Unmanned Aerial Vehicles (UAVs), or commonly known as drones, are aircraft without a human pilot on board. The introduction of UAVs has been one of the most significant technological advances in recent years. The capabilities and availability of UAVs are developing quickly and they now present both challenges and opportunities. Drones are now being used widely due to their availability, ease of use and low cost. While their widespread use and popularity bring benefits to certain industries, drones also pose significant risks to aviation, public security, and military operations.  As drones become more common in the skies, so too do incidents. Aircraft collisions are increasing dramatically while terrorist organizations are exploiting the accessibility that they offer.

With the Syrian Civil War, numerous state and non-state actors have had the opportunity to test new weapon systems under battlefield conditions and learn operational concepts and tactics. The current hybrid warfare environment with state proxies introduced new asymmetrical capabilities that challenge the established superiority of conventional armed forces. As an emerging threat, drones are now used by various armed groups on the battlefield where they are deployed almost daily to carry out covert and unprecedented attacks. While solutions to counter this threat are also introduced, according to the reports published by the Center for the Study of the Drone, there is a wide variance in the effectiveness and reliability of counter-drone systems. To mitigate danger from drones, a multi-pronged response is required, including appropriate rules and regulations combined with technological solutions as well as a prudential shift in law enforcement’s approach to unmanned aerial systems.

Serious Risk of Collision

Since drone prices have become more affordable, drone sightings near airports have been on the rise for years, as have the reports of drone near misses with aircraft. At least seven collisions have been reported between aircraft and drones worldwide. It has become an especially serious issue in the United States with around 100 reports per month. A majority of the incidents occur within 8 km of the airport, which is prohibited airspace for drones.

According to the Directorate General of Civil Aviation, the number of UAV pilots in our country has increased to 35 thousand, and the number of UAVs has increased to 27 thousand as of the end of last year. In just one year, 7,000 more UAVs were registered to the General Directorate of Civil Aviation (DGCA), while the number of UAV pilots increased by 13,000 with record growth. As a result of this increase in the number of UAVs and drone users, the DGCA has prepared a draft regulation that reorganizes UAV instructions. One of the most important changes in this legislative amendment is the introduction of the UAV operator definition, as in the case of airlines, so that companies that meet the necessary requirements can become UAV operators. Another important change is the removal of the definitions of uncrowded, crowded, and overcrowded areas and replacing them with green, restricted (red), permit-required, and no-fly zone definitions.

Drones Lead to Serious Airport Traffic Disruption 

Commercial drones have started to cause a significant amount of disturbance at airports in recent years. They pose an extreme safety risk to passenger jets and disrupt airports by forcing airlines to suspend flight operations. In late December 2018, the second largest airport in the UK, Gatwick Airport near London, England was shut down after three days of drone sightings. The reports caused major disruption, affecting 1,000 flights carrying approximately 140,000 passengers at an estimated cost of over £50 Million over the course of 36 hours. Authorities regained the control of Gatwick airport only after the British army deployed an Israeli-built Drone Dome defence system and the flights resumed three days later. To protect themselves from future incidents, both Gatwick and Heathrow airports confirmed that they have acquired and installed their own anti-drone systems. 

Cause for Considerable Concern

Unfortunately, drones are emerging as a cheap and effective way to deliver a variety of physical threats. It is a very well-known fact that various terrorist groups use drones during their attacks. The new drone systems have become smarter in recent years with the development of various technologies, accelerating the work on anti-drone systems. Defending civilian infrastructure differs from that of military facilities. Drones can now be pre-programmed with GPS coordinates allowing the device to automatically move to their destination without user input during flight. 

Drones are preferred by terrorist organizations due to their low cost, speed, maneuverability, payload capacity, and risk-free advantages. They have become a serious threat for critical plants such as nuclear power plants, stadiums or airports. Although there hasn’t been a tragic incident so far, the fact that drones strengthen the psychological effects of terrorism makes the issue even more sensitive. As the popularity of drones increase, it will be easier to obtain them, causing greater risks to both safety and security. The widespread availability of drones and the potential danger of this situation is one of the most important reasons for the development of anti-drone systems.

In Syria and Iraq, the ISIS terrorist organization operated a wide variety of drones to carry out coordinated attacks. ISIS’ ability to operate small UAVs dramatically changed the balance of capabilities between the terrorist group and the U.S. led Coalition forces. In October 2016 the terrorist group used unmanned aerial systems armed with explosive ordnance to conduct numerous attacks against tactical and strategically important targets by dropping grenades and small bombs on groups of soldiers, vehicles, and buildings. The group carried out more than 200 such attacks in 2017 alone. Parallel to the developments in UAV systems, ISIS also used drones at the tactical and operational level to provide reconnaissance-surveillance-intelligence and to guide their militants and vehicle-borne IEDs (SVBIED) more accurately toward their targets.

Related to the ongoing conflicts in Syria, on 5-6 January 2018 Al-Nusra Front militants carried out a drone swarm attack against Khmeimim and Tartus bases used by the Russian Federation Armed Forces. As the first of this kind in the history of warfare, this particular attack was quite significant as it demonstrated the threat level that UAVs can easily reach. According to the statement by the Russian Ministry of Defence, 13 fixed-wing drones, each armed with ten pieces of improvised explosive devices (IED) weighing approximately 400 grams, were involved in the attack. The effective radius of the ordnance was stated to be 50m. Militants targeted the Khmeimim Air Base with 10 UAVs and Tartus Naval Base with 3 UAVs. It was also reported that another UAV equipped with camera systems was also used for damage assessments and firing adjustments. The presence of a surveillance drone may indicate the tactical command-control capabilities of the militants in coordinating the drone attack in real-time. Head of the Russian General Staff’s Office for UAV Development Major General Alexander NOVIKOV stated that six of 13 drones had been neutralized by electronic warfare systems and the remaining seven were shot down by the Pantsir S-2 air defence system. The improved version of the earlier Pantsir S-1, Pantsir S-2 is armed with two very high rate-of-fire 2A38M 30mm automatic anti-aircraft guns derived from the GSh-30 twin-barrel 30mm aircraft-mounted cannon. The Pantsir S-2 also carries the new highly capable 57E6-E guided surface to air missile.

Since 2015, Yemen’s government has been in a civil war against the Houthi movement that originated in Northern Yemen. Part of a larger regional conflict between Saudi Arabia and Iran, this controversial conflict has caused considerable casualties and a famine that’s killed an estimated 50,000 people. The US government has also been involved in the conflict, supplying weapons to the Saudi-led coalition against the Houthi rebels. The Iran-aligned Houthis have launched a series of drone attacks since early 2018. In July, Houthis carried out an attack against Saudi Aramco oil refinery in Riyadh with armed drones and another one against the international airport in the UAE. On January 10, 2019, the Iranian-backed group conducted a targeted attack with a bomb-laden drone, killing at least 6 members of the Saudi-backed Yemeni forces gathered at an army parade near the al-Anad airbase, including a number of senior Yemeni military officers as well as military intelligence head Maj. Gen. Mohammad Saleh TAMAH.

The most important factor in Houthi drone attacks is that these actions have a versatile and holistic profile. Considering the Iranian connection, the use of drones by these irregular forces can be considered as part of the proxy war concept. The ballistic missile attacks adopted by the Houthi militants with the possible technical assistance of Iran have had devastating results for the Saudi-led Coalition, causing more than 100 casualties. Within this context, the Houthis launched a series of drone strikes against MIM-104 Patriot PAC-3 air defence systems located in the central Yemeni province of Ma’rib in February 2018 with Qasef-1 drones, and the Najran Regional Airport in southern Saudi Arabia in May 2019 using Qasef-2K drones. According to a report of the Conflict Armament Research (CAR) group, the Qasef family of drones are near-identical copies of the Iranian-made Ababil-2 UAVs which can carry a 30kg warhead.

In summary, the acquisition of UAV capabilities of non-state actors is a serious matter that needs to be addressed in the very near future. Because terrorist organizations employ the majority of their platforms in a kamikaze type of attack, it is critical to prevent these organizations from establishing a supply chain that is essential for operational continuity. Furthermore, not relying on a single system and using combined elements such as electronic warfare and various air defence systems together, to counter the drone threat as in the case of the Russian approach against the drone swarm attacks, will become increasingly important.

Countering the Threat

The number of anti-drone systems has increased dramatically in recent years as a result of drone-related threats against critical facilities and civil aviation. Conventional air defence systems designed to counter manned air platforms cannot provide efficient results against unmanned systems. Since air defence systems are generally designed against large aerial platforms, they could be ineffective at detecting drones with a much smaller radar cross-section (RCS) at long distances. Furthermore, developing low-cost solutions is one of the most important requirements when designing dedicated systems to counter UAV threat, unlike conventional air defence systems.

According to the CSD Counter Drone Systems Report published by the Center for the Study of the Drone at Bard College in February 2018, there are currently 235 anti-drone solutions sold by 155 companies from 33 different countries. The AUDS consortium (Blighter Surveillance Systems, Chess Dynamics and Enterprise Control Systems) product counter-UAS defence system, IMI Systems (Israeli Military Industries) product Red Sky Drone Defender system and Israeli RAFAEL Advanced Defence Systems product Drone Dome system which was reportedly used at Gatwick Airport, are among the most capable anti-UAV systems available worldwide.

The development of anti-UAV systems is directly related to the characteristics of the areas where such systems will be used. In residential areas and metropolises, anti-UAV systems are frequently used to protect centers with a high concentration of civilians and critical facilities against terrorist threats. Anti-UAV systems to be used in rural areas and residential areas can have significant differences between them. This situation creates numerous challenges for the use of these systems in important locations with a potential threat.

Anti-drone systems utilize different types of technologies such as Radar, RF Scanners, Acoustic Sensors, and Electro-Optical Thermal/IR Cameras to detect mini and micro UAVs. Anti-Drone systems employ radars as their primary detection technology. Special radars capable of operating in all weather conditions are used to detect low-flying UAVs and differentiate them from other aerial platforms and birds. 

As a passive detection method, RF scanners can detect drones by scanning their frequency bands. The operating principle of RF scanners is similar to that of radars but differs from them by using passive detection technology. Anti-drone systems can also be integrated with acoustic sensors that can detect drones from engine and propeller noise. To identify and classify drones detected by these active (Radar) or passive (RF, acoustic) techniques, anti-drone systems use electro-optical camera systems that can detect UAVs with day/night or infrared (IR) sensors. Since the technologies alone are not effective in detecting all different types of UAV threats as standalone systems, existing anti-drone systems use these methods in an integrated way. Moreover, artificial intelligence can also be used for the identification and classification of UAVs. 

Anti-drone systems use a combination of different techniques which can be grouped as kinetic and non-kinetic to eliminate threats. Non-kinetic solutions intercept the drones without directly damaging the device by interfering with the communications signals that drones rely on for guidance and control. Non-kinetic solutions include technologies such as RF jammers, GPS jamming, and Spoofing. As the most commonly used method, RF Jammers neutralize UAVs by disrupting their radio transmission or satellite communication signals used for navigation. The disconnected drones either proceed to land on their current position or return to their take-off point. RF Jammers are also capable of blocking the audio and video feed transmitted from UAVs. However, this method is ineffective against autonomous systems as they do not rely on a permanent connection with their users. Along with GPS jamming and Spoofing, RF jamming is the most widely used method by anti-drone systems today. GPS jamming refers to deceiving GPS-capable devices by broadcasting false GPS signals relaying incorrect geo-location coordinates. Spoofing, also known as protocol manipulation, is used against UAVs to take control of the targeted drones by hijacking their command-control or satellite/navigation communication.

However, one major drawback of RF jammers is the level of precision required to jam drone signals while not interfering with other frequencies. RF jammers must be continuously pointed at the drones to work as intended. Another problem is, RF jammers cannot counter specific radio signals but a range of frequencies (typically from 2.4 to 5.0 MHZ) which means that any communication device operating in the jammer’s frequency range would also be disrupted.

Kinetic solutions or commonly known as “hard kill” measures use physical force to neutralize and render drones inoperable. One of the primary advantages of kinetic solutions is that they work against UAVs, which follow pre-programmed GPS coordinates without relying on RF, WiFi, or other communication protocols. The most prominent methods for countering UAVs with kinetic capabilities include projectiles, rockets, and laser systems. Certain anti-drone systems such as the AUDS consortium Counter-UAS Defence System (Kongsberg XM-153 CROWS II M134 Weapon Adapter Kit) or the Aselsan IHTAR Anti-Drone System (Aselsan SARP RWS fitted with 40 mm MK19 Mod3 AGL using ATOM Air Burst Munition) can be combined with Remote Controlled Weapon Stations to provide a high-volume of destructive firepower against UAVs. Although this method is generally considered more primitive, it provides better results than other solutions. Recently, anti-drone system producers have also started to demonstrate their solutions to neutralize drones with laser weapons. The U.S. defence giants Raytheon and Boeing, as well as German Rheinmetall and MBDA Deutschland have been heavily investing in directed energy weapon systems. All the companies are currently developing High Energy Laser (HEL) weapon systems against aerial threats, including UAVs. Turkish defence industry companies Aselsan (LSS - Laser Defence System) and Roketsan (ALKA YESS) have also introduced their own directed energy systems. Lasers are considered as part of kinetic interdiction methods because they directly damage or destroy drones. Directed energy weapons have become the preferred choice of militaries around the world for future implementations as this capability can be especially effective against small, fast, and agile UAVs. The most obvious disadvantage of kinetic counter-drone solutions is that they pose a significant risk of collateral damage. Kinetic solutions rely on physically damaging or disabling drones and rendering them inoperable. Once a drone is knocked out of the sky, it simply falls down endangering people or critical infrastructure that may happen to be below it. Therefore, using kinetic solutions in heavily populated areas or sensitive facilities creates a serious safety risk.

Another method that Anti-Drone systems employ against UAVs is to disable their propellers by using nets. The nets can be carried by another drone or launched from different devices. This particular method was first used in April 2015, in Japan to catch a rogue drone that landed on the roof of the Prime Minister’s office while carrying small traces of radioactive material in protest against the government’s nuclear energy policies. In a unique approach, Dutch company “Guard from Above” trains eagles to intercept rogue drones. The large birds of prey wear protective shin-guards to protect their legs from the drone’s rotors. According to the company’s statement, the natural predators trained by certified bird handlers have a 95% intercept rate. The stated success rate is currently higher than many ballistic kinetic solutions.

Examples from Turkey

With the coordination of the Presidency of Defense Industries (SSB), Turkish Defence Industry companies have developed anti-drone technologies to counter the proliferated drone threat against civilian and military areas. Developed by well-renowned defence companies Aselsan, Meteksan Defence, and SDT respectively, the anti-drone systems are designed to protect critical facilities by neutralizing potential Unmanned Aerial Vehicles (UAVs) threats with their integrated RF Jammer capabilities and optional hard-kill features.

Aselsan IHTAR Anti-Drone System

Developed in co-operation with the Turkish Armed Forces and the Presidency of the Defense Industries (SSB), Aselsan IHTAR Anti-Drone System designed to counter mini and micro UAV threats in urban and rural environments. The system is used to protect critical military and commercial sites from Micro/Mini UAV threats. The IHTAR system consists of a Radar and Electro-Optical sensor, RF Countermeasure, Tactical Signal Emulator and Command Control system. In order to utilize the most effective countermeasure in terms of efficiency and security, Aselsan’s IHTAR system provides an integrated and coordinated operation of Radar, Electro-Optical sensor, and RF Jammer with command and control capabilities. The system can be operated in mobile of fixed configuration. 

IHTAR uses the Advanced Capability Aselsan Radar (ACAR) as its primary surveillance sensor. It is a solid-state pulse-doppler radar which operates in Ku-Band (12.5-18 GHz) frequency. ACAR uses a mechanically scanned antenna with selectable rotation speed. The highly accurate radar can scan 360° or a specific sector with adjustable sector width. It can track multiple targets automatically and has a track-while-scan capability in surveillance mode. The radar can also detect mini-UAVs with a radar cross-section of 0.5 m² at 5 km. ACAR is used together with an E/O imaging system with both thermal and daylight cameras. This is used for the identification of targets once they have been detected by the radar.

As the primary countermeasure, IHTAR uses the GERGEDAN Active RF Jammer System to provide protection against all known micro and mini UAV attacks. The GERGEDAN system covers all frequency bands and provides simultaneous jamming capability against Remote Control (RC) Devices, Radios (PMR and FRS), GPS receivers, WLAN Applications, ISM Bands, GSM 900, DCS 1800, 3G and 4G. The system also provides directional jamming against specific threats and omnidirectional jamming against swarm attacks with its specially designed antenna creating a semi-spherical protection umbrella. 

The IHTAR Anti-Drone System can be combined with jammers, laser, and a 40mm grenade launcher according to the requirements of the customers to provide both soft-kill and hard-kill capabilities. While the RF Jammer is the preferred system to be used in urban areas, the 40mm grenade launcher can be used in critical sites with open fields if needed. As part of the development, the integration of the 40mm grenade launcher into the system is still underway and is expected to be completed within the next year. The IHTAR Anti-Drone System can be operated both manually and automatically and requires only a single crew member. The system incorporates automation and elements of machine learning designed to ensure that the system can counter future threats. IHTAR is customizable with its open and modular architecture which enables integration of different radar and countermeasures into the system.

In addition, IHTAR can also be integrated with Aselsan’s CHAMELEON Tactical Signal Emulator to take control of drones by emulating the signals of the RF controller. CHAMELEON can be used as an arbitrary waveform generator or programmable noise generator. It can generate both Electronic Warfare (EW) waveforms and civilian communication waveforms with a single waveform generator.

Meteksan KAPAN Anti-Drone System

The appearance of drones as a threat has become a new topic over the past few years, and there are discussions worldwide about what may be the most effective solution to this threat. There are several aspects to this issue, all of which need to be addressed separately. Meteksan Defence has developed the KAPAN Anti-Drone System as a scalable solution that can handle various missions. KAPAN Anti-Drone System offers superior drone detection and tracking performance with the Retinar FAR Anti-Drone Radar, EO camera system and countermeasure systems provided by Meteksan Defence’s solution partners, such as jamming and laser weapon systems. 

Unveiled at IDEF 2019, the Retinar FAR is a Meteksan Defence product that provides in-depth analyses and rigorous field tests regarding drone detection. This version of the Retinar fields a new antenna that has been designed specifically for the surveillance of air space and for the detection of drones with high-performance hardware and special algorithms. The Retinar FAR is a pulse-doppler, multi-mode radar using different waveforms, which operates in multi-mode Ka/Ku-Band (26.5-40 GHz/12.5-18 GHz) frequency. The KAPAN Anti-Drone System offers superior drone detection and tracking performance with a radar system and thermal/day cameras and eliminates drones with an RF jammer and an optional laser system. Different systems have been appropriately integrated into the KAPAN Anti-Drone System with standard interfaces and scalable architectures to create an effective solution against drone threats in different situations and scenarios. The Retinar FAR can detect aerial targets at longer ranges (9 km) and scan a broader area (40°), thus turning KAPAN into a more potent drone hunter. 

The KAPAN Anti-Drone System is capable of classifying and identifying targets in far distances with low visibility conditions where detection with camera systems is difficult. The highly flexible system can be used on a stationary position or on a vehicle thanks to its single-axis integration and single point connectivity features. The KAPAN Anti-Drone System provides continuous 360° coverage as well as angular surveillance in selected sectors with alarm zone management. Designed to be functional against swarm UAVs, the system can be integrated into existing security systems and reduce unwanted electromagnetic interference with directional jamming.

Furthermore, a Laser Countermeasure System can also be integrated into the KAPAN Anti-Drone System as an optional feature to provide hard-kill capability when requested. The system is capable of destroying and neutralizing drones at 500m with a high-power laser emitter located on the optical tracking and guidance unit. The E/O unit is mounted on a stabilized 3-axis gimbal for precise orientation, and it consists of a SWIR camera, MWIR camera, daylight camera, laser rangefinder, laser optics, GPS, magnetic compass, and image processing sub-units.

President of Meteksan Defence, Selçuk ALPARSLAN emphasized that the KAPAN system has the ability to rapidly respond to newly-emerging threats: “The appearance of drones as a threat is a new topic over the past few years, and there are discussions worldwide about what may be the most effective solution to this threat. There are many aspects to this issue, all of which need to be addressed separately. We have developed the KAPAN Anti-Drone System as a scalable solution that can handle various missions. The KAPAN Anti Drone System consists of the Retinar FAR Anti Drone Radar, camera system and countermeasure systems provided by Meteksan Defence’s solution partners, such as jamming and laser weapon systems. The Retinar FAR is a Meteksan Defence product that provides in-depth analyses and rigorous field tests regarding drone detection. This version of the Retinar fields a new antenna that has been designed specifically for the surveillance of air space and for the detection of drones with high-performance hardware and special algorithms.” 

In the last quarter of 2017, Meteksan Defence secured the first export contract for the Retinar PTR with an undisclosed country. The company scored its second export success on July 12, 2018, with the Retinar PTR-X, an improved version of the PTR Radar. The system was selected as the perimeter surveillance system of an unnamed airport in the capital of a European country, and it has been in use ever since.

SDT AVCI Anti-Drone System

The SDT AVCI Anti-Drone System is designed to detect, track and defeat Micro and Mini Unmanned Aerial Vehicles (UAVs) and Unmanned Aircraft Systems (UAS) engaged in hostile airborne surveillance and potentially hostile activity. SDT developed the AVCI system to meet the specific requirements of the Turkish Armed Forces and security forces. AVCI is a smart-sensor and countermeasure package capable of remotely detecting small UAVs and then tracking and classifying them before providing the option to disrupt their activity. The thermal cameras on the system are provided by the Turkish company Mikro-Tasarım. The system combines electronic-scanning radar target detection, electro-optical (EO) tracking/classification and directional RF jamming capability. Unlike other similar Turkish systems that use mechanically scanned radars, the AVCI system employs PESA (Passive Electronically Scanned Array) radars produced by UK based Blighter Surveillance Systems. During IDEF 2019, SDT signed an agreement with Blighter to locally produce the radars.

The AVCI Anti-Drone System uses A400 Series Radars which operate in Ku-band frequency. The radar is a modular non-rotating, electronic-scanning (e-scan) system using power efficient PESA (passive electronically scanned array) and FMCW (frequency modulated continuous wave) technologies to provide reliable, Micro and Mini UAV detection in all-weather conditions. It is able to detect UAVs with a radar cross-section of 0.01m2 at ranges up to 10 km. The A400 series radars use D3 (Digital Drone Detection) technology that enables them to extract tiny radar reflections from modern plastic bodied UAVs even when flying close to the ground or near buildings where clutter reflections are relatively large. The radar covers 180° and can be used in back-to-back configuration to provide 360° surveillance. Target tracking software and extensive zone filtering features allow drones to be detected while reducing false alarms from birds. 

The AVCI system weighs around 350kg and SDT is currently working on a lighter version of the system to be used on military surveillance vehicles. The system may be used in remote or urban areas to prevent UAVs from being used for attacks or malicious activities against sites with critical infrastructure. The SDT AVCI Anti-Drone System can use various sensor subsystem configurations based on requirements. Detected drones can be defeated using directional/omnidirectional jamming solutions or hard-kill solutions. 

Although these indigenous counter UAV systems were designed and developed to primarily protect military bases and critical facilities, the growing interest in commercial unmanned systems and the changing threat environment by extension, created a need for the use of these systems in civilian environments. Ever since the drone-related incidents, and the questions that arose regarding the security of crowded places, counter-drone systems began to appear at various events and risky locations such as airports, stadiums, and convention centers with increasing regularity. Regarding the recent incidents, the growing demand for anti-drone systems from outside the military domain is expected to play an important role in accelerating the efforts to develop more integrated and cost-effective solutions in the coming years. 

Conclusion

The need for anti-drone systems has once again been revealed with the increasing number of illegal activities carried out with drones, which are now easily accessible in the civilian market. There has been a significant increase in drone-related incidents and illegal activities reported over recent years. It is clear that drones can be used for malicious intent, and this will pose a far greater threat in the future with the advancement of technology. Thus, it is highly essential to introduce the necessary regulations and establish a nationwide multi-layer defence network against UAV threats for the protection of critical facilities. Preventing the use of UAVs by terrorist and criminal organizations for the national security of our country is also another issue that should be taken into consideration. Considering the new developments in UAV technology and the possibility that today’s anti-drone systems would not provide sufficient protection in the future, studies on anti-drone systems should proceed without slowing down