HARM Credit - via Andreas Parsch

Historical Essay © Andreas Parsch

Raytheon (Texas Instruments) AGM-88 HARM

The AGM-88 HARM (High-Speed Anti-Radiation Missile) is currently the standard U.S. anti-radiation missile, and also widely used by other countries. It has completely replaced the earlier AGM-45 Shrike and AGM-78 Standard ARMs.

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.

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 HARM can be used in three different operational modes, known as Pre-Briefed (PB), Target Of Opportunity (TOO), and Self-Protect (SP). In PB mode, the long range (up to 150 km (80 nm)) of the AGM-88 is used to launch the missile on a lofted trajectory toward a known threat. When the HARM reaches lock-on range, and detects the radar emission, it can home on the target. If the target radar has been switched off before any lock could be acquired, the missile destroys itself to avoid possible friendly casualties by the impact of the now unguided missile. In SP mode, the aircraft's radar warning receiver is used to detect enemy emissions. The CP-1001B/AWG HARM Command Launch Computer (CLC) then decides which target to attack, transmits the data to the missile, and launches the AGM-88. TOO mode means that the seeker of the AGM-88 itself has detected a target, and the missile can be fired manually if the radar emission is identified as a threat. In SP and TOO modes, the AGM-88 can even be fired at targets behind the launching aicraft, although this of course significantly reduces the missile's range. The AGM-88 missile has an inbuilt inertial system, so that whenever it has acquired a lock once, it will continue towards the target even if the emitter is shut down (although the CEP is larger in this case).

The ATM-88A is a training version with an inert WAU-11/B warhead section, the CATM-88A is used for captive (non-launching) flight training, and the DATM-88A is used for loading and handling training.

The original AGM-88A missiles were also classed as Block I. The AGM-88A Block II, introduced in 1986, had a new seeker with software in an EEPROM, which could be reprogrammed for new types of threats at short notice. In 1987, the production switched to 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. This Block III update, 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 next upgrade of the HARM produced the AGM-88C, which became operational in 1993. 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 current 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 will be the incorporation of a GPS navigation system. This will greatly increase 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. AGM-88Cs upgraded to Block VI standard will be known as AGM-88D in U.S. service. Germany and Italy, which mainly have older AGM-88Bs in stock, will refer to their upgraded missiles as AGM-88B Block IIIB. The AGM-88D is currently in the EMD phase, and IOC is planned for 2003.

A more advanced HARM update program is known as 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 continues with modified AGM-88 missiles, and contract award for the SD&D (System Development & Demonstration) phase is planned for late 2002. Developmental testing of the AGM-88E is scheduled for 2005, with a planned Initial Operational Capability in 2008. The CATM-88E will be the captive-carry training variant. 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.

Currently, the primary U.S. carrier aircraft for the AGM-88 are the USAF's F-16C Block 50 (equipped with the AN/ASQ-213 HARM Targeting System) and the USN's EA-6B. The main launcher for the AGM-88 is the LAU-118/A. More than 21000 AGM-88 missiles of all variants have been built so far. Current production is limited to new guidance sections and warheads, to allow the upgrade of older AGM-88A rounds to the latest standards.

Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for AGM-88A (except where noted):

[1] Anthony Thornborough: "Iron Hand", Sutton Publishing, 2001
[2] Norman Friedman: "US Naval Weapons", Conway Maritime Press, 1983
[3] Norman Friedman: "World Naval Weapons Systems, 1997/98", Naval Institute Press, 1997
[4] Bill Gunston: "The Illustrated Encyclopedia of Rockets and Missiles", Salamander Books Ltd, 1979
[5] Hajime Ozu: "Missile 2000 - Reference Guide to World Missile Systems", Shinkigensha, 2000
[6] Bernard Blake (ed.): "Jane's Weapon Systems 1987-88", Jane's, 1988
[7] "Navy Training System Plan for the AGM-88 HARM and AARGM Systems", U.S. Navy, 2002

Manufacturer: NWC/Texas Instruments.

High velocity anti-radiation missile.

Manufacturer: NWC/Texas Instruments. Total Mass: 351 kg (773 lb). Core Diameter: 0.24 m (0.78 ft). Total Length: 3.96 m (12.99 ft). Span: 1.13 m (3.70 ft). Standard warhead mass: 66 kg (145 lb). Maximum range: 19 km (11 mi). Boost Propulsion: Solid rocket. Guidance: Radar Homing. Maximum speed: 2,480 kph (1,540 mph). Development Cost $: 346.900 million. in: 1982 average dollars. Recurring Price $: 0.285 million. Total Number Built: 21488. Flyaway Unit Cost $: 0.287 million. in: 1982 unit dollars.

High velocity anti-radiation missile.

Manufacturer: Raytheon Co., Raytheon Systems Co. Location: Lewisville, TX, USA. Guidance contractor: Raytheon. Total Mass: 363 kg (800 lb). Core Diameter: 0.25 m (0.83 ft). Total Length: 4.18 m (13.70 ft). Span: 1.13 m (3.70 ft). Standard warhead mass: 66 kg (145 lb). Maximum range: 25 km (15 mi). Boost Propulsion: Solid rocket. Boost engine: YSR113-TC-1. Guidance: Radar homing.

Manufacturer: Texas Instruments.