F218 Mecklenburg-Vorpommern Radarantenne

Lock-on is a feature of many

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

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

In the post-WWII era, the term became more widely used in connection to

missile guidance Missile guidance refers to a variety of methods of guiding a missile or a guided bomb to its intended target. The missile's target accuracy is a critical factor for its effectiveness. Guidance systems improve missile accuracy by improving its P ...

concepts. Many modern anti-aircraft missiles use some form of

semi-active radar homing 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 dete ...

, 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 missile A surface-to-air missile (SAM), also known as a ground-to-air missile (GTAM) or surface-to-air guided weapon (SAGW), is a missile designed to be launched from the ground or the sea to destroy aircraft or other missiles. It is one type of anti-ai ...

s 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 A radar system uses a radio-frequency electromagnetic signal reflected from a target to determine information about that target. In any radar system, the signal transmitted and received will exhibit many of the characteristics described below. ...

, often by increasing the

pulse repetition frequency The pulse-repetition frequency (PRF) is the number of pulses of a repeating signal in a specific time unit. The term is used within a number of technical disciplines, notably radar. In radar, a radio signal of a particular carrier frequency is tu ...

. This led to the introduction of

radar warning receiver Radar warning receiver (RWR) systems detect the radio emissions of radar systems. Their primary purpose is to issue a warning when a radar signal that might be a threat is detected, like a fighter aircraft's fire control radar. The warning can ...

s that would notice this change and provide a warning to the operator. Modern radar systems do not have a lock-on system in the traditional sense; tracking is provided by storing radar signals in

computer memory Computer memory stores information, such as data and programs, for immediate use in the computer. The term ''memory'' is often synonymous with the terms ''RAM,'' ''main memory,'' or ''primary storage.'' Archaic synonyms for main memory include ...

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

With a

system, the launch platform acquires the target with its search

. 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 Passive radar (also referred to as parasitic radar, passive coherent location, passive surveillance, and passive covert radar) is a class of radar systems that detect and track objects by processing reflections from non-cooperative sources of illu ...

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.

Detection by the target

The 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.

Notes

{{reflist Aerial warfare strategy Air-to-air missiles Surface-to-air missiles Military radars

History

Types

Detection by the target

See also

Notes