UK’s SBAS signal repurposed for sovereign UK PNT capability

The tests will assess whether UKSBAS can develop into a full operational capability to support safety-critical applications

Artist’s impression of an Inmarsat-3 satellite. (Image: Inmarsat)

An Inmarsat-led team of companies in the United Kingdom has begun broadcasting a satellite navigation signal as part of a program to explore the creation of a sovereign national capability in resilient positioning, navigation and timing (PNT) for the aviation and maritime sectors.

The signal, being broadcast in coordination with the U.S. Federal Aviation Administration (FAA), the European Space Agency (ESA) and the European Union Space Programme Agency (EUSPA), is now stable and operational, enabling ongoing testing and validation by industry, regulators and users.

Inmarsat, a satellite communications company, alongside British partners Goonhilly Earth Station and GMV NSL, is delivering the UK Space Agency-funded tests with the European Space Agency via ESA’s Navigation Innovation and Support Program (NAVISP).

The UK Space-Based Augmentation System (UKSBAS) generates an overlay test signal to the U.S. GPS, compliant with International Civil Aviation Organization (ICAO) standards, to enable assessment of more precise, resilient and high-integrity navigation for maritime and aviation users in UK waters and airspace. It increases accuracy in positioning to a few centimeters of accuracy rather than the few meters provided by standard GPS.

This is a similar system to that already under evaluation in Australia and New Zealand, supported by Inmarsat.

Since leaving the European Union, the UK is not part of the Galileo satnav system and cannot use the European Geostationary Navigation Overlay Service (EGNOS) safety of life (SOL) services, which enable the use of GPS for airport approach and landing operations for aircraft. The UK ceased to have access to EGNOS on June 25, 2021.

By repurposing the SBAS transponder on Inmarsat’s I-3 F5 satellite in geostationary orbit at 54° west, the UKSBAS signal enables testing of this potential alternative system. Built by Inmarsat’s Athena partner Lockheed Martin and launched in 1998, I-3 F5 covers the UK as part of its Atlantic Ocean region service overlay. This makes it a suitable candidate to participate in this test and demonstrates the commitment to sustainability of Inmarsat with a satellite that has already served the equivalent of several low Earth orbit (LEO) satellite life cycles.

“The Inmarsat team is inspired by delivering solutions to new problems through technology and innovation,” said Todd McDonell, president, Global Government at Inmarsat. “Repurposing a transponder on a long-serving satellite to deliver a new capability to the UK, potentially a vital and enduring one, certainly lives up to that core Inmarsat ethos. Working with our fellow British companies at Goonhilly and GMVNSL to deliver such a capability for the country is very rewarding, and we look forward to reporting on the results.”

The tests will assess whether UKSBAS can develop into a full operational capability to support safety-critical applications such as airport approach and landing operations or navigating ships through narrow channels, especially at night and in poor weather conditions.

Goonhilly provides the signal uplink for the system from Cornwall; software from Nottingham-based GMVNSL generates the necessary navigational data.

“The UK’s thriving space sector is developing at pace, and British-led innovations like this have the potential to deliver crucial navigation services for our aviation and maritime sectors.” said Transport Minister Robert Courts. “That’s why this government is investing millions in new technologies to make our transport network even safer while boosting high-skilled job opportunities across the nation.”

UKSBAS is helping to regenerate UK strategic capabilities in this domain. The establishment of this new national platform creates the opportunity to evaluate high-integrity, resilient and precise navigation across the country, in its airspace and within surrounding waters. The project may be crucial for UK users who need accurate, high-integrity navigation capabilities to enable their operations, initially covering aviation and maritime operations but with potential extension into rail and road applications.

“Congratulations to Inmarsat, Goonhilly and GMVNSL on this impressive achievement,” said Paul Bate, CEO of the UK Space Agency. “In recent years, the UK Space Agency has invested in the development of UK expertise in positioning, navigation and timing (PNT), and the government’s commitment to strengthening PNT resilience is set out in both the National Space Strategy and Integrated Review, given its importance to our critical national infrastructure and economy. “This project is a great example of the innovation found throughout the UK space sector and demonstrates how we can work effectively with the European Space Agency to strengthen our national space capabilities.”