here’s how to deliver future-proofed time

It might not be apparent, but almost everything people do in this digitally connected world, from sending a text or e-mail to doing an Internet search or paying for something online, depends on accurate, resilient timing. Most electronic communications rely on digital infrastructure that is synchronized to a common time reference, enabling information to flow at a known rate. Accurate timing is also crucial for synchronizing and stabilizing infrastructure such as electricity grids, for helping to ensure the integrity of financial transactions, for steering machinery for precision agriculture, and for managing transport, logistics and postal delivery systems, among a host of other essential functions.

Today, the necessary timing signals come overwhelmingly from Global Navigation Satellite Systems (GNSS). These deliver signals from space, with only a radio receiver needed to receive and interpret them. Chief among them is the US-developed Global Positioning System (GPS). GPS is free to use, and the technology is mature: miniature GPS receivers are now embedded in every smartphone, at a cost of a few dollars per unit. This is an easy, low-cost way to reliably synchronize time, certainly compared with the old method of physically calibrating your clock to a reference clock at a national standards agency.

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But this success has bred complacency — and led to underappreciated risk. GNSS are far from fail-safe. In many parts of the world, organized-crime syndicates and military authorities are among those increasingly jamming GNSS signals (blocking them entirely) or spoofing them (transmitting false signals to provide misleading time and position coordinates). Disruptions to the signal due to extreme weather events are also on the rise. In some sectors, such as aviation, a multitude of systems would potentially be affected in the event of more-widespread outages. But there is low awareness of the risks — and protections are hugely variable between sectors.

The increasing vulnerability of time signals from space necessitates the development of alternative ways of accessing accurate, resilient and secure time. We (the authors) have been involved in varying capacities in technology and economic measures to deliver a nationwide, resilient terrestrial timing solution that is independent of GNSS in the United Kingdom. Here we set out three key steps that we think would help to facilitate the development of alternative time sources worldwide: increasing buy-in from business; linking up existing, heterogeneous local timing systems; and creating entirely new uses for time.

Getting buy-in from business

Constellations of GNSS satellites disseminate time from the national-standards laboratories that contribute to the formulation of the global time scale, Coordinated Universal Time (UTC). The GPS system was developed by the US Department of Defense during the cold war, initially for the exclusive use of the US military. Each GPS satellite carries multiple atomic clocks, which are ultimately synchronized with a representation of the UTC, known as UTC(USNO), generated by an ensemble of atomic clocks at the US Naval Observatory in Washington DC. The signals these satellites beam down to Earth enable users to determine the time to within an accuracy of 10^–7 seconds, or 100 billionths of a second.

Recognition in the 1980s of the wider potential societal benefits of GNSS led the United States to make an intentionally degraded, ‘selectively available’ version of the GPS signal accessible to everyone globally, free of charge. The full version was made public in 2000, since when its use has ballooned in a plethora of civilian applications. Other GNSS systems exist, such as GLONASS (operated by Russia), Galileo (the European Union) and BeiDou (China). But GPS remains dominant owing to widespread public confidence in a US-provided infrastructure and to the system’s earlier availability for general use, which means a large number of older receivers are only GPS-compliant. Some 5.6 billion end-user GNSS receiver units were in use in 2023, a number predicted to increase to almost 9 billion units in 2033 (see ‘Sky-high demand’). The economic benefits of using GNSS have been estimated to be around US$300 billion annually for the United States, $81 billion across Europe and from $9 billion to about $18 billion for the United Kingdom (see ‘Productivity plus’).

The potential costs of disruption to GNSS are similarly considerable: across all sectors, a report for the UK government in 2023 estimated these costs, per day, to be almost $1.9 billion for the United Kingdom alone. But whereas the economic benefits of using GNSS often accrue to individual firms, the economic cost of disturbances to the GPS signal — for example, the failure of the electricity grid due to a GPS outage that might affect transport, financial and communication systems — tends to be borne by all of society.

More onus needs to be put on firms and utilities that provide services through GNSS to invest in timing resilience. Regulation to increase the liability of individual firms, and personal accountability of senior managers for ensuring resilience of time, is one way to make this happen. There is also a need to support the development of alternative assured ‘holdover time’ capabilities: accurate, locally based clocks that can continue to provide time for a while if the main GNSS signals are lost.

The cumulative investment costs across every organization in every sector to provide such a holdover system are likely to be significant. Developing national public infrastructures for delivering resilient timekeeping directly from national representations of UTC — in effect, recreating timekeeping as a national public utility — is a way to reduce direct costs for businesses. Such a public utility could instil trust and confidence in users, and cover its costs by offering tiered, paid-for levels of assurance of time. In the United Kingdom, a supporting terrestrial clock system is being designed and developed as a nationwide time infrastructure through the National Timing Centre research and development programme (of which one of us, L.L., is head) at the National Physical Laboratory (NPL) at Teddington. This system is linked to UTC(NPL), the United Kingdom’s real-time realization of UTC.

But limited understanding of the need for alternative assured-time capabilities is a barrier to achieving business and political buy-in. A programme of public awareness about the use and importance of GNSS should be rolled out globally, emphasizing both the risks inherent in the current systems and the benefits of alternative timing systems for increased resilience and enhanced performance.

Linking up time systems

Crucial infrastructures, from financial services to transport and energy systems, are often interdependent. Yet they tend to operate as independent ecosystems, subject to their own legislation and with their own regulatory standards, policies, supply chains and digital ecosystems.

Little thought tends to be given to the security of timekeeping in the design and maintenance of the digital systems underpinning this infrastructure. Time’s intangible nature means that it often falls in the gap between cybersecurity and physical-security measures designed to protect digital and physical assets, respectively. When mitigating GNSS loss or disruption is considered at all, it tends to be by individual firms on an ad hoc basis. For example, telecommunications network providers often have atomic clocks distributed across their fibre exchanges to enable synchronization to be maintained for the Internet backbone even if GNSS signals are disrupted. Such mitigation measures are rarely tested robustly for the possibility of GNSS outages across all interconnected sectors.

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The increasingly interlinked nature of timing infrastructure implies that terrestrial clocks need to be integrated and able to coordinate time in the case of disruption to GNSS. This underlines the desirability of government intervention to provide a base capability that is accessible to all users wherever and whenever they need it. This might take the form of new legislation or regulation and standards to allow interoperability between essential infrastructures. It is part of the rationale behind the UK National Timing Centre’s research programme.

A further consideration is that the global supply chain for timing systems — from atomic clocks, time distribution and monitoring systems to user equipment — is currently sparse and lacks diversity. The ubiquity and utility of GNSS for time has resulted in industry investing in and developing receivers that are low in size, weight, power and cost, proliferating dependency on this single solution. (One of us, D.P., is head of the UK Hub for Quantum Enabled Position, Navigation and Timing, led by the University of Glasgow, UK, which runs a programme developing cheaper timing technologies.) A more diverse supply chain needs to be built to provide the enabling technologies to support a national timing infrastructure that can enhance the resilience of time. This needs to be complemented by an upgrade of the skills pipeline.

Private-sector investments in building such a resilient supply chain to provide reliable timing will depend on effective, long-term commitment from governments¹. Policy initiatives such as direct public investment, or incentives such as tax credits, interest deferrals and loans, must be immune to political winds of change to truly de-risk such investments. This could be achieved by regulating the minimum holdover time — the length of time any backup system can provide accurate timekeeping — across industries to ensure commitment to build and develop such time-based resilience. Such regulation needs to define the requirements for specific clocks with the accuracy needed to enable each national infrastructure to operate effectively.

Creating new uses for time

The extra revenue-generating opportunity of new timing systems is, on the face of it, limited when compared with the extra costs. A focus solely on managing risk and enhancing the resilience of time systems might not, therefore, be enough to convince firms of the need to invest in supporting the development of terrestrial holdover timing systems.