Beyond the horizon: protection against the artillery threat

20 September 2022

The ongoing military conflict in Ukraine has brought into sharp focus how land warfare continues to dramatically shape the direction of a war, and reiterates why ensuring an army has the technology needed to combat artillery threats remains absolutely critical.

As a result, Leonardo continues to invest significant resources into developing state-of-the-art solutions for long-range weapon-locating systems. For more than four decades, the company has delivered such technology to over 20 armies worldwide, with the Hostile Artillery LOcating (HALO) system in service with over ten nations including the British Army, Canadian Army and US Marine Corps.

HALO employs uncrewed sensor posts comprising eight or more highly sensitive acoustic sensors located 1.5-5km apart, to detect the acoustic (pressure) waves generated by gun or mortar fire and other explosive events. This allows coverage of about 2,400km2.

“When talking about artillery, we’re referring to everything from mortars upwards,” explains HALO Campaign Manager, Jeremy Stadward. “The ever-increasing threat from electronic warfare-based targeting, as well as anti-radar weapon systems countering radar-based weapon-locating systems, means demand for HALO continues to grow.

“This is because HALO passively listens for enemy artillery, without emitting an energy signature of a radar. It is able to identify the Point of Origin (POO) – where the guns were fired from – without needing eyes on the target. Therefore, armed forces can listen over the hill, in cloud and in bad weather. Having identified where those guns are, you can fire back,” adds Jeremy.

Weather and other environmental conditions, mean the action of returning enemy fire may make it difficult to hit their targets. HALO offers a clear Point of Impact (POI), allowing forces to move their guns and correct their aim, all without the enemy being aware.

The advent of HALO

Since the end of the 20th century, Leonardo has been developing and enhancing HALO. The Balkans War during the 1990s saw Muslim areas of Sarajevo shelled and many lives lost. As Sarajevo is surrounded by mountains, radars were ineffective due to ‘cresting’, whereby no energy signature is detected until the shell comes over the crest of the mountain, at which point it’s too late to react.

As a result, an Urgent Operational Requirement from the UK Ministry of Defence (MOD) led to ‘HALO One’ being deployed in around 2000, to help identify what was happening in the Balkans. Having proved its capability, several HALO systems were bought by UK MOD, with it later used in the Iraq War to identify where the Iraqi 155mm guns were.

“The longest range that we picked up guns at 155mm was 56km. It was used all the time that British troops were in Iraq to protect places like Basra Air Force Base and Basra Palace. It was operating 24 hours a day, 365 days a year, with over 98% system availability,” says Jeremy.

HALO was later deployed to Afghanistan, where it was located around Kandahar and at the former British Army airbase Camp Bastion. Additionally, the system was used by the Canadian Army near Kajaki Dam in Helmand province, to locate and ambush militants launching rockets from caves.

Adapting to the changing battlespace

As well as working as a standalone system, HALO can work very effectively as part of a system of systems, according to Campaign Manager, Kevin Cook. “In the current climate, when there’s a lot of electronic warfare out there and drones are getting knocked down, HALO is a really good broom. It is extremely versatile, which gives commanders quite an opportunity, by supporting other systems and building up the intelligence picture,” he says.

“This approach is already being taken by several armies,” adds Jeremy “with the Canadians one example of those who have HALO integrated with their command and control system”.


Looking ahead, Leonardo is now considering HALO’s role within SERPENS – the UK MOD’s next generation weapon locating programme. Campaign Manager, Rob Motherwell, says: “SERPENS is focused on replacing the Royal Artillery’s existing three standalone weapon location systems. This is not just the acoustic elements; it’s also looking at the short range and deep firing radar replacements. Now, the British Army is looking to improve them – as Leonardo is doing by investing heavily in the next generation of HALO – and integrate them with each other.”

As part of this work, Leonardo is considering how HALO would use short range and deep firing radar, as and when needed, rather than them being permanently switched on. “We would have a capability to be operational 24/7, although our big heavy radars would only be switched on for a maximum of two minutes at a time, before being redeployed to another location, so avoiding enemy fire,” says Rob.

Export opportunities for HALO also remain a priority, he adds: “While SERPENS will be a full system, we also plan to continue exporting HALO as a standalone product. Just by looking at the Ukraine situation, it is clear that there’s a real requirement to identify where artillery is coming from. As well as being of value to Eastern European countries worried about the war in Ukraine, we are also looking to export this technology to Indo-Pacific countries.”