What happens to British ships when satellites don't work?

The Royal Navy and Britain's merchant fleet, along with most others around the world, rely on satellites for navigation - but what happens if they don't work?

It's a question that troubles the former First Sea Lord, Lord West of Spithead, who has spent months trying to find out if the UK has a back-up plan.

"My concern is that those people who are not friends with us are looking at ways to knock out satellite communications," he says.

"I thought I'd ask the government, I thought they'd have processes, but it became very clear from their answers that they don't understand what the problem is.

"There's no proper system for achieving communication if satellites collapse."

The Labour peer, who was the UK's first cyber-security minister under Prime Minister Gordon Brown, is convinced the government needs to act to protect the British fleet.

"If you don't have a fallback for a system, you can bet your bottom dollar that someone will exploit that," he says.

"The best fallback is probably old VHF [radio] systems. GPS can very easily be messed up. We know the Russians are practising this."

GPS - the Global Positioning System - was developed by the US military in the 1970s and has largely replaced pulsed radio transmissions as the main maritime navigation system.

"Everybody's lazy. They think satellites can do everything," says Clive Evans, a former Merchant Navy officer who represents seafarers' union Nautilus.

In the 1960s, ships had radio systems which used the same technology as today's mobile phones to pinpoint locations.

"Every country in the world has shut down these radio transmitters," Mr Evans, says, leaving seafarers "dumbfounded" because rogue states or an electromagnetic pulse from the sun could severely disrupt satellites.

"Solar flares can degrade radio signals emitted from Global Navigation Satellite Systems and even damage some of the electronics on board," says Jean-Charles Gordon, Maritime Analytics Manager of the maritime intelligence firm Lloyd's List Intelligence.

But, he adds, these would probably only affect a subset of the satellite constellation, with generally enough other satellites to provide global coverage. He says satellite constellations are being enhanced regularly with new satellites being launched to replace the older generations.

Purposeful disruption by hostile states or groups is another problem.

Mr Gordon says the Chinese Navy very frequently jams signals - overloading the receiver to the point that it can't hear the satellites that are around - in the South China Sea.

This allows it to keep operations secret and, because the equipment is so powerful, it can disrupt shipping "in a wide radius".

The could affect both Royal Navy and merchant shipping, he says, although it is understood that the Royal Navy uses systems designed to evade jamming.

Another disruption technique is spoofing. This involves providing false GPS data to a receiver, which then gets gradually more misleading, sending a ship further off-course, Mr Gordon says.

In 2019, the Stena Impero, a British-flagged ship, was probably lured by Iran into its waters using spoofed satellite data, says the editor of Lloyd's List, Richard Meade.

"You can think of commercial ships nowadays as vulnerable floating computer systems prone to hacking," says Mr Gordon, with radio spoofing and jamming being some of those cybersecurity threats.

Global supply chains are "quite fragile right now," says Mr Meade, but ships are not yet being hacked "on a regular basis", and he argues that hacks of company offices by cyber criminals currently pose a bigger threat to shipping.

"The skills of a seafarer 20 years ago were very different to today's," and there is a review under way by the industry to look at what is now needed, he adds.

Technology is advancing too quickly for regulation to keep up, Mr Meade says.

In 2015, the French and Norwegian governments decided to cease their eLoran transmissions, meaning navigation via radio alone has since become impossible in northern Europe.

eLoran remains the favoured radio back-up alternative for those concerned about the situation, such as Clive Evans and Lord West.

But without transmitters based in other countries, any radio-based system would only work in UK territorial waters. At this time, the government has no funded programme for an eLoran system in UK waters or British Extended Economic Zones.

In this year's integrated review of UK defence and foreign policy, the government said it was committed to strengthening the resilience of the "position, navigation and timing (PNT) services on which our critical national infrastructure and economy depend".

A Department for Business, Energy and Industrial Strategy spokesperson said: "The government is exploring ways to ensure PNT resilience for the UK, including a range of potential solutions in space and ​on land."

And, if all else fails, ship's officers are expected to know how to get by using "traditional methods", according to the UN International Maritime Organization.

Among them, a spokesperson says, is a "knowledge, understanding and proficiency in celestial navigation" - watching the stars.