Daniela Pistoia, corporate chief scientist, ELT Group, discusses sensors and effectors.
Small (15-150kg), mini (<15kg), micro (<66J energy state) Unmanned Aerial Systems (UAS)¹ will drastically proliferate in the near future.
Progress in power storage, avionics miniaturisation, materials and design methodologies, together with the increasing availability of commercial or open source software applications, will enable end users to broaden the range of possible uses, lawful and unlawful. The detection, identification, and neutralisation of such UAS flying near key infrastructures or sensitive areas (such as government buildings, high-profile event locations, prisons, military compounds) has therefore become a critical capability to master.
Multiple domain (electromagnetic, acoustic, electro-optic), multiple sensors (active radar, passive electromagnetic interceptors, acoustic sensors, infrared cameras), multiple jamming/deception system of systems, integrated via a dedicated command and control (C2) capability, are key elements within this approach. In addition, exploiting cyber capabilities is an important feature to factor in when addressing a mini drone-based threat.
Too small and simple to be a threat?
Drones are rapidly becoming ’tools of the trade‘ in many industries. They can be categorised into the following market segments: government (including military), enterprise (corporations/businesses) and consumers (personal/hobbyist).
Since low-altitude drones fly only hundreds of feet above ground, they mostly operate outside traditional radar coverage used to track commercial aircraft. Also military air defence radar systems are usually not designed to detect aircraft with such a small radar cross section. In other words, there is an airspace segment neither under control of civil authorities nor of military air power.
However, the use of mini drones may not be limited to zones of war or conflict. The probability of threat proliferation to domestic areas combined with the inability of traditional airspace control and defence to effectively deal with such small and low-flying objects underline even more the pressing need for appropriate counter-UAS technology.
Drone Detection and Identification
Defending a valuable asset against small UAV threats is a complex issue, since it is not only a matter of eliminating the drone to prevent it from completing its mission, but also a need to ensure the immediate detection and identification of the object prior to neutralising it in a secure framework ,as well as minimising collateral damage.
EM sensors. Defence systems may exploit the sudden presence of radio signals used to send commands from the pilot to the drone (uplink) and to send data and images from the drone to the command post (downlink). Furthermore, passive geo-location techniques can be put in place to locate both the drone and the control station.
Active/passive radar. A sensor particularly devoted to the detection of aerial tracks is the radar. However, mini drones are hard to detect and identify due to very low radar signatures (with a radar cross section of the order of 0.01m2). 3-D radars a proving to be an effective asset, sometimes used in conjunction with 2-D radars.
Infrared Sensors. Together with electromagnetic sensors, other promising devices are thermal cameras, usable under low visibility conditions and at night. Such hotspots, located in fixed positions in relation to the structure of the drone, also contribute to automatic object identification by making use of IR image reference libraries.
Acoustic Sensors. During flight, drones generate noise both in the audible frequencies and in the ultrasounds. Acoustic sensors reveal the presence of mini drones as well as help classify the target based on noise characteristics specific to the drone model. However, the operational range of acoustic sensors is limited to a few hundred metres.
Detection and identification of drones are essential, but they are only preliminary steps in solving the problem of removing the drone used for unlawful purposes. ‘Hard kill’, or physical destruction options are limited to combat zones or an open field, where the consequences of falling wreckage are minimal. In an urban scenario, a different approach aiming at a ‘soft kill’ is preferable. The following options have currently been proven as feasible and effective:
Jamming. A first option is to affect previously detected and identified radio signals, which would sever control of the drone from the operator. Then it can be forced to land in a safe area or to crash without risking collateral damage. According to the programmed modes, the drone then automatically enters into fail-safe mode causing it to land or return home. This ‘brute force’ approach however requires generating a huge amount of electromagnetic power and broad spectrum jamming of the whole area, which may also result in the undesired suppression of friendly communications. A more sophisticated and selective technique is so-called “smart jamming”, which consists of jamming the control signal only in some specific timeslots, according to the specific protocol used by the radio remote control.
GPS Spoofing. The most effective albeit complex technique is Global Positioning System (GPS) spoofing, provided the targeted UAS is using satellite navigation.² Based on military capabilities designed to deceive adversary precision guided munitions, the technique consists of first, inducing the UAV’s GPS receiver to recalculate its position and second, deviating its path in accordance with pre-planned countermeasures.
Direct Energy Weapons. In addition to these soft-kill techniques, weapons are being developed that produce a high-power microwave electromagnetic pulse which is highly effective against electronic equipment. Sensors and countermeasures need to be coordinated and integrated, so they interface via a Mobile Ad-Hoc Network (MANET) with a C2 station, typically with a man-in-the-middle, with an intuitive and easy to use interface.
Many companies worldwide are proposing solutions in this emerging field, even if a lot of Research and Development activity is still ongoing and no vendor is able to demonstrate the maturity of a ’total weapon‘. From US to Russia, including across Europe, announcements of new solutions and experimental results are published every day. Elettronica Group (ELT), the Italian EW house, is conducting trials of its solution named Anti-Drone Interception Acquisition Neutralisation (ADRIAN), which includes hacking activity against the processor on board the threat.³
In any case, every proposed solution, modular and scalable according to the operational scenarios and the needs of the final user, is several times more complex than the threat, requiring a plethora of assets deployed. Controlling these assets will require highly-qualified and best trained operators, whose mission preparation needs to be much more professional and complex compared to the relative simplicity of the threat. The costs of the defence could therefore be magnitudes higher than the cost of the attack.⁴
- According to the official NATO UAS Classification, small, mini and micro drones are subcategories of Class I. See Allied Tactical Publication ATP-18.104.22.168.1, ‘UAS Tactical Pocket Guide’. October 2016. Table 1, p.1-2.
- Miniaturisation does not only apply to UAS platforms, but also on-board electronic equipment of any kind. Size reduction does therefore not limit the use of GPS technology, as shown on the open drone market, though other methods of navigation (e.g. based on recognised terrain and objects) for small/ mini/ micro drones have been developed.
- To hack the on board processor, a strong activity of reverse engineering is needed to discover the particular vulnerability that can be exploited pending the type of processor used. Exploitation of the vulnerability will require access to the functionalities of the target via the control link. Hacking UAS is difficult but possible, proven, and effective under certain conditions.
- Counter-UAS system prices may vary between $280,000 to over $1 million (€250,000 – €1 million) depending on the specific configuration and features. A serious threat UAS may only cost between $5,000 to under $30,000.