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The British Army has deployed a new passive counter-drone detection system at its Warminster garrison under Project Halo Shield, giving commanders a clearer picture of nearby airspace without relying on systems that actively transmit signals.

The project, led by the Army’s Experimentation and Trials Group (ETG) and funded by UK Defense Innovation (UKDI), brought together two suppliers, Dedrone by Axon and British company Quell, to move counter-uncrewed aerial system (C-UAS) technology from testing to operational use in less than six months.

During its first 17 days of live monitoring, the system recorded 29 drone position alerts, with detections reaching up to 5 kilometers away. None of the detected drones presented a threat to the base.

The Army also flew its own drones to test the system and identify possible weaknesses. The results are helping inform plans to expand passive drone detection across other British military sites.

Passive Drone Detection

Passive drone detection means finding and tracking drones without actively transmitting signals to search for them. Traditional radar systems send out radio waves and study the signals that return from objects. Other counter-drone systems may use radio frequency (RF) signals to detect communication between a drone and its operator.

A passive system, by contrast, listens to or observes the surrounding environment. It can use sensors that detect radio signals already being transmitted, cameras that identify objects in the sky, or other technologies that do not need to broadcast their own search signals.

This approach can be useful for military bases because it allows them to monitor airspace without adding another active transmitter to the area. It can also help identify drones that do not communicate through conventional RF links.

However, passive detection is not the same as drone interception. It can identify, track, and alert operators to a possible threat, but it does not automatically shoot down or disable the drone.

At Warminster, the Army is combining different passive technologies to improve detection. The system can detect drones operated by civilians, friendly forces, or potential adversaries.

Two Companies Provide a Layered Solution

UKDI supported Dedrone and Quell to provide complementary detection capabilities at the garrison.

The two companies had already worked with the Army through field demonstrations and counter-drone exercises, including Project Vanaheim and Project Flytrap. These activities helped test their technology against live drone activity and establish working relationships with the Army’s technical teams.

That earlier experience helped speed up the move from experimentation to deployment. Nick McRobb, Dedrone’s UK defense lead and a former Army Colonel, said the system was installed and operational within months of the initial demonstration.

“We moved quickly. The demonstration event took place in November 2025, and we did our on-site recce in January 2026. We were installed and operational a few months later by March 2026.”

Dedrone Uses RF Sensors

Dedrone, now part of Axon, supplied the first layer of the detection system. Its technology uses four radio frequency sensors across the garrison. Three sensors work together to triangulate the position of a drone, while a fourth sensor helps recognize and identify the drone and its controller.

The system detects signals exchanged between a drone and its operator and brings the information into a single operational picture.

This allows personnel to see where a drone may be operating and, when the available signals permit, identify the aircraft and its pilot.

RF detection is useful when a drone is communicating through detectable radio signals. However, not all drones depend on traditional RF links. Some may operate with limited communications, use different technologies, or follow flight paths that make detection more difficult. This is where the second layer of Project Halo Shield becomes important.

Quell Adds Optical Detection

British company Quell supplied its SkySpyke system as the second layer of the Warminster deployment. SkySpyke is an electro-optical counter-drone detection system designed to detect, track, and identify airborne objects. It operates autonomously and provides coverage across the sky around the base.

Unlike systems that depend on detecting communications between a drone and its operator, SkySpyke uses optical detection to observe objects directly.

This means it can help identify a drone even when the aircraft is not communicating through traditional RF signals. Quell also uses artificial intelligence to filter information and provide alerts and visual confirmation of objects of interest. This is intended to reduce the workload on operators, who would otherwise need to monitor large amounts of sensor data.

Bobby Hamilton, Quell’s Chief Operating Officer, said the system was designed to remain useful as drone technology changes.

“We’ve worked hard to build a system that is both simple and effective for the end-user. The drone threat is evolving, with a migration away from traditional RF-emitting capabilities. That’s where we can really add value. If a drone is present, we will be able to see it and identify it, regardless of how it is communicating.”

Passive Detection for Military Bases

Small drones are becoming more common in both military and civilian use. Their low cost and small size can make them difficult to detect, especially when they fly slowly at low altitude.

For military bases, an unauthorized drone may be used to observe facilities, gather information, or monitor activity. A drone does not necessarily need to carry a weapon to create a security concern.

Detection is therefore an important first step in counter-drone operations. However, finding small drones is difficult. They may appear similar to birds or other objects in the sky, while their low speed and small size can make them harder to distinguish from background activity.

AI-assisted detection can help filter these objects and provide operators with more useful alerts. Project Halo Shield combines RF and optical detection to reduce the chance that a drone will be missed because it uses a different communication method or is difficult for one sensor to identify.

The aim is to create a more reliable picture of what is happening in the airspace around a military site.

From Testing to Operational Capability

The Army’s ETG led Project Halo Shield as part of its effort to move new technology into operational use more quickly.

UKDI funding supported the deployment, while earlier Army exercises helped the suppliers improve their systems and demonstrate how they could work within military networks.

Quell’s SkySpyke had also received earlier UKDI support. That funding helped the company improve its software platform, Deep Truth, extend detection range, and redesign the hardware into a modular system.

The company later tested the system during Army exercises and operational trials, including work with Taskforce RAPSTONE, Project Vanaheim, and Project Flytrap. The Warminster deployment provided another opportunity to test the technology in a real military environment.

The first 17 days of monitoring produced 29 drone position alerts, including detections from up to 5 kilometers away. The Army also used its own drones to test the system and look for weaknesses. The results are now being used to guide future decisions on passive drone detection across the wider British defense estate.

UKDI said future phases of Project Halo Shield could see additional counter-drone systems deployed at British Army garrisons. These may include radar, RF sensors, optical systems, and acoustic sensors working together in a layered detection architecture.

Each technology has different strengths. RF sensors can help identify drones and their controllers when communications are detectable. Optical systems can observe and identify airborne objects. Radar can help detect and track objects across the airspace, while acoustic sensors may provide another way to identify drones through their sound.

Combining these systems could give military personnel a clearer and more reliable picture than relying on one sensor alone.

Col James Howard of the Experimentation & Trials Group said the project had helped improve the Army’s protection against modern threats while also developing its counter-drone capabilities.

The project demonstrates how the British Army is testing new approaches to drone detection and moving promising technologies toward wider operational use.

For now, Project Halo Shield provides the Army with a passive detection capability at Warminster. Its next challenge will be to determine how well the technology performs across different military sites, operating conditions, and drone threats.