Europe has embarked on an ambitious airborne electronic attack programme; a timely capability to counter a growing threat.
Standby for acronyms: The European Defence Agency’s (EDA) Airborne Electronic Attack (AEA) initiative is one of the agency’s Permanent Structured Cooperation (PESCO) programmes. The EDA is a European Union (EU) body tasked with facilitating and promoting EU member state integration. The agency works to develop pan-EU defence capabilities and military cooperation. It is also tasked with strengthening Europe’s defence industry, and defence research and technology base. Key to this are the EU’s PESCO projects. Launched in 2017, permanent structured cooperation emanates from the 2012 Lisbon Treaty of European Union. Article-42 sets out the EU’s Common Security and Defence Policy (CSDP). CSDP “shall be an integral part of the (EU’s) common foreign and security policy.” Clause 3 of the treaty states that “(m) ember States shall undertake progressively to improve their military capabilities.” This includes strengthening the union’s defence sector technological and industrial base.
PESCO
On 11 December 2017 the EU Council took the decision to establish the PESCO arrangement. The European Council comprises the EU’s heads of state or government. It sets the EU’s overall priorities and political direction. In the EDA’s words Permanent Structured Cooperation “offers a legal framework to jointly plan, develop and invest in shared capability projects, and enhance the operational readiness and contribution of (the EU’s) armed forces.” This makes sense. According to the EDA, the combined defence budgets of the EU’s membership in 2021 was over $253 billion in 2023 values. This is still a fraction of the 2023 US Defence Authorisation Act which hands the US Department of Defence (DoD) almost $817 billion. The budget levels of European powers will simply not allow unilateral development and acquisitions of complex defence systems. Collaboration is the way forward and this is reflected in the PESCO philosophy.
The EDA has 60 ongoing PESCO projects. These cover an array of capabilities from provision of medical care and the construction of new corvettes, to rotorcraft docking stations for Uninhabited Aerial Vehicles (UAVs). The AEA PESCO is being led by Spain which is also a project member alongside France, Italy, Germany and Sweden. “The project covers the design, development and testing of a (stand-off and stand-in) multi-jamming capability,” according to AEA project literature. Other stipulations state the jamming architecture realised via the project will be installed internally onboard a combat aircraft and/or carried in a podded configuration. The latter configuration will let the architecture be easily swapped between inhabited aircraft and UAVs. Open software standards are also required to allow the architecture to easily accept improvements.
Gravestones and Cheese Boards
To understand how the jamming system might work in practice consider the Russian armed forces’ S-400 (NATO reporting name SA-21 Growler) high-altitude, long-range Surface-to-Air Missile (SAM) system. This is arguably the most dangerous ground-based air defence threat in Europe today. North Atlantic Treaty Organisation (NATO) and EU members would face it in any future showdown with Russia. S-400 batteries are equipped with the 92N2E/6E (NATO reporting name Gravestone) X-band (8.5 gigahertz/GHz to 10.68GHz) ground-based air surveillance radar. Open sources say this radar has an instrumented range of 216 nautical miles/nm (400 kilometres/km). It would comb the skies for incoming air threats.
While the Gravestone is primarily tasked with detecting and tracking low altitude targets, the S-400’s accompanying 96L6 (Cheese Board) C-band (5.25GHz to 5.925GHz) radar is intended for high altitude targets. It has a reported instrumented range of 162nm (300km). Any target unlucky enough to be detected could find itself on the receiving end of the S-400’s missiles. These have a similarly long reach. The 40N6E SAM has a 216nm range. It can reach 98,000 feet/ft (30km) altitude and speeds of 2,334 knots (4,322 kilometres-per-hour).
It is imperative that any combat aircraft prevents the S-400 detecting and tracking it in the first place. Without radar data on the target’s speed, altitude, bearing and location, the S-400’s lethality is seriously degraded. Combat aircraft carry jammers transmitting powerful interference. Like static on an old television set, this sends a jamming signal into a radar so powerful that the real radar echo of the aircraft is subsumed beneath this noise.
While noise jamming is still used regularly to outfox radars, more sophisticated techniques are in routine use. The advent of the microchip in the 1960s, and subsequent advances in computing, precipitated the Digital Radio Frequency Memory (DRFM). DRFMs listen for an incoming hostile radar signal, alter that signal in a particular way and transmit it back to the radar.
All radars transmit a radio signal on a particular frequency which travels at the speed of light, 161,595 knots-per-second (299,274 kilometres-per-second). It hits an object like an aircraft and is reflected to the radar. The radar takes the time for the signal’s round trip from the radar antenna to the target and back again. This is divided by two to ascertain the target’s range. If the round trip takes 0.5 milliseconds, the entire distance will have been 42.7nm (79.1km) nautical mile. Divided by two, this gives a range of 21.4nm (39.6km).
The radar will also ascertain a target’s speed and bearing using the Doppler Effect. This can be observed when the pitch of a police car’s siren seems to rise as it approaches and lowers as it passes by. All radio signals follow a wave pattern with peaks and troughs. Frequency is a measurement of how many of these peaks and troughs occur per second. The peaks and troughs of the radar’s echo from a target take progressively less time to reach a radar’s antenna as the target approaches and vice versa. Radar software measures this Doppler Shift, as it is known, giving details of the target’s bearing and speed.
A DRFM samples the incoming radar signal. It then composes a fake radar echo which is transmitted back to the radar. For all intents and purposes, to the radar this will seem like the kind of echo it would expect to receive from the target it has detected. However, it will contain false information. Perhaps the DRFM has modified the Doppler Shift, giving the target a faster or slower speed than in reality. Perhaps the bearing has been altered? The radar is still receiving the true echoes from the target, but also false echoes from the DRFM. Will the radar operator know which one is real? The DRFM may even replicate a myriad of false echoes. Now the operator has scores of airborne targets to deal with, once again not knowing which ones are real. These are just a small selection of the headaches a DRFM can cause a radar operator.
Combat aircraft employ two approaches when it comes to using Electronic Countermeasures (ECMs) to jam a hostile radar. An aircraft is likely to carry its own jammer providing a ‘bubble’ of jamming around the aircraft, using both conventional and DRFM jamming techniques for protection. Packages of aircraft may benefit from escort jammers. These are usually pod-mounted systems providing similar levels of protection, but across a larger area which covers the volume of sky occupied by the whole package. Examples of escort jammers in service, or entering service, with NATO and allied air forces include Israel Aerospace Industries’ EL/L-8222SB Scorpius, EDO Corporation/L3 Harris AN/ALQ-99, Elettronica’s EDGE pod, Hensoldt’s Kalætron, Indra’s ALQ-500P, Leonardo’s Common Jamming Pod, Northrop Grumman’s AN/ALQ-131, Rafael Advanced Defence Systems’ SkyShield, Raytheon’s AN/ALQ-249 Next Generation Jammer-Mid Band and Saab’s Arexis.
Deception jamming a DRFM can perform is often used to protect individual aircraft with noise jamming used when escorting packages of aircraft. Generally speaking, more jamming power is needed for stand-off jamming than stand-in jamming. This is because with the latter signal needs more power for two reasons: Firstly, the jamming signal needs the range to reach the targeted radar. Secondly, once at the radar the signal needs to sufficient power to drown out the echoes from potential targets.
AEA
Official literature covering the AEA initiative says that as well as providing conventional jamming, the capability will support Cyber and Electromagnetic Activities. Better known as CEMA this philosophy is converging some elements of cyber and electronic warfare. This makes sense. Few radars or communications systems are analogue these days. Instead, they depend on digital technology and IP (Internet Protocol) data. Inject a cyberattack into either of these systems and you can do some serious damage. Usefully, radios and radars have antennas through which the malicious code can be delivered. Instead of performing conventional jamming the signal transmitted by the jammer becomes the delivery system for the nefarious code. The code is injected into the radar via its antenna. Once there, it can alter the radars’ operations. This may cause an immediate and obvious degradation to the radar’s performance. It could force it to cease operating altogether.
Alternatively, the code may mess around with the radar’s signal processing. This could present false or misleading targets to the radar operator. It may alter height, range or bearing information for the real targets on the operator’s screen. As with the DRFM tactic, this could be so subtle that it might not be immediately obvious. Injecting a cyber attack via a radar or radio has another potential benefit. Ground-based air surveillance radars and the radio communications air defenders depend on are often networked. The cyber attack could be injected via the radar or radio antenna but then move through the network. In doing so it could infect battle management systems used for air defence command and control. This could have predictably disastrous consequences.
Many specificities regarding the AEA design remain unknown. Repeated requests for more information from the EDA and from the PESCO’s industrial partners went unanswered. Open sources say that the pod will use Active Electronically Scanned Array (AESA) technology. This avoids having to physically move the jammer’s antenna to point it towards the threat. Electronic warfare moves at the speed of light and it is helpful if high-powered jamming beams can be pointed towards the threat at similar velocities. The pod will provide 360 degrees’ coverage. As the signals are electrically steered, a single pod can generate several jamming beams in several directions jamming several threats. The programme is being led by Indra. Elettronica is also involved alongside Hensoldt, Saab and Thales.
REACT
Open sources continue that the capability will cover frequencies of at least two gigahertz/GHz to 40GHz. This encompasses frequencies routinely used by ground-based air surveillance and fire control/ground-controlled interception radars used for ground-based air defence. European Commission documents refer to an AEA work strand called REACT (Responsive Electronic Attack for Cooperative Tasks). REACT is intended to attack low frequency radars but few additional details are provided. It makes sense to have a jamming capability against such radars. The Russian Air and Space Force (RSAF) is an enthusiastic user of low frequency radars. Its Voronezh ground-based air surveillance radars transmit on Very High Frequencies of 150MHz to 200MHz. Such frequencies would fall out of the two gigahertz to 40GHz waveband.
Publicly available figures for the Voronezh radars give them a range of circa 3,240nm (6,000km). What makes them particularly dangerous is their frequencies let them detect aircraft with low Radar Cross Sections (RCS). Contemporary European combat aircraft like the Eurofighter Typhoon or Dassault Rafale family have RCSs of between 0.1 and 0.5 square metres. For sixth-generation combat aircraft like the FCAS and BAE Systems’ Tempest they will be even lower. Voronezh radars would be unable to provide detailed enough target information to guide SAMs to such targets. However, they could provide a reliable indication where such aircraft are at some considerable range. RSAF fighters could then be scrambled and vectored towards these areas in anticipation.
Almost no details exist in the public domain regarding when the AEA architecture may enter service and its current level of development. As platforms like the FCAS will enter service early next decade according to reports, the pod will need to be ready for service by then. Given the resurgence of the Russian air defence threat in Europe it might be wise to have this defending European airpower much earlier.
by Dr. Thomas Withington
