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The UK government has highlighted the economic damage that would be caused if these global navigation satellite systems (GNSS) were disrupted. It estimates, for example, that a 24-hour GNSS outage could result in a £1.4bn loss to the UK economy, with a seven-day outage costing the economy £7.6bn.
While there is GPS (Global Positioning System), a US military technology, the EU has its Galileo system, Russia has Global Navigation Satellite System, China the BeiDou system and Japan has its Quasi-Zenith Satellite System.
Now the UK – post Brexit and without access to EU development of the EGNOS (European Geostationary Navigation Overlay Service) system – is increasingly becoming involved in this area, too.
Viasat demos UK EGNOS
For example, at the start of the year, Viasat demonstrated a UK satellite-based augmentation system (UK SBAS) for the first time. The aim is to deliver more precise, reliable navigation data from current GPS offerings.
A test flight, flown from Cranfield Airport using the National Flying Laboratory Centre’s Saab 340B aircraft, demonstrated the system in an aviation context.
This most recent UK trial aims to provide a first step towards a UK SBAS that can be used for critical safety of life (SoL) navigation services across air, land and sea. (UK applications can still use EGNOS but its SoL service was officially withdrawn in June 2021.)
Viasat explains that UK SBAS can offer positioning down to a few centimetres of accuracy, rather than the few metres provided by standard GPS. For aviation, the system gives pilots greater trust in their onboard instruments, for example, when pilots may not be able to physically see a runway or other obstacles due to bad weather.
“This means improved safety and fewer missed landings because pilots – especially smaller aircraft flying into regional airports and general aviation airfields – can get significantly closer to the ground during an approach before making the decision whether to land,” explains the company in a statement.
“Viasat’s research with one regional flight operator indicated that close to 40% of flights cancelled due to weather could have gone ahead had UK SBAS been available for its fleet. Around the UK, 19 airports had EGNOS procedures in place prior to leaving the EU. In total, as many as 72 airports no longer have access.”
With the aviation test complete, the trial will test the system in other transport applications, for example for rail, uncrewed aerial vehicles, or autonomous road vehicles.
Augmentation system
UK SBAS generates an overlay test signal to the US GPS that is fully compliant with International Civil Aviation Organization standards.
The signal is broadcast in co-ordination with the US Federal Aviation Administration (FAA), the European Space Agency (ESA) and the European Union Space Programme Agency. The broadcast capability for UK SBAS is provided by Viasat’s I-3 F5 satellite.
“This trial on a sovereign UK SBAS is all about delivering trust,” says Todd McDonnell, president, international government, Viasat.
“Trust for pilots in their tracking systems so they can stay safe in challenging conditions. Trust for the aviation industry more broadly so it can rely on data to operate more efficiently. And, in the future, trust that we can use highly accurate tracking to develop Britain’s transport system as new technologies come into play. We’re excited to continue the trial and see how far we can take it.”
Funding for the trial is coming from the Department for Transport via the ESA’s NAVISP programme.
It is being completed by a Viasat-led team of companies in the UK, including CGI UK, Cranfield University, the Cranfield National Flying Laboratory Centre, GMV, Goonhilly Earth Station, Ordnance Survey and Pildo Labs.
“This testbed project is vital in helping government understand the potential benefits of a UK SBAS,” says Dean Thomas, position, navigation and timing lead at the UK Space Agency.
“The flight trial both demonstrates the capability of UK industry in delivering space-based PNT solutions and illustrates the benefits of delivering UK PNT projects facilitated by ESA, through the highly flexible NAVISP programme.”
Southern hemisphere
Viasat highlights that a similar system, known as SouthPAN, is being developed for PNT services to be available in Australia and New Zealand.
Signals for this service would be provided by Viasat through one of its next-generation I-8 satellites, which are aimed to launch in 2027.
UK government policy
The UK government has outlined its policy for PNT resilience. A new framework to add PNT resilience – involving sectors such as emergency services and banking – has already been officially announced.
It involves the creation of a new National PNT Office, an updated PNT Crisis Plan to be activated if GNSS- providing PNT were lost, a proposal to develop the National Timing Centre, the development of a ‘Ministry of Defence Time’ system of last resort, and a number of other measures (see below).
“Enhancing our PNT resilience and long-term capabilities is key to both critical national infrastructure, our economic security and resilience and strategic high growth sectors like space, future telecoms, quantum and cyber security,” says Minister of State at the Department for Science, Innovation and Technology, George Freeman MP.
Ten-point plan
The government is working towards implementing (in its own words):
1 National PNT office: establish a National PNT Office in the Department of Science, Innovation and Technology – to improve resilience and drive growth with responsibility for PNT policy, co-ordination, and delivery
2 PNT crisis plan: retain and update a cross-government PNT crisis plan to be activated if GNSS-provided PNT is lost and identify and implement short-term mitigations
3 National Timing Centre: develop a proposal for a National Timing Centre – to provide resilient, terrestrial, sovereign, and high-quality timing for the UK (UTC(NPL)), including sovereign components and optical clocks
4 ‘MoD Time’: develop a proposal for ‘Ministry of Defence Time’ creating deeper resilience through a system of last resort, and use National Timing Centre-provided timing to support the Ministry of Defence
5 eLORAN (enhanced long-range navigation): to develop a proposal for a resilient, terrestrial, and sovereign eLORAN system to provide backup position and navigation
6 Infrastructure resilience: rollout resilient GNSS receiver chips, develop holdover clocks, and consider options for legislation on CNI sectors to require minimum resilient PNT
7 UK SBAS: develop a proposal for a UK Precise Point Positioning Satellite-Based Augmentation System to replace the UK’s use of the European Geostationary Navigation Overlay Service. Also, to monitor GNSS and to enable GNSS-dependent “high accuracy position” data, for autonomous and precision uses
8 PNT skills: to explore options for centres for doctoral training in timing and PNT and review PNT skills, education, and training for long-term sovereign PNT capability
9 Growth policy: to develop a PNT growth policy, including R&D programmes, standards and testing, to drive innovation for PNT-based productivity
10 Next-generation PNT: deploy existing R&D funding into a UK quantum navigator and investigate possible options for a UK sovereign regional satellite system.
NPL, the UK’s National Physical Laboratory and the technical authority for time and frequency, says it welcomes the UK government’s policy, to help tackle the risks associated with PNT.
It says that the NPL and government partners are “developing a resilient UK national time infrastructure through the building and linking of a new atomic clock network distributed geographically in secure locations”.
The aim is for this to form the source of resilient time for the UK. It will provide traceable signals into distribution systems such as a terrestrial eLORAN to provide backup PNT or even the ground segment of a UK space asset, strengthening existing infrastructure resilience. For long-term PNT resilience, says the NPL, it is crucial that we develop our own sovereign capabilities in this area, including a PNT infrastructure, its supply chain and a skills pipeline.
“NPL’s National Timing Centre research and development programme, developed in collaboration with innovators across the UK, is demonstrating the concept of a resilient timing infrastructure,” says Dr Pete Thompson, CEO of NPL. “Running until March 2025, the programme is the precursor to, and key building block of, developing a National Timing Centre, as outlined at point three of the Policy Framework.”
Royal Institute of Navigation
The NPL is not the only national body concerned with this area. The Royal Institute of Navigation (RIN) has positioned itself as the UK’s leading PNT body. Last year it announced that it is bidding to lead the UK’s focus for the development of positioning technology, including space-based developments and the possibilities of satellite constellations converging connectivity and timing/positioning services.
The RIN PNT advisory group was formed by the professional body in November 2022 and held its first public seminar on the subject of low earth orbit PNT. The group’s first event was supported both by Inmarsat and OneWeb with the aim to better understand the challenges of providing PNT services from large satellite constellations.
Rather than re-covering existing ground the intention is to address new challenges and applications, says the institution.
It writes: “The PNT Advisory Group has a goal to bring together individuals and organisations interested in position navigation and timing technology, policy, funding, collaboration, and research, taking input from all aspects of the PNT ‘world’ in areas such as policy and strategy development, technology development, economics, standards development and regulation, resilience, and security, plus liaising with equivalent groups around the world.
“It aims to provide a neutral place for the ‘PNT sector’ under the banner of a Learned Society and without bias or favour, to share knowledge and develop positions on key issues and opportunities, and to provide expert-led advice. Its scope covers all aspects of PNT from vision-based navigation to quantum sensing and space systems.”
