Whither the Weasel?

Shown here on the outboard wing pylon of a USN VAQ-131 EA-18G Growler, AGM-88 HARM variants have been supplied to 11 air forces around the world together with the USN and the US Marine Corps. (USAF)

The real threat from ground based surface-to-air missiles means that there is still a need to keep the Vietnam ‘Wild Weasel’ capability current.

The US Navy’s (USN) announcement that the Northrop Grumman AGM-88E Advanced Anti-Radiation Guided Missile – Extended Range (AARGM-ER) had received Milestone C programme approval on 23 August 2021 focused attention on the role and utility of anti-radiation missiles (ARM) in 21st Century warfare.

Historically, ARM technology emerged during the Southeast Asian conflicts of the 1960s/70s when an urgent need arose for an effective counter to radar guided surface-to-air missiles (SAM). Accordingly, the US Air Force (USAF) and the US Navy (USN) fielded the Naval Weapons Centre AGM-45 Shrike weapon which incorporated a passive radar seeker to home-in on the radars associated with North Vietnamese SA-2 SAMs. While potentially effective, Shrike had the singular disadvantage of going ballistic if the signal being homed on went off air. To counter this, the General Dynamics AGM-78 Standard ARM was introduced which brought to the table the ability to remember the location of a shut-down emitter. Moving forward, SAM technology improved and proliferated to the point where a much faster and flexible ARM was required, a situation that resulted in America’s third generation AGM-88 High-Speed ARM (HARM) which remains in widescale service at the time of writing.

US Air Force McDonnell Douglas EF-4C Phantom II
A US Air Force McDonnell Douglas EF-4C Phantom II over North Vietnam in December 1972. It is armed with AGM-45 Shrike and AIM-7 Sparrow missiles and carries an AN/ALQ-72 ECM pod. (US Air Force)

While effective, baseline HARM has to an extent been overtaken by SAM technology and as of 2021, was expected to be replaced in US and other services by the AGM-88E configuration which adds an active terminal guidance seeker to the earlier models passive receiver in order to maximise effectiveness. The AARGM-ER variant is, as its designation indicates, an extended range configuration of AARGM that in the words of the USN, improves the baseline AARGM capability to include “extended range, survivability and effectiveness against future threats”. Perhaps more importantly, AARGM-ER is compatible with the Lockheed Martin F-35 Lightning II.

AARGM-ER completed its first live fire event on 19 July 2021 off the coast of the Point Mugu Sea Test Range in California, USA. (USN)

While the US (and at least four other countries) continue to use and develop ARM technology which is an obvious endorsement of the capability, it should be remembered that the combination of battle space connectivity, ‘smart’ weaponry and lethal drones, offer effective alternatives to the ARM in the counter-SAM role.

Equally, the range and speed of ‘high-end’ SAMs creates a fine balance between the ARM hitting its target before the SAM itself hits. Again, the argument continues as to whether or not it is better to destroy a SAM site rather than to drive it off-air and/or disable its radar antenna/s and wound its operating crew. These latter points are significant in that it is probably easier to replace a SAM system than to expend time and energy on attempting to repair a damaged system and/or tend to its wounded crew members. A final point regarding the continuing utility of ARMs is their ability to be rather effective strike weapons with, for example, a HARM round being quite capable of severely damaging, if not sinking, a warship onto whose radars it has homed.

As already noted, ARM technology is not the sole prerogative of the US, with manufacturers in Brazil, India, the People’s Republic of China (PRC) and the Russian Federation all producing ARMs in addition to the AGM-88 series developed by the Americans. To these, the British Air-Launched Anti-Radiation Missile (ALARM) should be perhaps added as although withdrawn from Royal Air Force (RAF) service during 2013, the weapon may remain in the Royal Saudi Air Force’s (RSAF) inventory. Saudi ALARMs are known to have been re-qualified during late 2012 and to have been used operationally against targets in Yemen during 2015.

Returning to the given list of ARM producers, development of Brazil’s MAR-1 ARM is understood to have begun during the late 1990s, with captive flight trials following a decade later. A product of a consortium made up of the then Mectron and the Brazilian Air Force’s Aerospace Technology and Science Department, MAR-1 is believed to be a 586lb (266kg) weapon that is 12.7ft (3.9m) long; incorporates a 200lb (90kg) warhead, a locally produced passive radar seeker, a laser/impact fusing and a rocket motor and which has a range of between 60-100km (37-62 miles). Operating modes are thought to comprise reactive and pre-programmed and the type is known to have been test fired from Brazilian AMX (A-1M) strike aircraft and to have been supplied to Pakistan where it has been integrated with that country’s Dassault Mirage V and Pakistan Aeronautical Complex (PAC) and the Chengdu Aircraft Corporation (CAC) JF-17 fast jets. At the time of writing, Brazil’s Embraer A-1M aircraft have been quoted as being slated to remain in service until the early 2030s.

Indias NGARM

Intended to be an equivalent of the American AARGM capability, India’s 18ft (5.5m) long Rudram1 next generation ARM (NGARM) has been designed by the country’s Defence Research and Development Organisation (DRDO) and is slated for production by various divisions of national contractor Bharat. Weighing in at 1,322lb (600kg), the weapon is billed as featuring a locally developed passive radar seeker/millimetre-wave terminal guidance homing head, as being fitted with a fragmentation warhead with a proximity fuze, as being powered by a solid-fuel rocket motor and as having a range of up to 200km (1,243 miles). Again, the missile is designed to be compatible with the SEPECAT Jaguar, Mikoyan MiG-29, Mirage 2000, Hindustan Aeronautics Tejas and Sukhoi Su-30MKI types. According to local news reports, Rudram 1 development began during 2012, with captive flight trials taking place during 2016. Follow-on flight trials are said to have been undertaken during 2018, with a 2019 test shot being said to have hit its designated target with a “high degree of accuracy”. The cited media sources further suggest that the Indian Air Force (IAF) would like to introduce Rudram 1 into service circa 2022, with (at the time of writing) the DRDO working on improved software for the missile together with a ground-launched variant.

For its part, the PRC’s YJ-91 ARM variant (there is also an anti-shipping configuration) is understood to be a development of the Russian Kh-31P that features, in the first instance, field-changeable passive seekers tuned to particular target frequencies. As such, the missile is produced by the Hongdu Aviation Industry Corporation, is 15.4ft (4.7m) long, is equipped with a 364lb (165kg) warhead and is quoted as having a maximum range of 120km (74 miles). Thought to have entered service circa the late 1990s, European media sources indicate that one of its latest applications is aboard the People’s Liberation Army Navy Air Force’s Shenyang J-15 aircraft. Again, it is further suggested that the Chinese are in the throes of developing a wideband, multi-frequency homer that will replace the baseline YS-91’s interchangeable seeker configuration.

Within the Russian Federation, ARM production is vested in the country’s Tactical Missile Corporation (TMC) whose September 2021 portfolio included the Kh-31P, Kh-31PD, Kh-31PK, Kh-58E and Kh-58UShKE. In order, the 1,322lb (600kg) – launch weight – Kh-31P is equipped with interchangeable, frequency specific homing heads (designated as the L-111, -112 and -113) and an 191lb (87kg) warhead. Again, it is 17ft (4.7m) long, has a 3,281 to 49,215ft (1,000 to 15,000m) launch envelope, has a range of up to 110km (68 miles) and has a target set that includes the American AN/MPQ-53 and AN/SPY-1 radars. Aircraft that are compatible with Kh-31P include the MiG-29, Su-25, Su-27, Su-30 and Su-34 types and the missile can be used with the L-080 Fantasmagoria-A and L-081 Fantasmagoria-B emitter location systems. For its part, the Kh-31PD configuration is designed for use against SAM-related radars, is 17ft (5.3m) long, has a maximum launch weight of 1,576lb (715kg), utilises a ‘universal cluster’ warhead, has a range of up to 250km (155 miles) with high-altitude launch, is equipped with a wideband passive seeker and is compatible with the MiG-29, MiG-35, Su-35 and Su-35MK (including the MKI, MKM and MK2 sub-variants) types.

On USAF F-16CJ/DJ aircraft, HARM is teamed with the AN/ASQ-213 emitter location system which allows them to make use of the missile’s ‘range-known’ operating mode (USAF)

The remaining member of the Kh-31P family (the Kh-31PK) is a -31P variant that is equipped with a proximity fuse, an ‘increased efficiency’ payload, interchangeable frequency-specific seeker heads and is optimised for use against medium- and long-range air defence radar emitters. In more detail, the weapon is 15.4ft (4.8m) long, has a launch weight of 1,333lb (605kg) (± 10kg), has a maximum range of 110km (68 miles) and has a launch envelope of between 328 to 49,215ft (100 to 15,000m).

Beyond the Kh-31 series, the TMC ARM portfolio also includes the Raduga developed/manufactured Ku-58 family which includes the baseline Kh-58E (the ‘E’ indicating export configuration) and the Kh-58UShKE configurations. For its part, the 1,433lb (650kg) (launch weight) Kh-58E missile is 15.4ft (4.8m) long, incorporates a 328lb (149kg) warhead, has a maximum range of 200km (124 mile) high-altitude launch, a launch envelope of between 656 to 65,620ft (200 to 20,000m) and is equipped with a three band homing head which includes in its target set the American AN/TPS-43, -44 and -53 radars. Aircraft types compatible with the Kh-58E include the Su-24MK and Su-25TK types. Although included in the Kh-58 family, the 1,433lb (650kg) (launch weight), export orientated Kh-58UShKE is a somewhat different weapon in that it is suitable for both external and internal carriage, features folding fins for the latter option, has a maximum range of 245km (145 miles), is fitted with a 328lb (149kg) warhead and utilises a seeker head that covers pulsed (1.2 to 11GHz frequency band) and continuous wave emitters.

Of these various Russian-sourced weapons (and over time), Kh-31P missiles have been supplied to the air forces of Russia (Su-24 only), China, India and Syria, while Kh-58 series munitions have been sold to Azerbaijan, Belarus, Bulgaria, the Czech and Slovak Republics, Georgia, Iran, Kazakhstan, North Korea, the Ukraine and Uzbekistan. How many such weapons remain in service (and with whom) is a matter for conjecture.

Turning to ongoing US activity, an AGM-88 HARM development contract was awarded during early 1974, with operational testing being completed in November 1982. Full scale production began in April 1983, with the weapons initial US operating capability (IOC) being declared during US Fiscal Year (FY) 1983. The USN’s first operational rounds were deployed aboard the USS Kitty Hawk during January 1984. As might be expected, AGM-88 has gone through a number of iterations which Armada identifies as having been designated as the AGM-88A, -88B, -88C, -88E (the AARGM configuration which is dealt with separately) and -88F. In order, the 1983 vintage AGM-88A incorporated a fusable-link memory (necessitating the return of the missile’s guidance section to its manufacturer if its tactical software required change) and made use of Block I and II software, with the latter offering guidance and fuzing improvements. AGM-88B achieved its IOC during US FY 1986 and introduced an Erasable, Electronically Programmable, Read-Only Memory (EEPROM) that facilitated its embedded software being changed without having to disassemble it. Initially fitted with Block II software, a Block III update was introduced during 1989/1990. Follow-on Block IIIA software introduced a limited “geographic specificity” capability (that is, improved control over the missile’s geographic footprint), improved capabilities against emitter shutdown and use of ‘complex’ wave forms. The 1993 vintage AGM-88C introduced a new guidance section; improved receiver sensitivity; a larger memory; the WAU-27/B warhead; Blocks IV and V software updates and target-of-opportunity, pre-briefed, self-protection and range-known operating modes. Of these, range-known is only available to the EA-18G and those F-16s equipped with the AN/ASQ-213 emitter location system. Again, the 15.4ft (4.17m) long missile weighs 809lb (367kg) at launch and has a maximum range of better than 91km (56 miles). Last but not least, the USAF AGM-88F upgrade utilises Raytheon’s HARM Control Section Modification (HCSM) package that incorporates a GPS receiver, an improved inertial measurement unit, new circuit cards, a new power supply and a digital flight computer. Taking the family as a whole (and over time), HARM users include Australia (Boeing EA-18G), Germany (PANAVIA Tornado), Greece (F-16), Italy (Tornado), South Korea (General Dynamics F-16), Morocco (Boeing F-16), the RSAF (F-15), Spain (EF-18A), Turkey (F-16), the United Arab Emirates (F-16), the USAF (F-16), the US Marine Corps (F/A-18) and the USN (EA-18G and F/A-18).

AARGM on F_A-18
The AGM-88E AARGM missile utilises the same airframe envelope as earlier iterations of the AGM-88 HARM (USN)

To conclude (and as alluded to earlier), the US is on the cusp of introducing its fifth generation ARM in the form of the AARGM-ER variant of the AGM-88E AARGM missile. The USN describes baseline AARGM as being a medium-range, 15.4ft (4.17m) long, 795lb (361kg) iteration that utilises the legacy HARM’s rocket motor, warhead, wings and fins was a new guidance section (combining passive and active sensors) and a modified control section. As such, the configuration offers an expanded target set, a counter shut-down capability, improved emitter detection/location, geographic specificity and an impact assessment broadcast capability. At the time of writing, AARGM was being procured for the USN (EA-18G and F/A-18), Germany (Tornado), Italy  (Tornado) and Australia (EA-18G), with most rounds taking the form of existing inventory that has/is being upgraded. For its part, AARGM-ER development began during US FY 2016 and is aimed at creating a capability that has a longer range than baseline AARGM, increased survivability and improved effectiveness against future threats, with the whole making use of a new motor and a refined airframe shape. Within the USN, AARGM-ER is to be integrated with the service’s EA-18G and F/A-18E/F aircraft and, as noted earlier, the type is understood to be compatible with the F-35 family.

by Martin Streetly