Semi-active radar homing (SARH) is a common type of missile guidance system,
perhaps the most common type for longer-range air-to-air and surface-to-air missile
systems. The name refers to the fact that the missile itself is only a passive detector
of a radar signal, provided by an external ("offboard") source, as it reflects off the
target. Semi-active missile systems use bistatic continuous-wave radar as the
"offboard" radar source.

infrared homing

Infrared homing is a passive missile guidance system which uses the infrared (IR) light
emission from a target to track and follow it. Missiles which use infrared seeking are
often referred to as "heat-seekers" since infrared is radiated strongly by hot bodies.
Many objects such as people, vehicle engines and aircraft generate and emit heat,
and so are especially visible in the infrared wavelengths of light compared to objects
in the background.

Missile Guidance Special Notes

A missile will typically use many guidance methods during its time of flight. During the
initial boost phase and up to the mid course phase, many missiles use inertial guidance.
At that point, the target tracking radar will send mid course correction information to the
missile via a tracking radar uplink, and the missile will continue on a corrected course
toward its target. Then during the terminal phase of flight, the missile will switch to one
of the following guidance modes:

* active radar homing (ARH)
* semi-active radar homing (SARH)
* ifrared homing (passive)

If the missile is in the presence of significant noise jamming in the terminal phase of flight,
it may switch to passive missile guidance, and home in on the jamming source.