The anti-radiation missile sector has seldom been so vibrant. New and upgraded weapons are entering the marketplace as a riposte to enhancements of ground-based air defences.
By Dr Thomas Whitington
The Spencer Davis Group and The Righteous Brothers were celebrating on 18 April 1966. Both bands had scored number one hits with their singles Somebody Help Me and (You’re My) Soul and Inspiration in the Britain and the United States.
Thousands of miles away in South-East Asia, the US was deeply embroiled in the Vietnam War. That day the USAF ushered in a new era in its history by employing the Texas Instruments AGM-45A Shrike Anti-Radiation Missile (ARM) for the first time.
The AGM-45 was used extensively during the Vietnam War by the USAF and US Navy. Eleven variants were produced, each of which used a different Radio Frequency (RF) seeker tuned to the waveband of the radar the missile was to attack. For example, the AGM-45A/B6 detected X-band (8.5GHz to 10.68GHz) radar emissions, principally those from the SNR-125 (NATO reporting name Low Blow) fire control radar forming part of the Almaz S-125 Neva/Pechora (SA-3 Goa) medium-range/medium-altitude surface-to-air missile ensemble.
Nor were the capabilities of the AGM-45 restricted to Soviet and Warsaw Pact radars. During the 1982 Falklands/Malvinas conflict, the RAF famously used AGM-45A missiles launched from Avro Vulcan-B2 strategic bombers against an Argentine Westinghouse AN/TPS-43F ground-based air surveillance radar and Oerlikon Contraves Skyguard fire control radars accompanying Oerlikon GDF anti-aircraft artillery systems. These radars were located on the island of East Falkland and were attacked on 31 May 1982 and again on 2 June 1982.
Aside from being the world’s first operational ARM, the AGM-45 had one of the longest careers of such a weapon, eventually leaving US service in 1992. It made way for the legendary Texas Instruments/Raytheon AGM-88 HARM (High-Speed Anti-Radiation Missile).
HARM IN ACTION
Just under one year after RAF use of the AGM-45, the US DoD approved the full rate production of the AGM-88. The missile subsequently made its combat debut during the Operation Eldorado Canyon airstrikes mounted by the USAF and US Navy on 15 April 1986 against targets in Libya in retaliation for the sponsorship of violent insurgent movements in the Middle East and beyond by the country’s then leader Colonel Muammar Gaddafi.
Some 34 years later, the AGM-88 shows no signs of heading for retirement. In fact, the weapon has evolved into two new variants – the Northrop Grumman AGM-88E Advanced Anti-Radiation Guided Missile (AARGM), and Raytheon’s AGM-88F HCSM (HARM Control System Modification), both of which augment the existing AGM-88B/C variants which entered service in 1987 and 1993 respectively.
The AGM-88E adds a global positioning system/inertial navigation system (GPS/INS) and a Millimetric Wave Radar (MMW) to the AGM-88B/C. The former helps a missile avoid the so-called ‘switch off’ tactic where radar operators deactivate their equipment to break the RF lock an ARM relies upon to guide towards its target. The GPS/INS allows the missile to be loaded with the precise coordinates of the radar so that, even if it is deactivated, the missile can use these coordinates to find its target.
Secondly, the GPS/INS can be programmed with a defined area beyond which the missile is not permitted to fly. It is noteworthy that during Operation Allied Force in 1999 – the NATO-led effort to end ethnic cleansing in the Balkans territory of Kosovo – an AGM-88B ended up hitting a street in a suburb of the Bulgarian capital Sofia after having lost its RF lock.
MMW radars, which transmit on frequencies of 30GHz and above, produce highly detailed imagery thanks to their very short wavelengths. This helps in the gathering of battle damage assessment as the MMW radar can transmit detailed imagery of the missile’s end game to verify the accuracy of the attack.
Customers for the AGM-88E include the German government procuring 91 examples for the Luftwaffe’s Panavia Tornado-ECR air defence suppression jets under a US$122m (A$192m) foreign military sale announced in 2019. These will replace the current AGM-88B/C missiles used on Tornado. AGM-88Es are also furnishing the Tornado-ECRs flown by Italy’s Aeronautica Militaire.
Closer to home, the RAAF is also acquiring the weapon, placing an initial order for 16 AGM-88Es in 2015 and an additional 10 in 2018, with plans afoot for a further 14.
On 8 March 2020 Northrop Grumman announced that it had secured a US$322.5m (A$508m) engineering and manufacturing development (EMD) contract for an extended range variant of the AARGM, called somewhat predictably the AGM-88G AARGM-ER. The contract covers the design, test, and integration of a new rocket motor for the baseline AGM-88E to enhance its range. Development of the AARGM-ER is being financed by the US Navy which could become a customer in the future.
The AGM-88F is also a reworking of the AGM-88B/C adding a GPS/INS to the baseline version of the missile. Customers for the AGM-88F include Bahrain, Qatar and Taiwan, with a US foreign military sale being concluded in May 2019 worth US$355m (A$560m). The contract also covers the upgrade of an unspecified number of USAF AGM-88C weapons to AGM-88F status. This work, and delivery of the AGM-88Fs to foreign customers, is expected to be completed by 2027.
These contracts build on the 650 AGM-88F missiles delivered to the USAF from a contract won by Raytheon in 2012. They are deployed on Lockheed Martin F-16CJ Viper Weasel air defence suppression aircraft.
Like the AGM-88E, the AGM-88F can be deployed both with and without the Raytheon AN/ASQ-213(V) HARM targeting system. This is used with dedicated air defence suppression aircraft to provide highly accurate emitter fire control information, uploaded into the missile before launch or during its flight via datalink.
USAF sources said the AN/ASQ-213(V) is used by aircraft such as the F-16CJ Viper Weasel to provide precise emitter location information during SEAD (suppression of enemy air defence) efforts. Use of the AGM-88 series without an ASQ-213(V) is more conducive to attacking hostile emitters in self-defence if an aircraft is illuminated.
Beyond the AGM-88, other countries are entering the ARM club. These include India where that country’s Defence Research and Development Organisation (DRDO) is realising the New-Generation Anti-Radiation Missile (NGARM).
Work started on this missile in 2012 and reports claim ranges of between 54nm (100km) to 65nm (120km), with the weapon expected to be deployed on Indian Air Force Sukhoi Su-30MKI and Hindustan Aeronautics Limited Tejas combat aircraft. Like the AGM-88E, it will include an MMW radar seeker, with the missile’s RF seeker expected to cover a waveband of 2GHz to 20GHz. Once development of the NGARM is complete, the missile may augment or replace the IAF’s Soviet-era Zvezda-Strela Kh-25MP (NATO reporting name AS-12 Kegler) ARMs.
While the IAF has been in the ARM club since the 1970s, the UK’s RAF bowed out in 2013 with the retirement of its British Aerospace/MBDA ALARM (Air-Launched Anti-Radiation Missile), a system which was last used in anger by the force during the 2011 NATO and US-led interventions in the Libyan civil war.
More recently, MBDA sources said the Royal Saudi Air Force (RSAF), which also acquired the ALARM for employment from its Tornado IDSs, may have used the weapon during its intervention in Yemen’s civil war, although against general land targets rather than radars.
The RAF is considering acquisition of MBDA’s SPEAR-EW (Select Precision Effects at Range-Electronic Warfare) variant of the SPEAR-3 air-to-ground missile. The SPEAR-EW design dispenses with the warhead and seeker of the SPEAR-3, replacing this with an electronic warfare payload. The EW payload comprises Electronic Support Measures (ESM) to detect, locate and identify hostile emitters, and an electronic attack system to blast these with jamming waveforms.
MBDA sources said that the SPEAR-EW could be used as a stand-in capability, jamming hostile radars while an aircraft such as the RAF’s Eurofighter Typhoon-F/GR4 combat aircraft are operating in contested airspace. The SPEAR-EW is able to loiter and perform electronic attack while the jet performs its mission, or can be used to identify and jam hostile emitters which could then be engaged by kinetic air-to-ground weapons such as the SPEAR-3.
Although not formally revealed, it is possible that the SPEAR-EW will jam emitters transmitting in wavebands of 8.5GHz to 40GHz, enabling it to jam X-band, Ku-band (13.4-14/15.7-17.7GHz), K-band (24.05GHz to 24.25GHz) and Ka-band (33.4GHz to 36GHz) ground-based and naval surveillance and fire control/ground controlled interception radars and missile radar seekers. The range of the SPEAR-EW is thought to be in excess of the 75nm (140km) of the SPEAR-3. MBDA sources have told the author that production and delivery of the SPEAR-EW could occur over the next five years should the RAF place a formal order.
Air-to-surface missiles have been the weapon of choice for attacking hostile radars, but Israel Aircraft Industries (IAI) has bucked this trend with the development of the Harpy anti-radar unmanned aerial vehicle (UAV) which is believed to have entered service with the Israeli Air Force around 1973.
Open sources state that the weapon has an endurance of about six hours and carries a blast fragmentation warhead. After launch, it will loiter at an altitude of 6,500 feet and use an ESM to detect emissions from hostile radars. Once an emitter is detected, the Harpy will dive towards the radar and detonate.
Taiwan has taken a similar approach with the realisation of its Anti-Radiation UAV (ARUAV). Few design details have been released, although in 2017 it was reported that the weapon can loiter for 100 hours. Although not publicly revealed, sources claim the ESM equipping the ARUAV covers a waveband of at least 2GHz to 18GHz.
This may have been extended further downwards to frequencies of 500MHz allowing the ARUAV to detect emissions from ultra-high frequency (UHF) radars transmitting on L-band wavelengths of 1.215GHz to 1.4GHz. These frequencies are used by the People’s Republic of China’s (PRC) East China Research Institute of Electronic Engineering’s JY-14 ground-based air surveillance radar, alleged in some reports to be capable of detecting and tracking combat aircraft with low radar cross-sections. The JY-14 is reportedly the most numerous such radar in service in the PRC.
CHINA and RUSSIA
Like its rival across the Taiwan Strait, the PRC is pouring investment into ARM technology. Details are sparse regarding the performance of the Hongdu Aviation Industry Corporation YJ-91 ARM, but it is thought to have been developed from Russia’s Tactical Missiles Corporation’s Kh-31 (NATO reporting name AS-17 Krypton) air-to-surface weapon.
The Kh-31P ARM variant can be outfitted with a number of distinct RF seekers depending on the radar the missile is to attack. The PRC has developed an indigenous variant of the weapon – known as the KR-1 and thought to have been equipped with a single RF seeker optimised for detecting and homing in on S-band (2.3GHz to 2.5GHz/2.7GHz to 3.7GHz) ground-based air surveillance radars.
One of the principle differences between the baseline KR-1 received by the PRC in 1997 and the YJ-91 is the latter’s single RF seeker covering a wide waveband of emitters, in contrast to the KR-1’s restriction to S-band. This will allow the missile to cover, roughly, the 2GHz to 18GHz waveband used by most ground-based air surveillance, naval surveillance, and fire control/ground-controlled interception radars – the priority targets during SEAD missions. Alongside the expanded frequency range of the YJ-91, the missile may have a slightly extended range of 65nm (120km) versus the 59nm (110km) of the Kh-31P.
Since its service entry in 1991, the Kh-31P has been developed into several subvariants. Three distinct models have been identified, the Kh-31P, Kh-61PK and Kh-31PD. The Kh-31PK offers improved lethality over the Kh-31P with a proximity-fused warhead. Meanwhile, the Kh-31PD extends the missile’s range to 135nm (250km). Each of these missiles is still thought to use multiple RF seekers – reportedly designated L-111, L-112 and L113 collectively – covering a 1GHz to 11GHz waveband. All Kh-31P variants are used with the L-080/L-081 Phantasmagoria-A/B emitter locator system which works in a similar fashion to the HARM’s AN/ASQ-213(V)
In Russian service the Kh-31P series has been augmented by the Kh-58E/UShKE (NATO reporting name AS-11 Kilter) missile which has a reported range of up to 132nm (245km) and is capable of targeting radars emitting on frequencies of 1GHz to 12.5GHz. Alongside the Kh-58E/UShKE, the International Institute of Strategic Studies’ 2020 Military Balance noted that the Zvezda-Strela Kh-25M/MP (NATO reporting name AS-10 Karen) continues in service with the Russian Air Force, having been introduced in 1975. No details appear to have been released regarding the wavebands covered by the missile although, like the Kh-31P, it is thought to use an array of RF seekers which must be fitted to the missile prior to a sortie according to the radar being targeted.
The prevailing paradigm of near-peer rivalry is spurring investment into ARM technology. The US and its allies, and the PRC and Russia, all field sophisticated ground-based air defences, particularly radar. As a result, defeating such threats becomes an imperative for success in the wider offensive counter air (OCA) battle.
Success will belong to those who can outclass the technological sophistication of an adversary’s radar, particularly in terms of the electronic counter-countermeasure (ECCM) techniques these can bring to bear through the technological sophistication of their ARMs. Similarly, countries such as India and Taiwan are more than aware of the importance of these weapons and are making investments accordingly. Not only will this help them develop capabilities independent of their traditional suppliers, but also help them to emerge as exporters of such materiel in their own right.