Time as a weapon – resilient PNT in the age of NAVWAR

Modern navies depend on fragile satellite signals for everything from navigation to weapon systems. As jamming and spoofing attacks surge in contested waters, Navies are racing to build layered defences against the growing threat of navigation warfare (NAVWAR).

“To master time is to master position – and with it, navigation,” said Maxime Gorlier, Head of Safran’s positioning, navigation, and timing (PNT) Business Unit. Rulers in the 16th, 17th- and 18th centuries understood this well. In their race to dominate distant lands and their resources, they dangled vast prizes for anyone who could solve the ‘longitude problem’. It was John Harrison, driven by the GBP 20,000 reward (worth millions today) promised under Britain’s Longitude Act of 1714, who delivered the breakthrough: a mechanical clock precise enough to let mariners fix their position by comparing the heavens to their time charts.

That legacy lives on in the atomic clocks orbiting Earth today. They are the atomic anchors of the satellite constellations that keep global time and guide naval fleets. The ‘T’ in PNT may sit at the end of the acronym, but it underpins everything: from navigation and communication, to weapon systems and drones; without timing, missions collapse. Yet these signals are fragile, and as great-power competition intensifies, time itself has once again become the contested terrain of NAVWAR.

Why timing rules the seas

As David Barrie notes in Sextant – A Voyage Guided by the Stars and the Men Who Mapped the World’s Oceans: “Celestial navigation would be easy if the sun and all the other heavenly bodies stood motionless in the sky.” From the 14th to the 19th century, astronomers and scientists wrestled with this problem: how could mariners use time to determine their position when far from land, navigating a restless cosmos of shifting earth rotations, lunar cycles, and planetary motions? Today, timing goes well beyond the need to navigate the skies to conquer the seas. Global navigation satellite systems (GNSS) – and their atomic clocks – are at the core of naval operations.

“If timing is corrupted or malfunctioning it could have a big knock-on effect to other systems,” Adam Price, Vice President PNT Simulation at Spirent Communications, told ESD. Timing is coordination: of onboard systems, of weapon systems, the fleet itself. If a ship’s clock drifts by just a few seconds, a missile may miss its target, or an ally may lose track of its position relative to the group.

That reliance will only deepen. As Michel Monnerat, Director of Bids & Advanced Projects in Navigation at Thales Alenia Space, explained, navies are increasingly turning to unmanned systems (UxVs) to scout, sense and strike. For them, precise PNT is indispensable, enabling autonomous navigation, communication and coordination. “There’s a natural, historical link between satellite navigation and the maritime domain,” Monnerat noted, adding, “That link is more important today than ever.” But anything this central quickly becomes a target, and in today’s strategic environment, PNT is no exception.

NAVWAR – turning time into a battlespace

Enter NAVWAR, now a key attack and defence vector, precisely because so much naval infrastructure relies on PNT. “Incapacitating an adversary by denying them the time reference, and therefore impairing key systems, means gaining combat advantage across the battlespace,” Price explained.

GNSS constellations (GPS, Galileo, GLONASS, BeiDou, etc.) orbit in medium Earth orbit (MEO), about 20,000 km up. By the time their signals reach sea level, they are already faint. At sea, they are further distorted by weather and ocean-surface reflections, and they are highly vulnerable to hostile action: jamming and spoofing.

 

Jamming involves overpowering a weak satellite signal with a stronger, localised signal, resulting in a total loss of the PNT signal, often indicated by a receiver displaying “No Fix” or “Acquiring Satellites”. “Jamming has become much more common in the past few years because the technology required is cheap and easily accessible,” Monnerat explained. In May 2025, for instance, the UK Maritime Trade Operations reported multiple GPS disruptions around the Red Sea, and the container ship MSC Antonia even ran aground after its GPS was jammed.

Spoofing, a more insidious and dangerous threat, involves transmitting false, deceptive GNSS-like signals to trick a receiver into providing an incorrect position, velocity, or time. Unlike jamming, spoofing provides a false sense of security, as the receiver may continue to function with seemingly valid, albeit erroneous, data. It is also more complex, requiring intimate knowledge of the signal one seeks to mimic.

“There can also be man-in-the-middle attacks,” Price warned, “where an attacker hacks the least-protected system relying on PNT and, from there, compromises the ship’s entire capability.” PNT is therefore a cyber vulnerability as much as it is a space and radio frequency (RF) vulnerability.

Decades of reliance on single-constellation GNSS have left navies with a strategic vulnerability, one that adversaries are now probing in earnest, under the banner of NAVWAR. Just as Harrison’s clock gave mariners redundancy against the chaos of the heavens, today’s navies are searching for new layers of assurance against the chaos of NAVWAR. These layers fall broadly into two categories: hardening the signal (protect and toughen) and diversifying it in orbit (augment).

Layer 1: Hardening the signal

While none of these threats are new, the resurgence of great-power competition and recent incidents in the Red Sea have made them far more frequent. For navies, the first line of defence is to toughen and protect their systems against jamming and spoofing – Layer 1.

Encryption is central, and both the US and Europe continue to develop new signals to harden GPS and Galileo against interference and spoofing. For the US, this builds on the M-Code, part of the ongoing GPS modernisation programme. Transmitted through a high-gain directional antenna, it boosts signal strength by around 20 dB and makes jamming far more difficult. A limited capability has existed since the Block IIR and IIF satellites launched between 2005 and 2016, 19 of which remain operational, while greater coverage comes with the Block III satellites, the first of which went up in 2018 – four are now active.

A September 2024 GAO report, however, noted that the Navy had intended to have a functioning M-Code receiver card installed on its Arleigh Burke test ship by that date, but no such testing appears to have taken place. As the GAO put it: “To mitigate some of these delays, the Navy and Air Force are planning an interim solution that would provide M-Code capability with some of their current receivers.”

 

There is no publicly available information on whether European Allied navies are making better progress in their integration of M-Code cards in their receivers. Germany has already received M-Code receivers, and industry players such as BAE Systems, Collins Aerospace and Safran can supply the technology. Yet given US delays, there is little pressure for Europe to rush integration.

Europe is instead betting on Galileo’s Public Regulated Service (PRS), an encrypted, interference-resistant signal reserved for government users such as navies, coast guard and police. “But there is one critical difference,” noted Michel Monnerat of Thales Alenia Space: “it has been designed to sustain several governmental usages and is also ready to operate in times of crises when access to other navigation services may be degraded – something that adds to its complexity.”

Galileo PRS has been live since 2016, and is about to become fully operational, but receivers are still being fielded. Under the Galileo for EU Defence (GEODE) programme, 30 companies from 14 European countries are developing standardised military PRS receivers, with demonstrations planned for 2026. In March 2025, Leonardo unveiled the first pan-European certified PRS receiver, but integration aboard naval platforms has not yet been confirmed.

Beyond strengthening the signal, navies can also protect it. Controlled Reception Pattern Antennas (CRPAs) add agility: multiple antenna elements adjust dynamically to block interference. They can ‘null’ the direction of a jammer or steer towards genuine satellites, especially when paired with sophisticated algorithms such as Safran’s Interference Detection Mitigation (IDM). The trade-offs are size, weight, power, and cost – but for naval platforms, the added resilience often outweighs the cost.

Yet protecting the signal is only half the battle. Navies are also working to diversify where those signals come from, adding redundancy in orbit.

Layer 2: Bring redundancy in orbit and autonomous navigation at sea

In addition to protecting and toughening, both Europe and the US are working to augment their GNSS constellations through the development of low Earth orbit (LEO) constellations – both GPS and Galileo being MEO constellations.

LEO constellations provide several benefits. At 500–1,200 km altitudes versus 20,000 km for MEO, their signals arrive hundreds of times stronger. They also move faster, circling the Earth in 90 minutes. That speed and power make them harder to jam or spoof and provide a back-up layer for navies reliant on GNSS.

LEO satellites are also quicker to develop and launch. As Xona Space Systems and Thales Alenia Space both note, the weakness of traditional space systems is the long cycle time: threats identified today may only be addressed by satellites launched a decade later, at huge cost. “What we want are small satellites complementing Galileo MEO that can be built quickly. If someone attacks, we can reinforce the space segment with enormous reactivity,” explained Monnerat. “With simpler technologies and a flexible production chain, we can put replacements into orbit much faster and strengthen the system when it’s needed.”

 

To that end, the European Space Agency (ESA) is leading the LEO-PNT in-orbit demonstrator mission. Approved by the ESA Council at ministerial level in 2022, the LEO-PNT in-orbit demonstrator mission involves two prime industrial partners – GMV (Spain) and Thales Alenia Space (France) – each developing a ‘Pathfinder A’ (one satellite plus a spare) and four ‘Pathfinder B’ satellites, bringing the total to 12. The full demonstrator is due in orbit by 2027. To meet this schedule, ESA signed a launch agreement with GMV, Thales Alenia Space and Rocket Lab: an Electron rocket will lift the first two satellites from New Zealand to 510 km in the sky in a three-month window beginning in mid-December 2025 – giving just two years from programme launch to the full demonstrator’s first orbit.

Across the Atlantic, the US is pursuing a different model: multiple commercial partners building redundancy into GPS from LEO. The U.S. Space Force is also running the Resilient GPS (R-GPS) programme, a constellation of smaller, more affordable satellites intended to resist interference and jamming. The first eight are scheduled to launch by 2028. Alongside, the US Air Force and Space Force are nurturing a broader ecosystem of commercial LEO-PNT ventures.

 

Private industry is already making headway. Xona Space Systems, for instance, is developing its own constellation and on 20 June 2025 launched Pulsar-0, its first production-class LEO satellite – just over a year from partnership signing to launch! In the coming months Pulsar-0 will demonstrate centimetre-level accuracy, signal authentication, jamming resistance, and even penetration into denied spaces like reinforced buildings or urban canyons. Crucially, it has been designed to deliver these capabilities via firmware updates to existing GPS-enabled devices. “Pulsar combines centimetre-level accuracy, high signal power, and robust protection into a single capability that’s usable by the billions of GPS-enabled devices people already have,” Luca Iuliani, Xona’s Director of Product, told ESD.

Yet LEO is not without challenges, as Adam Price explained, their speed introduces Doppler shifts (like the changing pitch of a passing siren), which complicates tracking and forces receivers to switch constantly. Their small form factor also means they lack the precise atomic clocks carried by MEO satellites. However, evidence is now showing credible steps forward to overcome many of these technical hurdles.

This is why navies favour layered approaches. LEO offers resilience, but it is not invulnerable. Non-satellite systems remain an important hedge, and alternate, autonomous solutions are key to augment overall PNT resilience. Safran, for example, has developed compact dual-core hemispherical resonator gyroscopes (HRGs) that double sensors on each navigation axis, boosting precision without adding bulk. Combined with atomic clocks and IDM algorithms, these systems allow platforms to switch autonomously and seamlessly to pure inertial navigation when GNSS signals are jammed or spoofed. For timing, this shield is just as vital: atomic clocks and oscillators ensure the mission keeps ticking, even when satellites fall silent.

The next frontier: Quantum, AI, and the future of naval PNT

Looking ahead, quantum technologies are set to bring significant advances to satellite PNT – from sensors that enable precise magnetometry mapping to quantum inertial sensors. However, as Gorlier noted, such technologies are unlikely to reach industrial maturity before 2040. In the meantime, the company is investing in hybrid approaches, combining mature inertial systems, vision-based navigation, and emerging quantum techniques – a reminder that resilience in PNT is never single-layered, but always built with redundancy in mind.

Companies like Xairos are pushing the frontier further. Their systems use entangled photons to transfer time with extreme precision and inherent security, synchronising clocks across ships, drones and networks to within a few picoseconds, even in contested RF environments. “What we’re doing at Xairos is leveraging quantum technologies to deliver very secure and very accurate time transfer – exactly what GPS was designed to do, but with far greater resilience,” David Mitlyng, CEO of Xairos, told ESD. For navies, the appeal is clear: trusted timing that cannot be jammed or spoofed. While the hardware remains bulky today, rapid progress in miniaturisation points toward compact, ruggedised systems and, ultimately, a global ‘time-as-a-service’ network with both military and civilian applications.

This vision is not just theoretical. In late 2024, Xairos took part in the KiQQer demonstration in The Netherlands, distributing entangled photons over a hybrid fibre and free-space link with picosecond-level synchronisation. Its work has also been endorsed by ESA’s NAVISP programme, which is backing future quantum time-transfer architectures. These milestones show quantum timing moving from the lab to the field, making the future feel a lot closer.

 

Artificial intelligence (AI) will also play a role, both in detecting jamming and spoofing attempts and in switching seamlessly between signals and sources. AI is not a panacea, but it could dramatically cut the time a ship might otherwise spend without GNSS coverage.

As Jerry Brotton writes in Four Points of the Compass: The Unexpected History of Direction: “[The blue dot indicating one’s position on digital maps] is now the most extreme expression of a long history of egocentric mapping… We just want to move as quickly and conveniently as we can, as the cardinal directions wither away.” For citizens, navigation has become about position alone, time forgotten. Navies, however, cannot afford that luxury. Harrison gave navies the clock. Today, with NAVWAR on the rise, time itself is a battlefield.

Alix Valenti