Active radar homing (ARH) is a missile guidance method in which a missile contains a radar transceiver (in contrast to semi-active radar homing, which uses only a receiver) and the electronics necessary for it to find and track its target autonomously. NATO brevity code for an air-to-air active radar homing missile launch is Fox Three.
There are two major advantages to active radar homing:
Because the missile is tracking the target, and the missile is typically going to be much closer to the target than the launching platform during the terminal phase, the tracking can be much more accurate and also have better resistance to ECM. Active radar homing missiles have some of the best kill probabilities, along with missiles employing track-via-missile guidance.
Because the missile is totally autonomous during the terminal phase, the launch platform does not need to have its radar enabled at all during this phase, and in the case of a mobile launching platform like an aircraft, can actually exit the scene or undertake other actions while the missile homes in on its target. This is often referred to as fire-and-forget capability and is a great advantage that modern air-to-air missiles have over their predecessors.
Many missiles employing this type of guidance have an extra trick up their sleeves; If the target does attempt to use noise jamming, they can in effect turn into an anti-radiation missile and home in on the target's radiation passively (home-on-jam). This makes such missiles practically immune to noise jamming.
Active radar homing is rarely employed as the only guidance method of a missile. It is most often used during the terminal phase of the engagement, mainly because since the radar transceiver has to be small enough to fit inside a missile and has to be powered from batteries, therefore having a relatively low ERP, its range is limited. To overcome this, most such missiles use a combination of command guidance with an inertial navigation system (INS) in order to fly from the launch point until the target is close enough to be detected and tracked by the missile. The missile therefore requires guidance updates via a datalink from the launching platform up until this point, in case the target is maneuvering, otherwise the missile may get to the projected interception point and find that the target is not there. Sometimes the launching platform (especially if it is an aircraft) may be in danger while continuing to guide the missile in this way until it 'goes active'; In this case it may turn around and leave it to luck that the target ends up in the projected "acquisition basket" when the missile goes active. It is possible for a system other than the launching platform to provide guidance to the missile before it switches its radar on; This may be other, similar fighter aircraft or perhaps an AWACS.
Most anti-ship missiles use active radar homing for terminal guidance.
Many ARH missiles with targets on land or sea use millimeter wave guidance.
Examples of missiles known to use active radar homing (all in their terminal phase) include:
DF-21
DF-25
DF-26
HN-2000
PL-12 air-to-air missile and SD-10 (export version to Pakistan)
PL-15 air-to-air missile
HQ-9 air defense missile
Meteor (missile) long-range air-to-air missile (With contribution from France, Germany, Italy, Spain, Sweden and United Kingdom)
MBDA Perseus (missile) (France, UK)
MBDA Exocet anti-ship missile
MICA (missile) air-to-air missile and surface-to-air missile
EADS AS.34 Kormoran anti-ship missile
DRDO-Astra BVRAAM
BrahMos
Prahaar (missile)
Arrow (Israeli missile)
Derby (missile)
Type 80 Air-to-Ship Missile
Type 81 Surface-to-air Missile (SAM-1C only)
Type 88 Surface-to-Ship Missile
Type 90 Ship-to-Ship Missile
Type 91 Air-to-Ship Missile
Type 99 air-to-air missile (Mitsubishi AAM-4, AAM-4Kai)
Type 03 Medium-Range Surface-to-Air Missile
Type 11 Surface-to-air Missile
NPO Novator and DRDO R-172 long range air-to-air missile
Vympel NPO R-37 (AA-13 Arrow) long range air-to-air missile
Vympel NPO R-33 (AA-9 Amos) long range air-to-air missile
Vympel NPO R-77 (AA-12 Adder) medium range air-to-air missile
Tactical Missiles Corporation Kh-31 (AS-17 Krypton) anti-shipping missile (Kh-31A only)
Raduga Kh-15 (AS-16 Kickback) air-to-surface missile (Kh-15S only)
Raduga Kh-59 (AS-13 Kingbolt) air-to-surface missile (Kh-59MK only)
Tactical Missiles Corporation Kh-25 (AS-10 Karen) air-to-surface missile (Kh-25MA only)
Raduga KSR-5 (AS-6 Kingfish) anti-shipping missile
Raduga KSR-2 (AS-5 Kelt) anti-shipping missile
Raduga Kh-22 (AS-4 Kitchen) anti-shipping missile
KBM Khrizantema (AT-15 Springer) anti-tank missile (9M123-2 and 9M123F-2 variants only)
NPO Mashinostroyeniya P-500 Bazalt (SS-N-12 Sandbox) anti-ship missile
NPO Mashinostroyeniya P-700 Granit (SS-N-19 Shipwreck) anti-ship missile
Raduga P-270 Moskit (SS-N-22 Sunburn) anti-ship missile
Tactical Missiles Corporation Kh-35 (SS-N-25 Switchblade) anti-ship missile
NPO Mashinostroyeniya P-800 Oniks (SS-N-26) anti-ship missile
NPO Novator 3M-54 Klub (SS-N-27 Sizzler) anti-ship missile
R-Darter
Saab Bofors Dynamics RBS-15 anti-ship missile
Sky Sword II air-to-air missile
Hsiung Feng I
Hsiung Feng II
Hsiung Feng IIE
Hsiung Feng III
Boeing Harpoon anti-ship missile
Hughes Aircraft Company AIM-47 Falcon
Lockheed Martin AGM-114L Hellfire Longbow air-to-surface missile
Lockheed Martin MIM-104 Patriot surface-to-air missile (PAC-3 version only)
Martin Marietta Pershing II (topographic radar version of DSMAC)
Raytheon AIM-54 Phoenix long range air-to-air missile
Raytheon AIM-120 AMRAAM air-to-air missile and surface-to-air missile
Raytheon GBU-53/B
Raytheon RIM-174 Standard ERAM (Standard Missile 6) surface-to-air missile
Raytheon AGM-88 HARM (only E version)
The U.S. Navy's Bat radar-guided glide bomb of World War II, world's earliest munition design known to use an active radar homing system.
