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 owing 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.

Serious risk of collision

Since drone prices have become more affordable, drone sightings near airports have been on the increase 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.

The Drone Sighting Reports released by the United States Federal Aviation Administration (FAA) in 2016, states that there were 1,274 drone sighting reports February through September, compared to 874 for the same period in 2015. The Alliance for System Safety of UAS through Research Excellence (ASSURE) released a detailed report on November 28, 2017, stating that rigid materials allow drones to cause greater structural damage than birds of the same weight for a given impact speed. The 14-month study evaluated the potential impacts of two quadcopters and two fixed-wing drones on a single-aisle commercial transport jet and a business jet. The FAA warned about the potential threats that drones pose to airplanes and recommended that the drone manufacturers use less metal, so that drone collisions wouldn’t damage planes upon impact.

Drone chaos at airports

Commercial drones started to cause a significant amount of disturbance to 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, 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 control of Gatwick airport only after the British army deployed an Israeli-built Drone Dome defense system and the flights resumed three days later. Airport authorities indicated that the radars used for air traffic control were not effective for small UAVs and the drones can only be detected through thermal imaging systems.

To protect themselves from future incidents, both Gatwick and Heathrow airports confirmed that they have acquired and installed their own anti-drone systems. This attack by an unidentified person or persons was considered to be the most effective drone attack on an airport in recent years. In similar incidents, both New Jersey Newark International Airport and Frankfurt Airport were shut down earlier this year as a result of the disruption caused by the drone sightings. Since 2015, at least 29 major drone-related incidents occurred at airports in 17 different countries around the world.

Next tool of terror

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 the 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 as well as 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 risk 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.

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 defense systems designed to counter manned air platforms cannot provide efficient results against unmanned systems. Since air defense systems are generally designed against large aerial platforms, they could be ineffective at detecting drones with 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 threats, unlike conventional air defense 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 defense system, IMI Systems (Israeli Military Industries) product Red Sky Drone Defender system and Israeli RAFAEL Advanced Defense 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 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 to eliminate threats, such as RF jammers, Net Launchers, and GPS jamming, Spoofing. As the most commonly used method, RF Jammers neutralize the 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 the 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 the 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. According to the FAA study published on July 19, 2018, airport environments have numerous sources of potential interference which may adversely impact the safety of airport operations, air traffic control, and other air navigation services. In an airport environment, this will severely hinder the communication between the pilot and the tower, leading to potential disasters. 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.

Examples from Turkey

With the coordination of the Presidency of Defense Industries, Turkish Defense Industry companies have developed anti-drone technologies to counter the proliferated drone threat against civilian and military areas. Developed by well-renowned defense companies Aselsan, Meteksan, 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), the Aselsan IHTAR Anti-Drone System is 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 GERGEDAN Active RF Jammer System to provide protection against all known micro and mini UAV attacks. 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.

In addition, IHTAR can also be integrated with the Aselsan 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 is a new topic from 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 Defense has developed the KAPAN Anti-Drone System as a scalable solution that can handle various missions. The KAPAN Anti-Drone System offers superior drone detection and tracking performance with Retinar FAR Anti-Drone Radar, EO camera system and countermeasure systems provided by Meteksan Defense’s solution partners, such as jamming and laser weapon systems.

Unveiled at IDEF 2019, Retinar FAR is a product of Meteksan Defense’s 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. Retinar FAR is a pulse-doppler, multi-mode radar using different waveforms, which operates in Ka-Band (26.5-40 GHz) frequency. The KAPAN Anti-Drone System offers superior drone detection and tracking performance with a radar system and thermal/day cameras and allows for the elimination of 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. Retinar FAR can detect aerial targets at longer ranges (9 km) and scans 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 at far distances in 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 Defense, Selçuk Alparslan emphasized that the KAPAN system has the ability to rapidly respond to newly-emerging threats: “When we talk about airport security, though the first thing that comes to mind is the intervention of the security forces in the events that could occur inside the terminal, in fact, a greater and higher threat is the intrusions to the airport and as the result of these, the sabotage attacks that could be realized in the airport region. The increasing popularity and widespread availability of drones are causing big threat both for safety and security. Collisions with aircraft or the threat of terrorism is a subject which becomes gradually more critical for airports. The appearance of drones as a threat is a new topic from 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. KAPAN Anti Drone System consists of Retinar FAR Anti Drone Radar, camera system and countermeasure systems provided by Meteksan Defense’s solution partners, such as jamming and laser weapon systems. Retinar FAR is a product of Meteksan Defense’s 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 Defense secured the first export contract of 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 undisclosed 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 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, 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.

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 capable of detecting UAVs with a radar cross-section of 0.01m2 at ranges up to 10 km. A400 series radars use D3 (Digital Drone Detection) technology that enables them to extract the 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.

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 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. The 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 raised questions about 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 apart from 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 from civilian markets. There has been a significant increase in drone-related incidents and illegal activities that were reported over the past 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 defense 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 enough protection in the future, studies on anti-drone systems should proceed without slowing down