The North Atlantic Treaty Organisation (NATO) is deepening its interest in off-board active RF (Radio Frequency) decoys to protect vessels against Anti-Ship Missiles (AShM).
NEMO trials
In November 2019 the alliance performed a series of electromagnetic operations trials off the south coast of the United Kingdom. Known as the NEMO (NATO Electromagnetic Operations) initiative, the trials are the preserve of the alliance’s Above Water Warfare Capability Group. They provide a live environment in which naval EW tactics and systems with the potential to support alliance naval operations can be trialled.
Last year’s NEMO trials involved ships from the Standing NATO Maritime Group One (SNMG1). SNMG1 includes a multinational frigate and destroyer group which is under NATO command and, in common with its SNMG2 counterpart, is tasked with an array of activities from deterrence and enhancing alliance situational awareness, to supporting exercises and operational missions.
With the ever-present AShM threat at the forefront of the minds of naval EW practitioners, Thales used the NEMO trials to perform experiments with an off-board active RF jamming capability it has developed. This employs an electronic attack system developed as part of the Anglo-French Accolade programme. This latter initiative was concluded in 2016.
The Accolade programme was commissioned to develop a manoeuvring airborne active RF decoy which could be launched from a ship. For the NEMO trials the Accolade payload was positioned onboard the company’s Halcyon Unmanned Surface Vessel (USV).
During the trials the Accolade-Halcyon combination was subjected to simulated AShM missile attacks. These were realised using land-based emitters which simulated the active radar homing seeker of an array of AShMs.
Off-board decoys
Philip Ventress, Thales’ head of electronic warfare marketing and product strategy told Armada Analysis that “there’s a lot of interest in off-board decoys, particularly in positioning a jammer close to the waterline, because that is where the threat is.”
AShMs will typically follow sea-skimming flight profiles for some of their journey, which can make them hard to detect by naval surveillance radars, and electronic support measures. These recent NEMO trials and the participation of the Accolade-Halcyon combination allowed the company to “understand the propagation efforts of RF transmission from the missile’s radar, and its reception of jamming signals from the decoy.”
Positioning a jammer close to the waterline, while potentially providing a capable means by which AShMs can be jammed when flying at such altitudes, brings its own challenges: “How do you keep a decoy stable when it is positioned on a small boat which pitches and rolls?” asked Mr. Ventress.
As the Accolade was originally an airborne system, it needed some kind of stabilisation when on the boat; a challenge which Mr. Ventress says that his team has cracked. He continued that the programme is probably at Technology Readiness Level-5. (TRL-5). According to US Department of Defence criteria TRL-5 denotes that technologies have been demonstrated in a relevant environment.
Next Steps
The company is thinking about concepts of operations for the Accolade-Halcyon ensemble. The speeds of emerging AShMs such as the rumoured hypersonic velocities of the People’s Liberation Army Navy’s new DF-100, which maybe capable of hitting speeds of 3,333 knots (6,172.7 kilometres-per-hour), could mean that simply waiting to detect such threats and then reacting could simply be too late. Instead navies may need to become imaginative about deploying EW systems to protect their vessels and task forces to pre-empt the threat: “You could have a persistent type of capability deployed.
For example, you could deploy this USV equipped with its jammer ahead of a task force or ship, oriented towards the threat,” Mr. Ventress observes: “You could communicate with the USV and update the jamming equipment with new jamming waveforms should the threat change.”
Mr. Ventress continued that the use of DRFM (Digital Radio Frequency Memory) technology within the Accolade enables the system to transmit discreet and sophisticated waveforms to confuse and seduce incoming AShM threats. Over the coming months Mr. Ventress and his colleagues plan to analyse the data they have gathered from the NEMO trial and “further study propagation and stabilisation effects.” They are also considering whether unmanned aerial vehicles could be employed with similar active RF decoys “which could be swarmed and pre-positioned around the task force. We also want to examine the potential of jamming multiple incoming threats.”
Off-board active RF jamming using USVs is an idea gaining momentum throughout NATO. As Armada Analysis reported back in its ‘Nomadic’ article in December 2019 the Royal Canadian Navy (RCN) has shown interest in such technology. To this end Rheinmetall’s Canada subsidiary and Elbit Systems is developing the Nomad active off-board jammer for the RCN.
