Anti-radiation missile 1032936 221120009 2008-06-23T03:31:59Z 76.121.217.52 /* Air-to-Air */ [[Image:AGM-88 HARM on FA-18C.jpg|thumb|HARM on a US Navy F-18C]] [[Image:ALARM.jpeg|thumb|ALARM under the wing of a Tornado.]] An '''anti-radiation missile''' (ARM) is a [[missile]] which is designed to detect and home in on an enemy radio emission source. Typically these are designed for use against an enemy [[radar]], 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]] (Suppression of Enemy Air Defense) role (known to the [[USAF]] as "[[Wild Weasel]]s"), the primary purpose of this type of missile is to degrade enemy air defences 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 [[Surface-to-air missile|SAM]] 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]] 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]] were not particularly intelligent; they would simply home in on the source of radiation and explode when they got near. Smart SAM operators learned to turn their [[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]] and [[AGM-88 HARM]] missiles, which have [[inertial guidance system]]s (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 [[AGM-88 HARM|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. The British [[ALARM]] has the ability to loiter: a parachute allows it to slow its descent until the radar reactivates. The [[AGM-136 Tacit Rainbow]] (an American missile) would have operated in the same way. This was a small, air launched cruise missile, which could be fired either at a transmitting radar, or an area in which SAM radars are believed to be hiding. In the event of the radar deactivating, the Tacit Rainbow would loiter, using its small jet engine, until the radar reappeared – a ''Persistent'' Anti-radiation Missile. The project was cancelled in 1991, for budget reasons. Another design point of modern ARM missiles, other than the range (which is hopefully greater than that of the SAM systems it will be targeted at), is their speed. Some SAM systems utilize huge missiles which are able to accelerate up to incredible speeds (some as high as [[Mach (speed)|Mach]] 6), which means that if the ARM is to be useful in a "duel" between an aircraft and a SAM site, the ARM should be able to fly to and hit the SAM site faster than the SAM can fly to and hit the aircraft. The [[AGM-88 HARM]] mostly succeeds in this area; its top speed of around [[Mach (speed)|Mach]] 4 is partly due to its altitude and speed advantage at launch over the SAM (which has to climb from rest at ground level), and partly due to its powerful rocket motor. This means that if the SAM launches a missile at the aircraft first, unless it is one of the fastest SAM systems such as the [[SA-10 Grumble|SA-10]]/[[SA-10 Grumble|S-300]] or [[S-400|SA-20/S-400]], the aircraft is likely to win. == Surface-to-Surface == Several [[surface-to-surface missile]]s, like the [[P-700 Granit]], [[P-500 Bazalt]], [[Exocet|MM40 Exocet]] 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 radar homing|semi-active]] 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]] (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-27|Vympel R-27P]]. Such missiles have several advantages over other [[missile guidance]] 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]] systems). The American-made [[AIM-120 AMRAAM]] air-to-air missile seeks out electronic jamming countermeasures to improve end-stage performance, its so-called "home on jam" capability. However, this anti-radiation mode is not the exclusive means of guidance of the unit. == References == {{cite news |author = Reuben Johnson |url = http://www.ainonline.com/Publications/asian/asian_06/d3improved10.htm |title = Improved Russian radar may level playing field |publisher = Asian Aerospace |date = 2006-02 |accessdate = 2006-07-10 }} http://www.pakdef.info/pakmilitary/army/sam/sa2guideline.html http://pvo.guns.ru/s75/s75_combat.htm (in Russian) {{Missile types}} [[Category:Anti-radiation missiles]] [[it:Missile antiradar]] [[he:טיל נגד קרינה]] [[ja:対レーダーミサイル]] [[pl:Pocisk przeciwradarowy]] [[fi:Tutkaan hakeutuva ohjus]] [[zh:反輻射飛彈]]