Leonardo UK has been awarded a £18.3 million contract to supply its SONUS acoustic artillery locating system to the British Army’s Royal Artillery. Leonardo’s system will replace the old Hostile Artillery LOcating (HALO) sets currently in use, under the Passive segment of the wider Project SERPENS, which is intended to renew and expand the entire line of weapon locating sensors of the Royal Artillery.

According to the Ministry’s press release, the project will sustain 250 jobs across the UK, mostly at Leonardo’s Basildon site, but also through “29 small and medium sized enterprises (SMEs)” involved as suppliers.

It is also claimed that SERPENS Passive is being delivered “5 years earlier than planned”, but this claim is dubious: at the time of the invitation to tender in February 2025, contract award had been indicated for September 2025, with duration to 2030. That plan probably envisioned slower deliveries, but the Ministry appears to be particularly indulgent with itself.

In earlier phases of the project, it had been indicated that the new passive sensors were to integrate an optical element as well as the acoustic segment, but at the moment it’s impossible to say if this is still the case. SONUS as a system is purely acoustic.  Leonardo states that SONUS can identify acoustic pressure waves produced by gunfire, mortars, and explosions, allowing operators to pinpoint both where the sound originated and where it landed with the help of advanced acoustic processing technology.

SONUS has a reduced power consumption allowing it to operate longer in the field, with less need for resupply. The sensor posts use integrated GPS microphones, enabling deployment in under 3 minutes, reducing the risk of exposure to soldiers operating in hostile territory.

SONUS is the latest evolution of the HALO line of acoustic sensors and comes in a lighter and easier to deploy format: it is said to be 50% smaller in volumes and 70% lighter than its predecessor.

An unspecified number of SONUS kits will be delivered to 5 Regiment Royal Artillery, the Surveillance and Target Acquisition specialized regiment of the British Army, over the coming 12 months. SERPENS is also due to deliver a new Command and Control system to bring all its components together and is due to deliver 2 different sizes and types of radars, one Deep Find and one Close Find.

In 2023 the British Army had identified the Thales GM200 as its Deep Find solution, anticipating a joint procurement with the Netherlands, but the British order has yet to be firmed up. The UK is shown as having joined the NATO Support and Procurement Agency’s project for the GROUNDMASTER family of radars, however.

SERPENS Close Find’s selection process was launched early in 2025 with plans for the acquisition of 25 radars using a competitive flexible procedure under a staged delivery schedule to complete during calendar year 2027. Deliveries of the radars were to happen over a 2-year period, followed by an initial 4 years of in-service support. Contract start was envisaged for 29 May 2026 but, as for all other British defence programs, uncertainty rules supreme.

FOXHOUND armoured 4x4 vehicles were indicated as the intended platform to ensure SERPENS Close Find mobility on the battlefield. This too cannot be taken as a certainty, however.

At present, the Royal Artillery fields just 5 TAIPAN counter-battery radars, aka SAAB ARTHUR D systems. TAIPAN was obtained through a Mid Life Upgrade project from the earlier ARTHUR C sets (MAMBA in British service). While MAMBA was installed on BV206 all-terrain articulated vehicles, TAIPAN uses a shelter carried for mobility on MAN SV 9-tonne 6x6 trucks.

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