Anti-drone systems designed to counter the UAV threat

Drones are posing an increasing threat in the battlefield as well as a threat to airports‭, ‬sports stadiums‭, ‬government buildings‭ ‬and urban areas‭, ‬therefore many companies have invested in developing anti-drone systems‭, ‬as this market is expected to increase from the current‭ $‬2‭ ‬billion dollars to‭ $‬6.6B billion by 2024‭. ‬However‭, ‬the currently developed systems are not totally capable‭ ‬of countering these threats‭, ‬thus‭, ‬a rising number of countries are deploying several detection and interdiction techniques‭. ‬

Once the preserve of the most well-resourced power‭, ‬Unmanned Aerial Vehicles‭ (‬UAVs‭) ‬or drones have become increasingly prevalent‭ ‬in many areas of life‭, ‬and are used by an increasingly wide variety of actors‭. ‬At one end of the spectrum‭, ‬the large and deadly‭ ‬systems such as Predator UAVs and their associated missile systems remain very expensive and sophisticated‭. ‬However‭, ‬the proliferation of technology and illicit support for militant and terrorist groups means such capability is spreading‭. ‬On the other end‭ ‬of the spectrum‭, ‬cheap and easily obtained small commercial drones are becoming very readily available in most localities‭. ‬

While there are obviously tremendous advantages of the development of such technology‭, ‬from defensive surveillance to media and‭ ‬logistics applications‭, ‬UAVs also pose considerable threats in a number of areas‭. ‬These include hostile surveillance‭, ‬the movement of smuggled goods‭, ‬low-sophistication terrorist attacks and general disruption‭. ‬At this end of the technology spectrum‭, ‬drones are small‭, ‬fast‭, ‬readily available in most department stores for low cost‭, ‬and difficult to detect and differentiate from legitimate UAVs‭. ‬

In terms of business opportunity‭, ‬drones offer tremendous potential and are already expanding into a number of areas of daily life‭, ‬from imagery and media at major sporting events‭, ‬to the delivery of small goods to households‭. ‬The nefarious applications of‭ ‬drones‭, ‬however‭, ‬are also offering important business opportunities for those who can develop failsafe and reliable counter-UAV‭ ‬systems‭. ‬The stakes are high‭: ‬the three-day disruption of passenger air traffic by small drones at London’s Gatwick airport in December 2018‭, ‬for example‭, ‬is estimated to have cost some airlines up to‭ ‬£15‭ ‬million in lost revenue‭. ‬Some estimates suggest the counter-UAV market has already passed‭ $‬1‭ ‬billion in value at the time of‭ ‬writing‭, ‬and is likely to expand much further‭. ‬

Techniques for countering the threat‭: ‬detection and interdiction

The challenge of countering the UAV threat can be considered broadly across two approaches and techniques‭: ‬detection‭, ‬and interdiction‭. ‬In both categories‭, ‬a number of systems are starting to emerge and are starting to show the way for the industry‭. ‬In some cases‭, ‬detecting hostile drones and steering away from them will be enough to deliver security‭, ‬while in other cases‭, ‬systems‭ ‬to promptly take such drones out of the sky will be essential‭. ‬At the same time‭, ‬both approaches are interlinked‭, ‬in the sense that effective mechanisms to remove hostile drones from the sky rely on effective approaches for detecting the drone in the first‭ ‬place and differentiating it from a friendly or legitimate drone‭. ‬

Detection approaches

Systems for detecting hostile UAVs primarily revolve around a variety of measures in which electronic signals are collected and‭ ‬monitored‭. ‬Particularly in the case of low-flying‭, ‬small drones‭, ‬traditional large-scale air defence and radar systems are not always very effective at spotting the hostile UAV in question‭. ‬With that said‭, ‬newer radar systems aimed at detecting low-altitude radio frequencies‭ (‬RF‭) ‬form the basis of many counter-UAV systems‭. ‬RF can also be used in a detection approach if the hostile‭ ‬drone is emitting data on known frequencies‭, ‬which can be monitored‭. ‬

In other systems‭, ‬heat signatures using infrared detection technology‭; ‬or audio or visual signatures using arrays of sensitive microphones or optical sensors‭, ‬whose collected data is analysed using algorithms and direction-finding triangulation‭, ‬can help to identify and differentiate hostile UAVs‭. ‬

Successful detection of hostile UAVs can allow for evasive action to be taken‭, ‬even if the UAV in question cannot be readily interdicted‭. ‬There is pressure on drone manufacturers to help by agreeing standard RFs and electronic identifiers which can be readily identified‭. ‬The Chinese AeroScope system‭, ‬for example‭, ‬offers an electronic ID platform for identifying and monitoring commercial drones using known identifiers‭. ‬Other more comprehensive approaches include DARPA’s Aerial Dragnet system‭. ‬While developed primarily for a military context‭, ‬the Dragnet concept of a network of tethered drones monitoring RFs in specific localities could be a solution for civilian environments‭. ‬Despite these developments‭, ‬some manufacturers are reluctant to surrender too much detail that could be commercially sensitive and beneficial for competitors‭. ‬

The difficulty for detection systems‭, ‬especially in the domain of smaller and lower-altitude UAVs is the effectiveness of differentiating to high levels of confidence such drones from legitimate systems‭, ‬or even from birds in some cases‭. ‬

This can obviously be a particular problem if interdiction is then undertaken against the wrong targets‭. ‬At the more sophisticated end of the spectrum‭, ‬UAVs may use complex encryption or stealth technology which can mean that electronic signatures are difficult to identify‭, ‬or are obfuscated‭. ‬In all cases‭, ‬some drones may operate largely autonomously when in flight and not emit much in the way of RF for long periods‭. ‬Generally‭, ‬it appears that there is not yet a system on the market that can offer anything‭ ‬approaching full effectiveness in accurately identifying hostile UAVs at any level‭. ‬

Interdiction approaches

Interdiction involves a range of kinetic and electronic methods for disabling a drone or taking it out of the sky altogether‭. ‬A‭ ‬number of different approaches are being trialled‭, ‬and many can be used in combination with one another‭. ‬

The traditional approach to intercepting and disabling hostile aerial vehicles is to use surface-to-air‭ (‬SAM‭) ‬or air-to-air‭ (‬AAM‭) ‬missiles‭. ‬Many of these military systems are designed to spot and interdict larger and faster vehicles than is often the case‭ ‬with UAVs‭, ‬and‭, ‬as such‭, ‬are not always very accurate to the levels required for successful interdiction‭. ‬It is also the case that missile defence systems such as the Patriot or Russian S-series systems are very expensive to deploy‭, ‬and disproportionately‭ ‬so when attempting to interdict a relatively minor UAV threat‭. ‬Nevertheless‭, ‬recent incidents such as the missile and drone attack against civilian or military institutions have highlighted the weakness of counter-UAV systems such as Patriot against low-altitude and small drones‭. ‬

As with detection systems‭, ‬many interdiction systems focus on disabling or disrupting‭ (‬“jamming”‭) ‬RF frequencies from drones‭, ‬thus either causing them to crash or disrupting their flight‭. ‬GPS‭ ‬“spoofers”‭ ‬can trick a drone into misreading its location and thus be steered away from danger‭. ‬Electro-Magnetic Pulse‭ (‬EMP‭) ‬systems fire‭ ‬high-frequency microwave signals at drones‭, ‬disrupting or in some cases destroying their electronic components‭. ‬

As with detection systems‭, ‬however‭, ‬such methods can be unreliable in accurately differentiating hostile from legitimate drones‭ ‬in the area‭. ‬In some cases‭, ‬inadvertently jamming too many drones in an area‭, ‬disrupting legitimate drones‭, ‬or causing risk to public safety through the inadvertent jamming of air traffic control‭, ‬passenger aircraft‭, ‬or civilian cellphone systems‭, ‬mean that work is still required on improving the accuracy of jamming methods in many environments‭. ‬

Other systems‭, ‬especially in more civilian environments‭, ‬have experimented with a range of nets‭, ‬laser beams‭, ‬high-velocity water jets‭, ‬“sacrificial collision”‭ ‬with deployed small drones and even well-trained birds of prey‭ (‬as used by Dutch police among others‭). ‬All of these have benefits in some cases‭, ‬primarily against smaller and slower-moving drones‭, ‬but they also have their difficulties‭. ‬

The use of any kinetic method for interdicting drones can introduce safety concerns in built-up or busy areas‭. ‬The risks can include accidentally disrupting or hitting legitimate air traffic‭, ‬or the risk of injury on the ground when a stricken drone drops‭ ‬from the sky‭. ‬Some of the net systems have attempted to mitigate this with parachutes to allow for a graceful return to earth‭, ‬such as UK company OpenWorks’s shoulder-mounted net launcher‭, ‬which uses compressed air to fire a drone-capturing net up to 100‭ ‬metres away‭. ‬

There may also be legal and regulatory issues with using kinetic interdiction methods in built-up environments‭, ‬such as questions over the rights of private companies to use such methods in public scenarios‭, ‬and insurance complications where private property is damaged or destroyed‭, ‬or where public safety is compromised‭. ‬In many cases‭, ‬such concerns are only just starting to be realised with the rapid rise of the use of small drones in urban environments‭. ‬

In general terms‭, ‬a range of approaches which integrate detection and interdiction‭, ‬and which use different mechanisms in combination‭, ‬are likely to be the favoured path for many organisations looking for effective and reliable counter-UAV capabilities‭. ‬Many of these systems are expensive‭; ‬do not always deliver high rates of reliability‭; ‬and their use in crowded‭, ‬civilian environments are posing considerable regulatory questions‭. ‬But the damage that can be done by a well-aimed UAV‭, ‬whether in physical‭, ‬reputational or cost terms‭, ‬will be increasingly severe for many organisations in such areas as critical national infrastructure‭. ‬There will be growing merit in investing in some of the emerging defensive systems on offer‭. ‬

‮»‬‭ ‬By‭: ‬Prof‭. ‬Ju lian Richards
‭(‬Centre for Security and Intelligence Studies‭ (‬BUCSIS‭), ‬University of Buckingham‭, ‬UK‭)‬

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