Electronic Intelligence (ELINT)

Electronic intelligence, briefly known as ELINT (Electronic Intelligence), is the acquisition of intelligence from electromagnetic signals that do not contain speech or text. It typically encompasses signals emitted by electronic sources such as radar, radio, navigation systems, and weapons systems. In ELINT operations, passive electronic signals are detected, recorded, and analyzed using specialized receiver sensors. This method provides information about enemy capabilities—for example, the location and characteristics of radars—and enables threat assessments. The collected data helps understand the enemy’s intentions and capacities, thereby facilitating the development of countermeasures. ELINT is one of the subdisciplines of the broader intelligence field known as signals intelligence (SIGINT). Another major subdiscipline is communications intelligence (COMINT), which targets communication content such as human speech or written messages. In contrast, ELINT focuses primarily on electronic system signals such as radar, seeking to decipher the enemy’s electronic warfare architecture.

History

Development of ELINT in Türkiye

The development of electronic intelligence in Türkiye has largely been shaped by cooperation with allies during the Cold War years and subsequent advances in the domestic defense industry. Following the 1974 Cyprus Operation, ASELSAN (established in 1975) laid the foundation for Türkiye’s efforts to develop indigenous technologies in electronic warfare and intelligence.

For many years, a unit operating under the name General Staff Electronic Systems (GES) Command within the Turkish Armed Forces was responsible for collecting and evaluating signals intelligence. In 2012, the GES Command was transferred to the National Intelligence Organization (MİT), initiating centralized coordination of ELINT and broader SIGINT activities under a single civilian intelligence agency. This transition aimed to improve the effective management of domestic and foreign electronic intelligence operations. Since the 1990s, MİT and the Turkish Armed Forces have developed capabilities such as satellite communications monitoring and cross-border electronic surveillance. Türkiye’s defense industry has also evolved to produce various ELINT systems. In particular, ASELSAN has developed Electronic Support (ES) systems for multiple platforms.

For example, under the MİLGEM project, ASELSAN’s ARES-2N electronic support/ELINT systems have been integrated into national warships. These systems enable ships to passively detect and identify enemy radar and electronic transmissions. Türkiye has also enhanced its signals intelligence capabilities through unmanned aerial vehicles (UAVs) and other aerial platforms during the 2000s and 2010s. The recently developed HAVA SOJ project (Stand-Off Jammer from Air) aims to integrate electronic warfare and intelligence systems onto specialized jet platforms to remotely disrupt and monitor enemy communications and radar. In this context, ASELSAN has developed a system on Bombardier Global 6000-type jets equipped with powerful radar jammers and receivers. Türkiye has also achieved real-time signal collection capabilities in the field through UAV-based ELINT platforms such as ANKA-İ. For instance, a specially configured Anka-S UAV has been used as an airborne electronic signal collection platform over areas such as Syria and Libya, transmitting detected target data to other UAVs. Thus, ELINT in Türkiye has evolved from a limited capability reliant on allied support into a comprehensive capability deployed across land, air, sea, and space platforms through indigenous means.

Historical Development of ELINT Worldwide

The foundations of electronic intelligence extend back to World War II. The invention and widespread military use of radar created an urgent need to detect and analyze these radar signals. The beginning of modern ELINT can be traced to Allied efforts during World War II to detect and analyze German radar systems. In the early years of the war, British intelligence officers conducted covert listening operations to identify German “Freya” and “Würzburg” radars and develop countermeasures. During this period, Bletchley Park in the United Kingdom not only broke communication codes but also led in the tracking of electronic signals. In the postwar era, electronic intelligence became a critical element of Cold War competition. In 1946, the UKUSA Agreement signed between the United States and the United Kingdom initiated an official alliance for electronic intelligence sharing. This agreement was expanded in 1956 with the inclusion of Canada, Australia, and New Zealand, forming the multinational signals intelligence network known as the Five Eyes. The Five Eyes alliance ensured that member countries shared global electronic surveillance data under a mutual non-surveillance agreement. The backbone of this alliance consists of institutions such as the U.S. National Security Agency (NSA) and the United Kingdom’s Government Communications Headquarters (GCHQ).

The United States took a major step toward consolidating signals intelligence under a single authority with the establishment of the NSA in 1952. While the integration of ELINT into the NSA was debated during its formation, initially ELINT activities in the U.S. continued to be conducted separately within different branches of the military. By the mid-1950s, presidential-level reports recommended bringing ELINT under the NSA umbrella, leading to strengthened coordination of ELINT within the U.S. defense establishment. Throughout the Cold War, the United States allocated substantial resources to monitor Soviet electronic warfare systems. For instance, the GRAB and POPPY satellite programs, initiated in the early 1960s, successfully captured Soviet air defense radar signals from space. These were among the first examples of satellites being used for ELINT purposes and provided critical data for understanding Soviet radar capabilities. Meanwhile, the Soviet Union also established similar electronic intelligence networks. The Soviet military intelligence agency GRU and the intelligence service KGB tracked Western military communications and radar emissions through numerous listening stations across the Eastern Bloc and globally. The Soviets closely monitored American military and diplomatic communications using listening stations established on allied territories such as Cuba. Additionally, in the 1960s, the Soviet Union took a step into space-based electronic intelligence by launching its own ELINT satellites, such as the Tselina series.

In the bipolar environment of the Cold War, traditional espionage and human intelligence were led by services such as the U.S. CIA and the British MI6, while electronic intelligence was primarily conducted by technical agencies such as the NSA and GCHQ. However, strategic-level ELINT intelligence was utilized by the CIA and MI6 for operational planning. Many critical events in the second half of the 20th century underscored the importance of ELINT. For example, in 1960, the Soviet Union shot down an American U-2 spy plane flying over its territory, largely by detecting it with radar systems. This incident triggered the development of more advanced radar warning receivers and countermeasure systems.. During the Vietnam War, after U.S. forces encountered Soviet-made SA-2 surface-to-air missiles, they developed receiver systems (RWR) and electronic jamming equipment to detect and warn against enemy radars, thereby reducing losses.

By the 1990s, electronic intelligence sharing had become more institutionalized in the Western world. In addition to the Five Eyes countries, several NATO allies partially joined this network. This cooperation, known as SIGINT Seniors Europe (SSEUR) and informally expanded as the “Fourteen Eyes,” integrated countries such as France, Germany, Spain, Italy, the Netherlands, Belgium, Denmark, Sweden, and Norway into the U.S.-U.K.-centered electronic intelligence sharing framework. Thus, collective ELINT activities continued even after the Cold War against shared threats such as Russia and China. For example, when the global surveillance program known as ECHELON became public in the early 21st century, it revealed the extensive infrastructure built by the Five Eyes alliance to intercept satellite communications and radar signals. Edward Snowden’s disclosures in 2013 further demonstrated the extent to which electronic surveillance had expanded in the digital age.

Today, countries such as the United States, the United Kingdom, Russia, China, Israel, and Germany all possess advanced ELINT capabilities. Israel’s renowned Unit 8200 has been among the world’s most effective units in electronic intelligence and cryptography since the 1950s. China has rapidly expanded its space and cyber electronic intelligence capacity through structures such as the Strategic Support Force, established in 2015. In Russia, the FSB—the successor to the KGB—and the separate military intelligence agency GRU use advanced satellites, listening ships, and large ground-based receiver stations to monitor modern communication and radar systems. This historical trajectory demonstrates that ELINT has become an indispensable element in the international security balance.

Core Concepts and Components

ELINT and Other Intelligence Types: Electronic intelligence (ELINT) is broadly categorized under signals intelligence (SIGINT). SIGINT is a broad field aimed at acquiring intelligence from all electromagnetic signals emitted by an adversary. It is divided into two main branches: ELINT and communications intelligence (COMINT). COMINT focuses on intercepting and decrypting adversary communications such as telephone, radio, and satellite transmissions (speech, text, data transfers), while ELINT targets electronic signals outside of communication. For example, waves emitted by an air defense radar fall under ELINT, whereas conversations among the radar’s operators fall under COMINT. This distinction is crucial because the technical methods and areas of expertise differ. ELINT requires extensive knowledge of electronic engineering and radar theory, while COMINT demands proficiency in language, cryptography, and communication protocols. Nevertheless, both branches often operate together to form the complete SIGINT framework and complement each other.

Technical Methods: The foundation of ELINT operations lies in passive listening techniques. Passive listening relies solely on receivers to capture signals emitted by a target electronic system without transmitting any signal itself. This allows the electromagnetic emissions to be detected without the target being aware of being monitored. ELINT sensors are receivers capable of scanning across very wide frequency bands. For instance, a warship’s electronic support system continuously scans surrounding radar signals and records those exceeding a certain threshold. Technical procedures such as frequency analysis, amplitude analysis, pulse (pulse train) analysis, and modulation detection are then performed on the collected signals. These analyses help determine which device the signal likely originates from. For example, the interval between pulses and their frequency can reveal whether the signal comes from an air search radar or a missile guidance radar. Direction finding (DF) methods are also a critical component of ELINT. Receiver antennas capable of determining the direction from which a signal arrives (such as goniometric antenna arrays) can pinpoint the source’s location by triangulating the same signal received from multiple positions. This enables the mapping of enemy radar or transmitter locations, providing target data for countermeasures such as electronic warfare or missile strikes. ELINT can sometimes support active methods; for example, signal parameters gathered during the “electronic support” phase feed into the subsequent “electronic attack” (jamming/deception) phase. However, active electronic warfare (such as radar jamming) is not itself considered ELINT; rather, ELINT constitutes the preceding detection and support phase. Therefore, ELINT is often referred to as “Electronic Support (ES)” or “Electronic Support Measures (ESM)” and is distinct from jamming (ECM) and electronic attack.

ELINT specialists compare collected signals against a library of known signal patterns. These records serve as the “signal fingerprints” of previously identified radars and other systems. If a match is found, the signal type is immediately identified; if no match is found, it likely indicates a new threat, and the signal parameters are examined in detail by technical intelligence units. These activities, known as technical ELINT (TechELINT), analyze the structure of the signal to develop appropriate countermeasures—for example, optimal satellite orbits, suitable radar warning receivers for aircraft, or counter-guidance methods for missiles. Another dimension of ELINT is operational ELINT (OpELINT), which reveals where and when an adversary’s electronic systems are active, their routine patrol patterns, and their on/off schedules. This information contributes to the creation of an Electronic Order of Battle (EOB), which provides commanders with a picture of how enemy sensors are deployed.

Platforms and System Examples: Electronic intelligence can be conducted through various platforms:

• Ground Stations: Strategic ELINT is typically conducted via fixed listening facilities. Ground stations equipped with large antenna arrays can monitor overseas broadcasts or satellite transmissions. For example, during the Cold War, the United States and its allies operated listening posts in various countries, including Türkiye, to track Soviet radar and communication signals. Sites such as the RAF Menwith Hill station in the United Kingdom or U.S. facilities in Alaska serve as ELINT centers capable of monitoring vast areas. Signals are collected at these facilities using highly sensitive receivers and parabolic antennas and then transmitted to central analysis units.

• Satellite Systems: Space-based ELINT is an indispensable tool for major powers due to its ability to cover vast geographic areas. Since the 1960s, U.S. ELINT satellites such as the GRAB and Canyon series mapped the Soviet air defense radar network from orbit. Similarly, the Soviet Union developed its own “Tselina” satellites to monitor the radar and radio emissions of U.S. Navy ships in the Pacific. Modern satellites, thanks to digital receivers and large memory capacities, can simultaneously scan and store numerous different frequencies. Raw data collected by satellites is downlinked to ground stations, filtered, and distributed to relevant units.

• Aerial Platforms: Aircraft, UAVs, and balloons are frequently used for ELINT. Aircraft, particularly due to their high altitude and long range, can detect electronic emissions while flying near or within international airspace over enemy territory. Specialized aircraft designed for this purpose are typically large-bodied with extended endurance. The U.S. RC-135 Rivet Joint aircraft are a classic example. Equipped with extensive sensor systems and a large mission crew (over 30 personnel including electronic warfare officers, linguists, and intelligence analysts), Rivet Joint aircraft can detect, identify, and geolocate radar, missile, and communication signals in real time within their operational area. Similarly, Russia’s Il-20M and newer Tu-214R electronic intelligence aircraft are equipped to monitor enemy electronic activities in operational zones. Israel has also converted Gulfstream G550 business jets into ELINT platforms (e.g., Nachshon-Shavit aircraft), gaining extensive electronic surveillance coverage across the Middle East. Unmanned aerial vehicles are increasingly gaining importance; strategic UAVs can remain airborne for long durations to monitor overseas electronic emissions. For example, the U.S. has equipped certain variants of the RQ-4 Global Hawk UAV with advanced signals intelligence sensors. Türkiye’s ANKA-İ platform has similarly performed continuous surveillance and signal collection missions over overseas operational areas.

• Maritime Platforms: ELINT also plays a significant role in navies. Warships, particularly destroyers and frigates, can detect radar signals from hundreds of kilometers away while underway, thanks to onboard Electronic Support Systems. This allows a ship task group to identify the location of offshore air defense radars in advance and detect threats at long range. Additionally, some countries operate specialized intelligence vessels. For example, Russia’s Balzam-class intelligence ships or the U.S. USS Pueblo (seized by North Korea in 1968) collected coastal nations’ transmissions while patrolling open seas. Submarines can also listen to enemy radars by raising antennas to periscope depth.

In summary, ELINT systems can be deployed across a wide spectrum, from fixed ground installations to satellites in space. The common objective is to trace the electromagnetic signatures left by adversaries to discover the “eyes” and “ears” of their radars, missiles, and communication networks.

Modern Systems and Applications

ELINT Systems and Projects in Türkiye

In recent years, Türkiye has made significant progress in developing and integrating its own ELINT systems alongside advances in its defense industry. ASELSAN is one of the leading companies in this field, producing various electronic support systems usable on land, sea, and air platforms.

A prominent land-based system is the KORAL Mobile Electronic Warfare System developed by ASELSAN. Although KORAL is primarily known as an electronic attack (jamming) system, it incorporates powerful electronic support (ES) capabilities. The KORAL system can detect and identify radars several hundred kilometers away and then jam them. In 2020, during conflicts in Syria’s Idlib region and in Libya during the defense of Tripoli, the KORAL system was actively deployed. In these operations, KORAL was used to blind enemy air defense radars while simultaneously recording their emitted signals, providing Turkish forces with a real-time threat picture. For instance, it was reported that in Idlib, KORAL neutralized and located Russian-made Pantsir and Kub/Kvadrat missile systems’ radars.

On maritime platforms, modern ED/ELINT systems are installed on Reis and Barbaros-class frigates and MİLGEM corvettes. ASELSAN’s nationally developed ARES-2N electronic support system serves as the primary ELINT sensor on MİLGEM vessels. This system scans 360 degrees around the ship, identifies detected signals by comparing them against a library, and classifies threats. Thanks to the ARES-2N system, Turkish warships can detect potential threats such as air search radars or guidance radars at long distances, enabling early engagement chains.

On aerial platforms, Türkiye is investing in aircraft capable of conducting stand-off electronic intelligence from long distances. Under the HAVA SOJ program, high-power receivers and jammers integrated onto specialized business jet platforms (Bombardier Global series) are set to enter the inventory of the Turkish Air Force. HAVA SOJ aircraft will be able to detect enemy emissions from hundreds of kilometers away while flying beyond the border or within friendly airspace and, if necessary, jam them. These aircraft use jointly developed mission systems by ASELSAN and TUSAŞ, positioning Türkiye among the few nations capable of conducting airborne ELINT and electronic warfare. The first HAVA SOJ aircraft are expected to enter service around 2024–2025. HAVA SOJ will serve as a force multiplier, particularly in the early detection and neutralization of strategic air defense systems such as the S-400 and Patriot.

In the field of unmanned aerial vehicles, Türkiye has gained new flexibility by integrating ELINT capabilities into UAVs. A concrete example is the ANKA-İ (Intelligence variant), developed by Turkish Aerospace Industries (TUSAŞ). The Anka-İ can detect and record enemy radar and communication signals along its flight path using onboard electronic intelligence pods. According to media reports, Anka-İ has been successfully deployed in Syria and Iraq operational areas; collected signals have been transmitted in real time to command centers and stored for later analysis. It is also reported that certain configurations of Baykar’s Bayraktar TB2 UAVs possess signals intelligence capabilities. For instance, TB2s equipped with electronic support pods can detect ground radars or enemy communication devices on the battlefield. Indeed, during the 2020 Nagorno-Karabakh War, Turkish-provided UAVs served not only as strike assets but also as central elements of the reconnaissance-intelligence architecture. In these conflicts, Turkish UAVs helped determine the positions of Armenian defense lines, disabled their radars (in conjunction with KORAL), and transmitted real-time intelligence to fire support units, thereby shaping the battlefield.

Leading ELINT Systems Worldwide

At the global level, advanced aerial platforms lead modern ELINT systems. The RC-135V/W Rivet Joint is the U.S. Air Force’s primary strategic ELINT aircraft. Continuously modernized since the 1960s, these aircraft have formed the backbone of signals intelligence in nearly every conflict from the Vietnam War to operations in Iraq and Syria. Equipped with wide-band receivers and advanced electronic processors, Rivet Joint aircraft can capture and analyze all radar, missile, and communication signals in their operational area in real time. They instantly share collected data with tactical units and command centers, ensuring shared operational awareness. The United States also conducts tactical-level ELINT using platforms such as the converted maritime patrol aircraft EP-3 Aries and smaller-scale RC-12 Guardrail aircraft.

On the Russian side, Soviet-era Il-20M “Coot” electronic intelligence aircraft served for many years but are now gradually being replaced by the newer Tu-214R jets. The Tu-214R features modern sensors and digital receivers capable of collecting ground and airborne target emissions with high precision. Russia also conducts tactical-level ELINT using UAVs such as the Orlan-10 and strategic-level ELINT via the Liana satellite system.

Israel, despite its small size, possesses one of the world’s most advanced ELINT capabilities. The Israeli Air Force’s Nachshon-Shavit and next-generation Oron aircraft are advanced platforms that integrate electronic intelligence with imagery intelligence. These systems, operated by Unit 8200, can track in real time the electronic signatures of potential threats in the Middle East, such as missile launchers and air defense systems. Israeli defense company IAI Elta also offers ELINT/COMINT products on the global market through its ELI-SIGINT series systems (e.g., ELI-3302 or integrated solutions named Orion). As a result, some allied nations equip their business jets or UAVs with Israeli-made sensors.

Meanwhile, the People’s Liberation Army has recently enhanced its ELINT capabilities across multiple platforms. The Y-9JB (GX-8) electronic intelligence aircraft collects electronic emissions from foreign navies and neighboring countries while patrolling China’s coastal waters and the South China Sea. China is also active in space-based surveillance, equipping some of its “Yaogan” reconnaissance satellites with electronic sensors. These satellites aim to observe the radar and communication networks of the United States and its allies in the Indo-Pacific region.

Among NATO allies, the United Kingdom has integrated the RC-135W Airseeker (the British version of the Rivet Joint) into its inventory, establishing an integrated strategic ELINT structure with the United States. Germany previously operated ELINT platforms converted from Breguet Atlantic and Transall C-160 aircraft and now plans to shift toward unmanned systems (the EuroHawk project was one such initiative, though it was canceled). France conducted long-term electronic intelligence collection over Africa and the Middle East using DC-8 Sarigue and later Transall Gabriel aircraft and is now transitioning to jet-based ELINT aircraft under the new Archange program.

Today, leading ELINT systems are not only large platforms but also distributed sensor networks. For example, within the U.S. integrated air defense network, F-35 fighter jets function as mini-ELINT nodes using their advanced sensors to instantly share detected radar signals via Link-16. Similarly, modern submarines have become capable of detecting surface ships using radar by integrating electronic support systems into their periscopes. These examples demonstrate that ELINT has now permeated platforms at every scale.

Strategic Importance and Future Outlook

ELINT is one of the invisible yet indispensable elements of modern military operations. At the strategic level, a nation’s ELINT capability enables it to learn in advance the “electronic behavior” of potential adversaries and prepare accordingly. Its role in military operations is critical: target detection and identification cannot be conceived without ELINT. For example, in an air operation, if the locations and frequencies of enemy air defense radars are determined in advance through ELINT, they can either be avoided or destroyed in the first wave. Indeed, during the 1991 Gulf War, the United States largely identified Iraq’s radar network before the war began and suppressed these radars through “Wild Weasel” missions to establish air superiority. Early warning is another vital contribution of ELINT: friendly forces can instantly learn when an enemy radar activates or a missile guidance radar turns on and take countermeasures. ELINT data also plays a major role in ballistic missile defense; telemetry signals or rocket motor tracking indicators emitted during missile launches can be intercepted to provide early warnings (this area is sometimes referred to as FISINT – Foreign Instrumentation Signals Intelligence, particularly for missile test telemetry).

Hybrid Warfare and Cyber-ELINT Integration: Modern conflicts are increasingly taking on a hybrid character, with conventional military elements merging with cyberattacks and information operations. In this new environment, a convergence is emerging between ELINT and cyber intelligence. States can monitor an adversary’s electronic emissions not only to gather military intelligence but also to obtain clues about critical infrastructure. For example, unusual activity in a country’s air defense radars could signal that it is under cyberattack. Conversely, a compromised enemy communication network, when combined with ELINT data, can produce a more comprehensive electronic warfare picture. Cyber-ELINT integration is becoming especially important in the era of 5G and the Internet of Things. In a world where billions of devices communicate wirelessly, intelligence can be gathered not only from traditional military radars but also from civilian networks. This situation is expanding the concept of ELINT toward a paradigm of “ubiquitous electronic surveillance.”

Artificial Intelligence-Based ELINT: As the electronic warfare domain becomes increasingly complex, the volume of collected signal data can exceed the real-time analytical capacity of human analysts. Therefore, artificial intelligence and machine learning techniques are being integrated into ELINT analysis. AI-based ELINT systems can rapidly scan massive volumes of raw signal data and detect previously unseen signal patterns. For example, an AI algorithm could identify an unknown radar signal in a dense electronic noise environment as “anomalous” and alert operators. The concept of cognitive EW (Cognitive Electronic Warfare) has also emerged in this context; systems can listen to and learn from their environment and autonomously apply the most appropriate countermeasures in real time. In the future, AI will be a game-changing factor for both friendly and enemy ELINT operations.

Case Studies and Future Projections: Recent conflict examples have clearly demonstrated ELINT’s decisive role in achieving results. In the Syrian Civil War, actors such as Russia, Türkiye, the United States, and Israel engaged in intense electronic intelligence competition. In 2018, Syrian regime air defense systems using Russian-made equipment failed to shoot down Israeli aircraft; one reason was that Israeli ELINT and electronic warfare units continuously monitored Syrian radars and exploited their vulnerabilities. During Türkiye’s Operation Spring Shield in Idlib in February 2020, the Turkish Armed Forces continuously monitored Syrian military radar and radio emissions, used KORAL to blind radars, and hunted air defense systems with UAVs. This integrated approach demonstrated that even a militarily weaker force can conduct successful offensives through superior electronic warfare. A similar scenario unfolded in the Libyan civil war: in 2020, during clashes around Tripoli, Turkish-backed forces heavily relied on electronic intelligence and jamming capabilities to neutralize Russian-made Pantsir air defense systems operated by the opposing side (Hafter’s forces). This created an electronic environment in which UAVs could operate freely. The Nagorno-Karabakh War (2020) showed the entire world how devastating the integration of ELINT and UAVs can be against conventional armored units. Azerbaijan’s forces rapidly dismantled Armenian defenses using Turkish-made UAVs and electronic warfare systems; a key factor was their ability to collect real-time intelligence and relay it to strike assets. Throughout the conflict, Turkish-provided or Turkish-directed electronic support assets detected and disabled Armenian air defense radars, while UAVs destroyed the identified targets. Consequently, traditional doctrines of warfare in Karabakh gave way to technology-centered warfare, with the integration of ELINT and UAVs becoming the key to victory. These and similar examples demonstrate that parties effectively utilizing electronic intelligence today gain significant advantages in military operations.

Looking ahead, the importance of ELINT will not diminish but will increase. Developments such as fifth-generation fighter aircraft, swarms of unmanned systems, and hypersonic missiles are making the battlefield more complex, yet detecting these systems will still rely on capturing their electromagnetic signatures. Therefore, countries are beginning to incorporate next-generation low-observable (stealth) radars, passive sensors, and AI-assisted analysis systems into their ELINT architectures. Moreover, space will become one of the most critical arenas in future ELINT competition. Strategies are being developed to protect intelligence satellites and, if necessary, neutralize those of adversaries (e.g., by disrupting satellite communications). All these trends demonstrate that electronic intelligence will remain a strategic force multiplier. As long as it remains possible to “see the unseen” through ELINT, armed forces and intelligence organizations will continue investing in this domain, striving to dominate the electromagnetic spectrum with faster, smarter, and more integrated systems.