Open Lunar Timekeeping Project Blog Post Series: Blog 2

Contributor: Philip Linden

A cooperative, decentralized network of timekeeping devices could offer an agile, affordable approach to supporting an ecosystem of actors in cislunar space.

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Cooperative In-Situ Time References are Necessary for Coordinated Operations Beyond Earth Orbit

The Need for Local Lunar Time Utility

There are no Stratum-0 time sources in cislunar space. Today, all missions beyond Earth orbit receive time-transfer signals directly from Earth via ground stations.

There is currently little to no autonomous coordination between actors in cislunar space, so it's not yet necessary for peers to manage timekeeping autonomously. When multiple actors are operating on the Moon, it is usually led by operators on Earth.

But there are a plethora of missions to the Moon in the next decade, many of which involve autonomous actors and coordination between actors. For these missions to succeed, it will be necessary that a time synchronization protocol exists locally without requiring a direct connection between Earth and every actor.

Cooperation is Key

Every GNSS system in Earth orbit took a massive investment from mature space organizations. NASA has demonstrated that it may be feasible to operate a very precise atomic clock in deep space [Burt et al., 2021] to the tune of tens of millions of dollars each. But there's not enough time or investment to create a GNSS-like network of Stratum-0 time sources in cislunar orbit.

A cooperative, decentralized network of timekeeping devices (following the analogy explained in my first post) could offer a more agile and affordable approach to supporting an ecosystem of diverse actors in cislunar space. A cooperative network leads to incremental improvements while bootstrapping missions from the start:

● Access to a shared timekeeping source is more important than accuracy early on. Importantly, it doesn't matter if a shared reference is synced to any other actor, as long as all the participating actors are coordinated.

● Every actor that participates in the network contributes to the source.

● The entire cooperative network benefits when future missions participate.

• Early missions won't require very accurate timekeeping but would benefit from access to a time service.

• More precise clocks could be introduced with additional missions, supporting existing missions by participating in the timekeeping network. This reduces risk by incrementally improving the timekeeping network as it is necessary for future activities and doesn't lock the network into legacy technology.

• Later missions will likely require accurate timekeeping. If the existing accuracy isn't good enough, missions can bring their own clock. When a more precise clock participates in the cooperative network, the stability and accuracy of the entire network improve.

• Only a few missions need to actually have good timing, the rest just need to sync.              

In the next post in this series, I will explore the current state of play for timekeeping technologies in cislunar space and consider future architectures of an open lunar timekeeping utility.

Read the first blog post in the series, here.

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• Open Lunar Timekeeping Project Blog Post Series: Blog 1

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