Anti-radiation missile - AbsoluteAstronomy.com

An anti-radiation missile (ARM) is a missile

Missile

Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...

which is designed to detect and home on an enemy radio emission source. Typically these are designed for use against an enemy radar

Radar

Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

, although jammers and even radios used for communication can also be targeted in this manner.

Air-to-Ground

Most ARM designs to date have been intended for use against ground-based radars. Commonly carried by specialist aircraft in the SEAD

SEAD

Suppression of Enemy Air Defenses , also known as "Wild Weasel" and "Iron Hand" operations in the United States, are military actions to suppress enemy surface-based air defenses , primarily in the first hours of an attack.One fourth of American combat sorties in recent conflicts have been SEAD...

(Suppression of Enemy Air Defense) role (known to the USAF as "Wild Weasel

Wild Weasel

A Wild Weasel is an aircraft specially equipped with radar seeking missiles, and tasked with destroying the radars and SAM installations of enemy air defence systems....

s"), the primary purpose of this type of missile is to degrade enemy air defenses in the first period of a conflict in order to increase the chances of survival for the following waves of strike aircraft. They can also be used to quickly shut down unexpected SAM

Surface-to-air missile

A surface-to-air missile or ground-to-air missile is a missile designed to be launched from the ground to destroy aircraft or other missiles...

sites during a raid. Aircraft which fly with strike aircraft to protect them from enemy air defences often also carry cluster bombs and are known as a SEAD

SEAD

escort. The cluster bombs can be used to ensure that after the ARM disables the SAM system's radar, the command post, missile launchers, and other components or equipment are also destroyed to guarantee the SAM site stays down.

Early ARMs such as the AGM-45 Shrike

AGM-45 Shrike

AGM-45 Shrike is an American anti-radiation missile designed to home in on hostile antiaircraft radars. The Shrike was developed by the Naval Weapons Center at China Lake in 1963 by mating a seeker head to the rocket body of an AIM-7 Sparrow. It was phased out by U.S...

were not particularly intelligent; they would simply home in on the source of radiation and explode when they got near. SAM operators learned to turn their radar

Radar

off when an ARM was fired at them then turn it back on later, greatly reducing the missile's effectiveness. This led to the development of more advanced ARMs like the AGM-78 Standard ARM

AGM-78 Standard ARM

The AGM-78 Standard ARM was an anti-radiation missile developed by General Dynamics, United States of America.-Overview:Originally developed for the US Navy during the late 1960s, the AGM-78 was created in large part because of the limitations of the AGM-45 Shrike, which suffered from a small...

and AGM-88 HARM

AGM-88 HARM

The AGM-88 High-speed Anti-Radiation Missile is a tactical, air-to-surface missile designed to home in on electronic transmissions coming from surface-to-air radar systems. It was originally developed by Texas Instruments as a replacement for the AGM-45 Shrike and AGM-78 Standard ARM system...

missiles, which have inertial guidance systems (INS) built-in. This allows them to remember the radar's location if it is turned off and continue to home into it. It is less likely to hit the radar if it is turned off quickly, as the longer the radar is off (and assuming it never turns back on), the more error is introduced into the missile's course. However, the high speed and smokeless motors of the more recent missiles such as the HARM mean that they will probably close the distance significantly before anyone even realizes one has been fired. This gives the missile a much higher probability of destroying the radar even in this circumstance. In any case, even a temporary shut down of the enemy's missile guidance radar can be of a great advantage to friendly aircraft during battle.

Surface-to-Surface

Several surface-to-surface missile

Surface-to-surface missile

A surface-to-surface missile is a guided projectile launched from a hand-held, vehicle mounted, trailer mounted or fixed installation or from a ship. They are often powered by a rocket motor or sometimes fired by an explosive charge, since the launching platform is typically stationary or moving...

s, like the P-700 Granit

P-700 Granit

The P-700 Granit is a Soviet and Russian naval anti-ship cruise missile. Its GRAU designation is 3M45, its NATO reporting name SS-N-19 Shipwreck...

, P-500 Bazalt, MM40 Exocet

Exocet

The Exocet is a French-built anti-ship missile whose various versions can be launched from surface vessels, submarines, helicopters and fixed wing aircraft. Hundreds were fired in combat during the 1980s.-Etymology:...

and OTO Melara Teseo include a home-on-jam capability wherein the receiver component of their active radar seeker is used to home in on enemy radar, ECM or communications. This makes these missiles significantly harder to defeat with ECM and distraction countermeasures, and makes the use of semi-active

Semi-active radar homing

Semi-active radar homing, or 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 ...

missiles against them dangerous.

Surface-to-Air

Due to experiences with jamming during Vietnam and Middle Eastern wars in late 1960s by US-built aircraft, the Soviets have designed an alternative guidance mode for their S-75

S-75 Dvina

The S-75 Dvina is a Soviet-designed, high-altitude, command guided, surface-to-air missile system...

(SA-2) missiles, which allowed them to home onto the source of the jamming if normal forms of navigation failed. In cases of heavy jamming, missiles were often launched exclusively in this mode, ironically because passive tracking allowed the SAM operators to prevent American anti-radiation missiles from being fired at them in retaliation. Recently, The People's Republic of China developed the FT-2000 system to counter AEW and AWACS targets, based on the HQ-9 which is in turn based on the S-300PMU. The anti-radiation missile systems has been marketed to Pakistan and various countries, without success.

Air-to-Air

More recently, air-to-air ARM designs have begun to appear, notably the Russian Vympel R-27P. Such missiles have several advantages over other missile guidance

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...

techniques; they do not trigger radar warning receivers (conferring a measure of surprise), and they can have a longer range (since battery life of the seeker head is the limiting factor on the range of most active radar homing

Active radar homing

Active radar homing is a missile guidance method in which a guided missile contains a radar transceiver and the electronics necessary for it to find and track its target autonomously...

systems).

In the 1970s, Hughes Aerospace had a project called BRAZO (Spanish for ARM). Based on a Raytheon AIM-7 Sparrow, it was meant to offer an air-to-air capability against proposed Soviet AWACS types and also some other types with extremely powerful radar sets such as the MiG-25. The project was not proceeded with.

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