Taking back the sky: Counter UAS

Following our recent look at the increasing miniaturisation of unmanned aerial vehicles (UAVs), we turn this month towards some of the solutions designed to stop them in mid-flight…

The security threat posed by the misuse of commercially-available UAV technology has become a serious concern for the defence and intelligence world. A simple online search today presents a list of thousands of incidents involving improper drone flights, from near misses to crashes, with at least 3,456 such accounts being confirmed in 2016 – almost triple the number encountered in 2015.

However, as defence agencies eye this threat, ever more sophisticated technologies for countering wayward UAS (C-UAS) are being developed and matured, with many going a step beyond the conventional jamming-centric techniques that have traditionally lacked sufficient situational control and precision. When a drone is jammed, it may land in place, or it may return to its point of launch – the result is unpredictable.

SEE ALSO: This is how militaries can defend against drones

Even as technologies develop and scale-down to provide anti-jamming capabilities – including technologies designed for autonomous operations, which enjoy less dependence upon a working data link between Ground Control Station (GCS) and UAV – the longevity of jamming techniques alone is now in doubt.

Software-defined radio

The Drone Killer hand-held C-UAS device from IXI Technology was originally designed in response to wildfires that periodically ravage the forests of California. These fires are conventionally fought with water-equipped aircraft. However, when drone operators send their assets into the sky to gather imagery for surveillance and geoinformation, firefighters are forced to ground their planes and helicopters.

“In 2015, there was a major fire and the drones grounded the aircraft,” said Andy Morabe, Director of Business Development at IXI Technology.

“That wildfire went on to cause $30 million worth of damage; so developing it for first responders was the impetus for designing this technology. This project has been in the works for the last couple of years, and we’ve just got it on the market in June 2017.”

The core of the system uses a software-defined radio (SDR), and relies on less than 1 watt per channel. Rather than relying on an analogue broadband jammer, the system opts for a more accurate method. As Morabe puts it: “We don't need to be 'loud', we just need to be precise and articulate.”

"We thought the initial drone was operating on just the 5.8 GHz frequency, but then our analysis found it was actually going up five different frequencies"

A key engineering challenge of the system is the design of the antenna. The system consists of a ‘package’ of four different antennas within the man-portable device, in contrast with many existing C-UAS systems which manifest in the form of large ‘pitchforks’ of antennas with restricted mobility.

Another development focus lay in characterising the drones themselves, requiring analysis and understanding of the frequency-hopping in which small unmanned aircraft may engage. The aim of this was to write an algorithm capable of overcoming the hop.

"In a few days we characterised the algorithm and we discovered the way the frequency-hopping changes. We did an analysis on that and changed our software to adapt to it.” Said the company’s Lead Software Engineer, Bryan Ly.

“For example, we thought the initial drone was operating on just the 5.8 GHz frequency, but then our analysis found it was actually going up five different frequencies, so we followed on from that discovery.”

As Ly explained, the company would test their system by doing an initial laboratory test, and then by setting up an RF tent.

“We have a way of sniffing the frequency so we can then analyse that,” he said. “Once we’re confident that it works in the lab environment, we actually test it in the field.”

Now at a low rate of initial production, the system is currently being used by Californian law enforcement to protect sports stadiums from wayward drones, with a Lithium-Ion battery providing a 45 minute constant trigger pull, and eight hours of standby operation.

C-UAS Multicopter

Elsewhere in the growing C-UAS world, new approaches are emerging that see UAS themselves being the solution to the problem.

Delft Dynamics from the Netherlands has developed the DroneCatcher, an X-8 octocopter that fires a net equipped with a tether and a parachute to contain and safely relocate a drone operating in a sensitive area. Once captured, the DroneCatcher may carry the potentially hostile UAV to a safe place and drop it there in a careful manner by deploying the parachute. If the target is too heavy to drop safely, the parachute may be deployed immediately and the UAV can be grounded at the point of encounter.

“We’ve been working on it since its conception three years ago,” said Elwin Rath, Project Leader of Delft Dynamics. “The project is currently done for Dutch defence. A subsidy we had is ending in November, so we’re closing up the project and we’re demonstrating it now.”

The accuracy of the system in countering drones is two-fold. First, a ground-based radar system is used to provide initial detection of a potentially hostile UAS, ideally within a 2km radius, as per the current model of the overall system. As long as the data link is maintained between the GCS and the radar, DroneCatcher’s operators are able to view the location of the UAS as a waypoint on their map overlay, enabling them to click to fly their own multicopter to the area of the co-ordinates.

"After we managed to achieve continued stable flight after shooting, we then needed to continue making the netgun as compact as possible"

Once DroneCatcher is within range of the drone, the optical camera and laser rangefinder (equipped onboard the security operator’s UAS) aid in the detection, tracking, and tracing of the target, finding the optimal moment to accurately shoot the net over the drone.

UAV engineering is itself a major part of the solution. Equipping a pneumatic netgun aboard a multicopter required significant fine-tuning of the system’s autopilot in order to account for the powerful recoil experienced at the moment of firing.

“And after we managed to achieve continued stable flight after shooting, we then needed to continue making the netgun as compact as possible,” Rath noted. “That allowed us to better facilitate tilting and aiming so we could further refine its ability to catch rogue drones.”

Development of the system is ongoing, with constant collaboration between the private and public sector a crucial contributor to capability improvement. The company is currently working with the Dutch police, Dutch military police, and Dutch defence.

“It’s not always legal to take a drone out of the sky,” Rath said, “because they’re still aircraft, after all. But the parties we work with have measures that allow them to do it legally.”

RF Protocol Manipulation

Further afield, techniques are being developed that could take the principle much further than handheld mobile tools and airborne netguns.

The initial research for the MESMER Counter Drone System from Department 13 (D13) began in 2010, conducted as part of work being carried out for DARPA and the Office of the Secretary of Defense and centred around an understanding of radio protocols. The team that developed MESMER was then formed in March 2016.

Rather than any physical or operation denial-focused approach, this system is aimed at detection, identification, and mitigation of potentially hostile drones through actively controlling them.

"It's literally a matter of changing ones to zeros and zeros to ones, but it's a completely different technique to what anyone else is doing”

“We're actually manipulating the protocol of the drone,” said Jonathan Hunter, Chairman and CEO of D13.

“We're persuading the drone's radio to listen to us as a higher priority than the drone's transmitter. And then once we get control of the drone, we can actively engage in the mitigation.”

That mitigation can involve landing in place, landing in a designated area, hovering, reversing the offending system’s thrusters, or issuing any other order to which the drone’s own GCS is capable.

“We spend a lot of time figuring out the bit patterns of the protocols as that allows us to get past the encryption,” Hunter said. “At that point we can actually ‘take over’. It's literally a matter of changing ones to zeros and zeros to ones, but it's a completely different technique to what anyone else is doing.”

Similar to Drone Killer, the system is powered by an SDR, allowing continuous firmware updates on range, features and protocols. This approach also allows the development team to engage up to four drones at a time by programming data link “bouncing” behaviours towards the “circumvention of the common limitation of radio-based systems” which restrict them to interacting one-on-one in real-time.

The roadmap, as Hunter says, is focused on multiple MESMERs in a mesh network, enabling them to address an increasing number of drones simultaneously. The end goal of this is a system capable of countering and controlling a hostile drone swarm, regardless of size. This could potentially address a critical future threat that is widely known to be keeping defence strategists awake.

Choosing protocol manipulation over jamming is often considered ideal due to the degree of control that hijacking a system allows.

“Firstly, you often have no idea how long exactly it’ll take before an attempt to jam a drone will take effect,” Hunter said.

“And you need to have a close idea of the frequency, power, and range variables necessary to jam a drone in order to efficiently and effectively stop it. With protocol manipulation, however, you simply take over the drone. Those variables can be set aside so that you can directly decide the outcome.

“When you consider what could happen with a poorly-operated UAV in an urban environment with civilians around, or a hostile, IED-equipped drone in a war-torn location, you do not want to leave any space for wondering whether it’ll start descending towards homes or pavements.”

Conclusion

It is notable that many of the more advanced technologies for stopping hostile unmanned systems can be updated almost daily with software downloads. In an age of contracting defence budgets and mantras evangelising the capabilities of cost-effective systems, this is an increasingly popular model. Rather than costing billions of dollars, the C-UAS solutions with a market edge are those that can be carried on a travel laptop and uploaded within minutes to the police stations and military bases that need them.