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Intelligence, surveillance, and reconnaissance (ISR) capabilities are an essential, overlaying enabler for naval operations. As the strategic importance of operational tasks such as mine warfare and anti-submarine warfare returns, so does the requirement to expand and enhance ISR capability and its support for such tasks, particularly through enhancing multi-domain command, control, and communications.

Intelligence, surveillance, and reconnaissance (ISR) is a multi-domain activity. In the maritime domain, assets are deployed in the air, on and below the surface – as well as ashore, in coastal, littoral regions – to conduct ISR tasks, to enhance maritime situational awareness (MSA) and contribute to the development of a common operating picture.
Against the backdrop of returning naval rivalry at sea, crewed platforms are increasingly required to apply their ‘exquisite’ capabilities to higher-end operational tasking, and/or where human operator decision-making remains paramount. With crewed platform numbers still limited across many Western navies, a consequence of this shift in focus back towards high-end activity for crewed platforms is that there is a pressing operational requirement emerging to bring maritime uncrewed systems (MUS) into service sooner rather than later.

In the near term, while navies’ confidence in MUS technology and capability continues to develop, MUS are being introduced to meet two overlapping requirements. The first is to provide mass in terms of assets deployed at sea. The second is to support what are known as the ‘3-D’ operational tasks – tasks that are ‘dull, dirty, or dangerous’. Such ‘dull’ and ‘dangerous’ tasks encompass ISR requirements as part of building MSA. Here, certain ‘dull’ and ‘dangerous’ tasks require MUS to provide sustained ISR capability, often at a fair distance from any host platform. Such tasks include providing sensing capability for anti-submarine warfare (ASW) barriers, or for sanitising (also known as ‘de-lousing’) deployment routes for high-value assets using mine counter-measures (MCM) operations.

For NATO navies, the current strategic-level naval rivalry evident at sea across the Euro-Atlantic theatre has heightened the operational focus on core high-end tasks, including ASW, amphibious operations, and MCM, with each of these tasks enabled by ISR.

A Light Autonomous Underwater Vehicle (LAUV) used for seabed scanning is pictured being operated by Royal Danish Navy (RDN) sailors at the ‘REPMUS’/‘Dynamic Messenger’ exercise. The RDN also deployed an AUV – a Teledyne Gavia system – to conduct over-the-horizon MCM ISR.
Credit: NATO Maritime Command

Russian submarine activity has increased across the theatre, but is particularly significant in Northern Europe and the Eastern Mediterranean. The risk of the Russo-Ukraine war spilling over has sharpened NATO’s naval focus on amphibious operations in the Baltic Sea (to secure the Baltic States) and along NATO’s northern flank (to deter any risks to Norwegian security). As regards MCM, the strategic importance of the Black Sea in the Russo-Ukraine war has seen the deployment of significant numbers of mines to support defensive and offensive operations across the regions, with such mines – including those now drifting, after becoming detached from their mooring lines – posing a significant risk to commercial shipping.

Exercise Focus

All these matters have been very much the focus for the Portuguese Navy-led ‘Robotic Experimentation and Prototyping augmented by Maritime Unmanned Systems’ (REPMUS) and the NATO Allied Maritime Command (MARCOM)-led ‘Dynamic Messenger’ exercises, which took place in tandem at Troia, southern Portugal across September. The core remit for both exercises is to focus almost exclusively on testing and evaluating MUS systems in operational experimentation that is designed to reflect ‘real-world’ requirements as closely as possible.

The serials around which the exercises were based were designed to reflect such ‘real-world’ operational requirements for NATO. During the activities, the four primary areas of operational focus were ASW, underwater operations (including the protection of critical underwater infrastructure [CUI]), MCM, and rapid environmental assessment. Effective ISR – either at an overall or an event-specific level – is vital as an enabling capability in all four contexts.

Overlaying these four areas of tactical-level focus, a core operational-level goal for the exercises was to develop multi-domain command, control, and communications (C3) capability. Developing effective multi-domain C3 capability will be essential in underpinning NATO tactical operations at sea, with ISR helping to build the MSA layer that is central to constructing this C3 capability. Together, this develops the integrated capability that enables effective delivery of core operational tasks such as MCM and ASW.

For example, in ‘REPMUS 2023’, which took place across the first three weeks of September, one of the serials tested – for the first time in a ‘REPMUS’ exercise – the use of an uncrewed underwater vehicle (UUV) in conducting over-the-horizon ISR to support an MCM operation in advance of an amphibious assault ashore.

An over-the-horizon mission was undertaken because it was the first time that a UUV with the required ‘legs’ (range and sustainability on station) had been deployed on ‘REPMUS’. The UUV was a Teledyne Gavia autonomous underwater vehicle (AUV), brought to the exercise by the Royal Danish Navy. While the serial was designed to prove that the AUV could sustain operations over the required distance and timeframe, it was also designed to demonstrate that the required level of autonomy could be generated for the AUV to ensure effective conduct of the core mission deliverables.

Operational Requirement

According to a NATO briefing document published online in May 2023, ISR “provides the foundation for all military operations”. In the document, NATO defined surveillance broadly as the persistent monitoring of a target, reconnaissance as information-gathering to address a specific military task, and intelligence as the final, fused product derived from combining – together with other forms of information – the surveillance and reconnaissance data collected.

For the exercise serial, over-the-horizon MCM operations using a UUV were required to provide discreet capability to support an amphibious operation, a NATO military official told a media briefing at ‘REPMUS’, held at the MCM operations ‘hub’ in Sesimbra, west of Troia. As amphibious operations are often launched from the sea at some distance from shore, from a task group remaining out of range of littoral defences, UUVs are playing an increasingly crucial role in providing ISR to conduct and support MCM activities, in large part because using crewed platforms for the MCM task would indicate the looming presence of the amphibious force.

The exercise serials were designed to support development of how NATO and its navies will conduct MCM operations in the future, bringing “unprecedented change in the way we are doing mine warfare”, the NATO official said. This change includes the introduction of a broader variety of systems including uncrewed vehicles, the use of a mix between crewed and uncrewed platforms, increased sensing capacity introduced via the uncrewed platforms, and improved analysis, distribution, and tactical use of the greater data volumes being generated by those sensors.

This new approach adds another layer of complexity to what, in MCM, is already a challenging operational task. “That’s why we need experimentation … to improve our procedures and tactics,” said the NATO official.

The UUV was deployed from Sesimbra, and sailed east to the location of the planned amphibious assault, off the Troia peninsula. The UUV conducted a scan of the seabed within the operating area, with this mapping supporting identification of any suspected mine-like contacts, the NATO military official explained.

UUVs were deployed on ‘REPMUS’/‘Dynamic Messenger’ to provide ISR imagery of what could be detected on the seabed, including mines and other objects. For example, French Navy and UK Royal Navy systems (France’s Alister9 UUV is pictured) collaborated to share, compare, and contrast imagery and information gathered.
Credit: NATO Maritime Command

Real-World Relevance

In real-world operations, forward-deployed UUVs can conduct discreet ISR and MCM without revealing their presence, by deploying from a host platform over the horizon, conducting a covert transit, undertaking tasking with reduced risk of detection due to their covert operation and smaller size, and initiating timed destruction of any mine-like objects identified by fixing a delayed-fuse charge to any mine target positively identified.

The mission aim in the exercise serial was “to practice …. objectives with regard to specific scenarios. So, long-range [ISR and MCM operations] were tested in the view of conducting covert operations for the specific requirements of amphibious assault,” the NATO official said. “If you want to do it covertly, your vehicle needs to be deployed far away and transit underwater [from where] it is safe, over the horizon.” The UUV was deployed from shore for the exercise, the official continued, but it could also be deployed from a ship that would approach the landing area, but stand off at distance over the horizon to avoid detection and observation.

“The idea was to conduct a bottom-mapping scan of the seabed in the landing corridor, without showing the ongoing efforts prior to the landing,” the NATO military official said. “So, with uncrewed systems, or UUVs, this becomes more possible because, if they transit underwater, you will not be able to spot them from the landing beach.”

“The mission profile was planned so that the vehicle would dive off Sesimbra, make a full transit underwater in a completely covert manner, arrive in the amphibious corridor, and do some tracks to do some bottom mapping. Still underwater, it would transit back to Sesimbra, surface, and then [be] recovered,” the official continued. “The mission data was downloaded … and some post-mission analysis software was run in order to classify bottom objects. Some of them were classified as mine-like contacts. So, that means you have an idea of the small objects on the bottom which potentially could be mines.”

CMRE’s Biondo AUV is pictured during a ‘REPMUS’ demonstration serial conducting bottom mapping surveillance work. Such ISR tasking is key to supporting MCM and CUI operations.
Credit: Dr Lee Willett

Such information is then used to inform planning for the amphibious operation. “Either you adjust your route to avoid those possible mines, or you go … back there to identify and to determine if the possible mines are actual mines or not,” said the official.

In this exercise serial, planners then deployed an MCM vessel to the landing corridor, with explosive ordnance divers used to reacquire and formally identify the possible mines classified by the UUV.

For the exercise, 24 dummy mines were deployed off Sesimbra and 21 off Troia, to test the ability of the assembled operational units to detect seabed mines or moored mines. Three more were deployed in the landing corridor for the amphibious serial.

The purpose of the ISR work and the post-mission analysis was to understand how many mine-like contacts had been located, and how many had been classified as actual mines, the official said.

“The aim is to be very accurate in our ability to classify, because if we have too many mine-like contacts, if you want to identify them to be sure of the nature of the contact, it will be a cumbersome task because it takes time; or if we want to divert the traffic to where there are no mine-like contacts, there are mine-like contacts everywhere and it’s impossible to do,” the official explained “So, we measure the number of mine-like contacts and the number which were actually mines, and we measure how many mines we may have missed.”

“Then, we try to analyse the reason why,” the official continued. “We try to determine why the contact has been misclassified, or why the contact was not found …. We try to learn from that.”

“One tricky part of mine warfare, in real operations, is you can have some intelligence of the threat, you can have an idea of how many mines have been dropped, but you will never know for sure,” the official explained. “What you will know is the number of mines you have found, but you will never know for sure how many mines are still remaining in the water.”

“It’s important information, because at the end we need to estimate the remaining risk for incoming traffic. So, we have some algorithms to try to determine what is the number of remaining mines and what the remaining risk could be,” the official added.

While the operators knew how many mines had been deployed for the exercise, this is not the same in real-world operations – even when working with close allies. For example, in the Black Sea, Ukraine revealed that it had laid defensive minefields in certain locations, but did not disclose mine numbers or mine types, as such information could assist Russian mine-countermeasures efforts.

Distance Learning

As regards the lessons learned in the combined ‘REPMUS’/‘Dynamic Messenger’ exercises relating to the role of ISR in MCM, the critical element was knowing that the AUV involved had the ‘legs’ to reach the operating area, remain on station as needed, and return to its host platform or port – but also knowing that the AUV could complete its mission effectively at distance given the reduced opportunity for operator engagement. In sum, there was a need to demonstrate that the vehicle could provide the required autonomy in delivery of the ISR and MCM taskings.

MCM serials have been conducted at ‘REPMUS’ for some time. Pictured is a REMUS 100 UUV being deployed for an MCM serial off Sesimbra for ‘REPMUS 2019’. In 2023, the exercise tackled an over-the-horizon MCM serial for the first time.
Credit: US Navy

“At the end, once on the spot in the corridor to be cleared, the AUVs will use the same sensors because the job remains the same,” said the NATO official.
The importance of the link between effective ISR and tactical-level MCM operations is underlined in the technology and operational roadmap NATO has set out for how it plans to continue transforming MCM capabilities and operations to keep pace with the changing nature of the threat.

In particular, here, there is a need to make UUVs increasingly smart in order to contribute to improved sensing, information sharing, and co-operative activity, Commander Stefan Pahl – a German naval officer posted at NATO’s Belgium-headquartered Naval Mine Warfare Centre of Excellence (NMW CoE) as subject matter expert for MCM doctrine, training, and standardisation, and for the use of robotics in operations – told a media briefing at Sesimbra.

Cdr Pahl – who was deployed to the exercise as a senior staff officer running the MCM serials – said that some of the main objectives of the roadmap include: developing UUV capacity to generate and support dispersed data management, including through designing standards for interfaces to enable such information sharing; and to provide alternative platform/capability options for conducting target identification, other than having to do so through visual means.

ISR also can also make a broader contribution here. Alongside the core requirement to find, identify, and clear potential mine threats, the other key product of MCM is “providing a reduction of risk for the follow-on traffic, [including] providing an estimate of what that risk is actually going to be”, said Cdr Pahl. “The risk is determined by the things we didn’t see: we’re not looking at what we found; we’re actually looking at what we might have missed.” Statistical analysis of what is or is not detected on the seabed, and thus the wider role of the surveillance component of ISR, are critical here.

Seabed Search

The role and importance of ISR was demonstrated against another key operational requirement put to the test during the exercises – the need to secure critical underwater infrastructure (CUI) on the seabed.

CUI security has become a central issue for NATO, following the occurrence of a range of incidents at sea since 2021. In November 2021 and January 2022 respectively, reports emerged of damage occurring to seabed cables at an environmental monitoring network off Lofoten, northern Norway and at a communications network off Norway’s Svalbard archipelago. Then, in September 2022 – amid the wider context of the Russo-Ukraine war – two Nordstream gas pipelines, which traverse the Baltic Sea floor, suffered explosions. The cause of each of the three incidents was assigned as unattributed acts of sabotage.

The relatively sudden, but perhaps not unexpected, emergence of what is now referred to as critical underwater infrastructure warfare (CUIW) is being met by NATO at all levels. At the strategic level, the alliance established the Critical Undersea Infrastructure Co-ordination Cell in Brussels, to provide a hub for countries, militaries, industry, and other stakeholders to engage and co-ordinate in addressing the risk. At the operational level, it is setting up the NATO Maritime Centre for the Security of Critical Undersea Infrastructure at MARCOM, Northwood, UK, to provide a hub for stakeholders to engage on operational tasks like enhancing MSA. Now, as demonstrated in REPMUS/Dynamic Messenger, NATO has now begun testing a range of tactical-level requirements, including technologies as well as tactics, techniques, and procedures, as part of an effort to develop and deploy a ‘fight tonight’ capability for deterring and defending against CUIW threats.

As a key objective in developing capability for CUI protection, serials were conducted in which UUVs were used to undertake ISR tasking in the vicinity of seabed communications cables, Commander Antonio Mourinha, a Portuguese Navy officer and Director of CEOM – the navy’s Maritime Experimentation Operations Centre – told the media briefing in Sesimbra. “We did a lot of experimentation in this area. It is definitely one of the areas where we need uncrewed systems, because this CUI is there, [and] we depend on this infrastructure.”

Uncrewed surface vessels participate in a critical underwater infrastructure (CUI) security demonstration at ‘REPMUS’/‘Dynamic Messenger’. The CUI serials were designed to test the role of uncrewed systems in locating, surveilling, and securing seabed cables.
Credit: NATO Maritime Command

“In order to protect the cables, we need to have the ability to surveil them and to detect any interference,” Cdr Mourinha added. As well as conducting surveillance to secure a cable, the serial also included the requirement to use surveillance to find the cable in the first place. This was a challenging task, given that the cable was only 18 mm in diameter, the NATO military official explained.

For CUI serials using MCM assets deployed to Sesimbra, “the aim was to figure out what the contribution of mine warfare assets to the protection of CUI could be,” the official said. Crewed mine-hunting assets carrying hull-mounted sonars and AUVs fitted with side-scan sonars were both deployed. The challenge here was searching for a cable that is far smaller than a mine, the official added. AUVs will bring particularly important capability, due to their ability to deploy to the seabed, to close the sensing range to the cable and reduce interference to, and improve definition in, the sonar picture.

The aim of the serials was to provide reconnaissance of the cable target, not only to locate the cable itself but to determine its track – the direction in which it is running – and then to assess its status and determine if any suspicious objects were in the vicinity.
As regards the nature of any suspicious objects, the official explained, “with mines, you know what the threat is. You have intelligence, you know the stockpile of the adversary – what kind of mines it would have. The threat against CUI could be an explosive charge, it could be a surveillance device, or something to connect to the cable to get information.”

“CUI is not mine warfare or [ASW]: it’s multidomain,” the official added. “It’s intelligence, it’s satellite surveillance, it’s MSA, it’s force protection, it’s a lot of things.” Mine warfare plays a key role in shallow waters, as MCM capabilities are designed to surveil the water column and seabed down to a certain depth. In deeper waters, UUV technology will come into its own in conducting CUI ISR.

Some of the testing at the exercises included experimenting with smart cables – cables with embedded sensors that provide in-built surveillance and data-gathering capacity. Such trials work reflected NATO’s wider focus in CUIW on building MSA and sharing such information.

Dr Lee Willett