Lock-on is a feature of many radar systems that allow it to automatically follow a selected _target. Lock-on was first designed for the AI Mk. IX radar in the UK, where it was known as lock-follow or auto-follow. Its first operational use was in the US ground-based SCR-584 radar, which demonstrated the ability to easily track almost any airborne _target, from aircraft to artillery shells.
History
editIn the post-WWII era, the term became more widely used in connection to missile guidance concepts. Many modern anti-aircraft missiles use some form of semi-active radar homing, where the missile seeker listens for reflections of the launch platform's main radar. To provide a continuous signal, the radar is locked-onto the _target, following it throughout the missile's flight. Ships and surface-to-air missiles often have a dedicated illuminator radar for this purpose.
In older radar systems, through the 1980s, lock-on was normally assisted by a change in the radar signal characteristics, often by increasing the pulse repetition frequency. This led to the introduction of radar warning receivers that would notice this change and provide a warning to the operator.[1]
Modern radar systems do not have a lock-on system in the traditional sense; tracking is provided by storing radar signals in computer memory and comparing them from scan to scan using algorithms to determine which signals correspond to single _targets. These systems do not change their signals while tracking _targets, and thus do not reveal they are locked-on.
Types
editWith a semi-active radar homing system, the launch platform acquires the _target with its search radar. The missile is then powered up while the launch platform's illuminator radar "lights up" the _target for it. The illuminator is a radar transmitter with a narrow, focused beam that may be separate from the search radar and that can be directed at a _target using information from the search radar. When the passive radar of the missile's guidance system is able to "see"/detect the radio waves reflected from the _target, missile lock-on is achieved and the weapon is ready to be launched.[2]
Detection by the _target
editThe subject of a radar lock-on may become aware of the fact that it is being actively _targeted by virtue of the electro-magnetic emissions of the tracking system, notably the illuminator. This condition will present a heightened threat to the _target, as it indicates that a missile may be about to be fired at it.
See also
editNotes
edit- ^ R. P. G. Collinson (2003). Introduction to Avionics Systems. Springer. ISBN 1-4020-7278-3.
- ^ Carlo Kopp (June 1982). "Active and Semi-Active Radar Missile Guidance". Australian Aviation.