The AGM-88 High-speed Anti-Radiation Missile (HARM) 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. Production was later taken over by Raytheon Corporation when it purchased the defense production business of Texas Instruments.
The AGM-88 can detect, attack and destroy a radar antenna or transmitter with minimal aircrew input.
The proportional guidance system that homes in on enemy radar emissions has a fixed antenna and seeker head in the missile's nose. A smokeless, solid-propellant, booster-sustainer rocket motor propels the missile at speeds over Mach 2. HARM, a U.S. Navy-led program, was initially integrated onto the A-6E, A-7 and F/A-18 and later onto the EA-6B. RDT&E for use on the F-14 was begun, but not completed. The USAF introduced HARM on the F-4G Wild Weasel and later on specialized F-16s equipped with the HARM Targeting System (HTS).
Development
Because of the less than satisfactory performance of the AGM-45 Shrike and AGM-78 Standard ARM in Vietnam, the Naval Weapons Center started a program in 1969 to develop a new anti-radiation missile. A major development goal was a high-speed missile (because this gave enemy radar operators less time to shut down their emitters), and therefore the project was named HARM (High-Speed Anti-Radiation Missile). Other goals included broadband seekers, a large warhead, operational flexibility, and high reliability. In 1970, the designation ZAGM-88A was allocated to the projected missile.
Because of the ambitiuos specifications, development was slow. In 1974, Texas Instruments was announced as prime contractor for the HARM, and the first flight of an AGM-88A missile occurred in 1975. Various problems were encountered in the development of the seeker and guidance system, including inability to distinguish between emissions from behind and in front of the aircraft. In early 1980, the problems were essentially solved, and in 1981, the initial production contract was awarded to Texas Instruments. The first production AGM-88A missiles were delivered in 1983, and HARM reached IOC (Initial Operational Capability) with the U.S. Navy in 1985, and the USAF in 1987. The first operational use of HARM occurred in April 1986, when the type was used to destroy Libyan radars.
AGM-88 design
The AGM-88A HARM used a broadband spiral antenna, a software programmable seeker which was conceptually similar in design to an RWR, providing coverage from the C through to the J band (2-20 GHz). The missile used a steel cube blast fragmentation warhead, and a low smoke rocket motor. It was faster and longer ranging than the Shrike and Standard.
The big innovation in the HARM was in its intelligent (radar) video processor based seeker, which was designed to recognise the characteristic Pulse Repetition Frequencies (PRF) of threat radars, in a manner similar to that performed by an RWR. This would allow the missile to select a specific radar operating in any given band. Indeed, the HARM offered higher sensitivity and frequency coverage than many earlier RWRs in US service, and aircraft carrying the HARM often used it to supplement the RWR.
Because a programmable video processor was used, decision logic in the missile's software allowed it to select the highest threat target should the emitter it was fired at shut down. The use of an inertial midcourse guidance package allowed long range shots against emitters which could be difficult to home on at such ranges, once close enough the HARM would switch to its receiver and home to impact.
Variant
The AGM-88A
The AGM-88A missile is powered by a Thikol SR113-TC-1 dual-thrust (boost/sustain) low-smoke solid-fueled rocket motor, and has a 66 kg (146 lb) WDU-21/B blast-fragmentation warhead (25000 steel fragments) in a WAU-7/B warhead section. The warhead is triggered by an FMU-111/B laser proximity fuze. The seeker of the WGU-2/B guidance section has to be pre-tuned to likely threats at depot-level maintenance, so every base or ship has to store a selection of differently tuned HARM seeker heads. In flight, the AGM-88 is controlled by the WCU-2/B control section using four movable BSU-59/B mid-body fins, and stabilized by the fixed BSU-60/B tailfins.
The AGM-88A Block II
This variant had a new seeker with software in an EEPROM, which could be reprogrammed for new types of threats at short notice.
The AGM-88B
This variant had the Block II seeker from the beginning, but had improved computer hardware in its WGU-2B/B guidance section, compatible with the forthcoming Block III software.
The AGM-88b Blok III
Available from 1990, improved the in-flight reprogramming (a.k.a. flexing) capabilities of the AGM-88B, as well as the PB mode targeting capabilities. The AGM-88B Block III was very widely and successfully used in the 1991 Gulf War, with more than 2000 HARMs fired at Iraqi radars. However, because the Block III update required fully powering up the missile, the U.S. Navy decided to retain its Block II missiles on aircraft carriers for safety reasons (powering up live missiles in the shops below deck was considered too risky). The ATM-88B, CATM-88B, and DATM-88B are the training variants of the AGM-88B, equivalent to the corresponding -88A versions.
The AGM-88C
The major hardware improvement was a new WDU-37/B warhead with 12800 tungsten alloy fragments and a revised explosive charge, which significantly enhanced the lethality of the missile. The AGM-88C was initially produced with Block IV software in the upgraded WGU-2C/B guidance section. The WGU-2C/B used a single antenna instead of the previous two, and has a much more powerful signal processor. Block IV software was updated to counter the latest threats, and increased TOO mode capability by doubling the seeker range sensitivity. All AGM-88C production missiles were built by Texas Instruments as AGM-88C-1. The AGM-88C-2 by Loral, with an alternative low-cost seeker, was test-flown, but not produced in quantity. There are also ATM-88C and CATM-88C training variants of the AGM-88C (but apparently no DATM-88C).
The next upgrade was a software update only, called Block V when applied to the AGM-88C Block IV, and Block IIIA, when applied to the older AGM-88B Block III. This update introduced home-on-jam capability, including the option to home on jammers which try to disrupt the ever more important GPS navigation system (used by many of the latest guided weapons). The U.S. Navy began to upgrade its HARMs to Block IIIA/V standard in early 2000. Block IIIA/V also allows the AGM-88B/C to be safely reprogrammed at sea.
The AGM-88D
This upgrade effort for HARM is known as Block VI, an international collaboration by the U.S. (Raytheon), Germany (BGT), and Italy (Alenia). The main improvement of HARM Block VI is the incorporation of a GPS navigation system. This greatly increases accuracy when radar lock is lost after emitter switch-off, because the GPS guidance keeps the missile within a narrow box towards the last known emitter position. This is especially desirable in wars, where enemy radar installations are deliberately placed near sensitive civilian areas, like schools or hospitals. This often prevented the use of earlier HARM missiles in the Kosovo campaign, because a deviation after radar loss could lead to unacceptable collateral damage. Using GPS guidance as a primary means of homing on the target, Block VI HARMs could even be used as general purpose high-speed precision ground attack missiles.
The AGM-88D was in the EMD phase in 2002, and IOC at that time was planned for 2003. However, as of 2005, no AGM-88Ds were listed in the Navy's inventory, and it therefore appears that either the procurement of Block VI upgrade kits has been cancelled or the upgraded missiles are still referred to as AGM-88B/C.
The AGM-88E AARGM (Advanced Anti-Radiation Guided Missile)
The AARGM is a further improved Block VI missile, which uses not only the AGM-88D's GPS but also an MMV (Millimeter Wave) active radar seeker for terminal homing in its new WGU-48/B guidance section. The MMW seeker will employ active target recognition algorithms, and therefore be able to strike not only the radar emitter, but also e.g. the control vehicle of the site. The program started at the NWC (Naval Weapons Center) China Lake in 1998, and in March 2000, the first test firing of the MMW seeker in a modified HARM was successful. AARGM development continued with modified AGM-88 missiles, and an SD&D (System Development & Design) contract for the production AARGM was awarded to ATK (Alliant Techsystems Inc.) in June 2003. The first AGM-88E flight test of the DT (Developmental Testing) phase occured in May 2007. At that time, LRIP (Low Rate Initial Production) was expected to begin in 2008, and initial fielding in 2009. The CATM-88E is the captive-carry training variant, while the DATM-88E is the inert ground-handling trainer. A long term goal of the AARGM program is the development of an entirely new stealthy airframe, compatible with the internal weapon bays of the F-22 and Joint Strike Fighter.
Primary Function: Air-to-surface anti-radiation missile
Mission Defense suppression
Targets Fixed soft
Service US Navy and Air Force
Contractor: Raytheon [Texas Instruments]
Program status Operational
Date Deployed: 1984
Power Plant: Thiokol SR113-TC-1 dual-thrust rocket motor
Thrust: Dual thrust
Length: 13 feet, 8 inches (4.14 meters)
Launch Weight: 800 pounds (360 kilograms)
Diameter: 10 inches (25.40 centimeters)
Wingspan: 3 feet, 8 inches (101.60 centimeters)
Range: 150 km (80 nm)
Speed: Max. speed: 2280 km/h (1,420 mph)
Guidance System: Passive radar homing with home-on-jam, GPS/INS and millimeter wave active radar homing in E variant. 500-20,000 MHz for AGM-88C
Guidance method Homes on electronic emissions
Warhead WAU-7/B, 143.51bs. Direct Fragmentation
Explosive (NEW) PBXC-116 (45.2 lbs.)
Fuze Pulsed Laser Proximity/Contact
Propulsion Boost Sustain 64,000 lbs./sec. Low Smoke
Development cost $644.5 million
Production cost $5,568.1 million
Total acquisition cost $6,212.6 million
Acquisition unit cost $316,856
Production unit cost $283,985
Quantity 19,607 (Navy and Air Force)
Platforms F/A-18, F-4G, F-16