NASA Is Now Tasked With Developing A Lunar Time Standard, Relativity Or Not

A little while ago, we talked about the concept of timezones and the Moon. It’s a complicated issue, because on Earth, time is all about the Sun and our local relationship with it. The Moon and the Sun have their own weird thing going on, so time there doesn’t really line up well with our terrestrial conception of it.

Nevertheless, as humanity gets serious about doing Moon things again, the issue needs to be solved. To that end, NASA has now officially been tasked with setting up Moon time – just a few short weeks after we last talked about it! (Does the President read Hackaday?) Only problem is, physics is going to make it a damn sight more complicated!

Relatively Speaking

You know it’s serious when the White House sends you a memo. “Tell NASA to invent lunar time, and get off their fannies!”

The problem is all down to general and special relativity. The Moon is in motion relative to Earth, and it also has a lower gravitational pull. We won’t get into the physics here, but it basically means that time literally moves at a different pace up there. Time on the Moon passes on average 58.7 microseconds faster over a 24 hour Earth day. It’s not constant, either—there is a certain degree of periodic variation involved.

It’s a tiny difference, but it’s cumulative over time. Plus, as it is, many space and navigational applications need the utmost in precise timing to function, so it’s not something NASA can ignore. Even if the agency just wanted to just use UTC and call it good, the relativity problem would prevent that from being a workable solution.

Without a reliable and stable timebase, space agencies like NASA would struggle to establish useful infrastructure on the Moon. Things like lunar satellite navigation wouldn’t work accurately without taking into account the time slip, for example. GPS is highly sensitive to relativistic time effects, and indeed relies upon them to function. Replicating it on the Moon is only possible if these factors are accounted for. Looking even further ahead, things like lunar commerce or secure communication would be difficult to manage reliably without stable timebases for equipment involved.

Banks of atomic clocks—like these at the US Naval Observatory—are used to establish high-quality time standards. Similar equipment may need to be placed on the Moon to establish Coordinated Lunar Time (LTC). Credit: public domain

Still, the order to find a solution has come down from the top. A memo from the Executive Office of the President charged NASA with its task to deliver a standard solution for lunar timing by December 31, 2026.  Coordinated Lunar Time (LTC) must be established and in a way that is traceable to Coordinated Universal Time (UTC). That will enable operators on Earth to synchronize operations with crews or unmanned systems on the Moon itself. LTC is required to be accurate enough for scientific and navigational purposes, and it must be resilient to any loss of contact with systems back on Earth.

It’s also desired that the future LTC standard will be extensible and scalable to space environments we may explore in future beyond the Earth-Moon system itself. In time, NASA may find it necessary to establish time standards for other celestial bodies, due to their own unique differences in relative velocity and gravitational field.

The deadline means there’s time for NASA to come up with a plan to tackle the problem. However, for a federal agency, less than two years is not exactly a lengthy time frame. It’s likely that whatever NASA comes up with will involve some kind of timekeeping equipment deployed on the Moon itself. This equipment would thus be subject to the time shift relative to Earth, making it easier to track differences in time between the lunar and terrestrial time-realities.

The US Naval Observatory doesn’t just keep careful track of time, it displays it on a big LED display for people in the area. NASA probably doesn’t need to establish a big time billboard on the Moon, but it’d be cool if they did. Credit: Votpuske, CC BY 4.0

Great minds are already working on the problem, like Kevin Coggins, NASA’s space communications and navigation chief. “Think of the atomic clocks at the U.S. Naval Observatory—they’re the heartbeat of the nation, synchronizing everything,” he said in an interview. “You’re going to want a heartbeat on the moon.”

For now, establishing CLT remains a project for the American space agency. It will work on the project in partnership with the Departments of Commerce, Defense, State and Transportation. One fears for the public servants required to coordinate meetings amongst all those departments.

Establishing new time standards isn’t cheap. It requires smart minds, plenty of research and development, and some serious equipment. Space-rated atomic clocks don’t come cheap, either. Regardless, the U.S. government hopes that NASA will lead the way for all spacefaring nations in this regard, setting a lunar time standard that can serve future operations well.


81 thoughts on “NASA Is Now Tasked With Developing A Lunar Time Standard, Relativity Or Not

      1. That’s good Soviet-era thinking. The old story was that they knew that the US spent a bunch of money figuring out the optimal number of launch tubes that should go in a ballistic missile submarine, so they just matched the number for their subs.

        1. Take a look at the Buran and compare it to the Shuttle. Jet intake features on the USAF F4 found on a MiG which were not necessary on that aircraft for their intended purpose on the F4. The Soviets copied exactly the former, absolute garbage US M17 cold war gas mask. Some other examples from military hardware in China.

    1. It’s a mythical time god from a place far away, but yet also all around us, and it will evaporate you into oblivion if you don’t put a daisy in it’s ass at least once in your lifetime.

  1. Don’t forget the ping latency on the moon is at best about 3 seconds for a full round trip

    Imagine the lag on multiplayer servers and shit.

    Yea ping of 3000ms not 3ms not 30ms not 300ms

    Irrelevant if using a radio or a laser to transmit

    Because light speed is a constant

    Unless it’s relative to a black hole or large mass then it changes based on perspective in relation to black hole or in relation to you outside black hole.

    To a black hole light doesn’t change speed, but to you u swear it does….

        1. Just to clarify what Paul means, it’s definitely not hours. Useful number to remember is that the distance from the Earth to the Sun is ~8 light-minutes. (at the 5% level, not exactly), and Mars isn’t that much farther from the Sun, so it can’t be hours.

    1. > Imagine the lag on multiplayer servers and shit.

      As a former modem user, I know all to well how this goes. :p Also there are satellite implementations today that are almost this slow, and are functionally this slow in bad weather (e.g. HTTP page load times).

      What I can tell anyone is that this enough delay to make anything “real time” all but impossible. They touched on this in The Expanse series where video conferencing had noticeable delays embedded in conversations (with the delay ms displayed on screen). The result is something that unfolds more like a “near time” say, wait, & listen conversational style. Doable, but nothing like a phone call.

  2. “Does the President read Hackaday?”

    “The Moon is in motion relative to Erath, and it also has a lower gravitational pull. ”

    I’m guessing not, unless the president can get a wifi signal on Erath.

  3. I’m puzzled how NASA or any other US institution can have the authority to define such a thing all alone. UTC on earth is an international affair. How comes that the Luna equivalent isn’t being coordinated/defined by a multi-nation committee or something along these lines? It’s 21th century, not cold-war era anymore. Humanity should solve such things together, right?

    1. This is a question of some organization stepping up to fill a perceived need. NASA is acting responsibly and generously to provide a definition that anyone can use. Or do you seriously believe that Burundi, Botswana, or Togo have something valuable to add here?

      1. Sure, but on the other hand, it’s about no less than defining a time standard for a whole celestial body. It certainly has a symbolic value, too.

        It’s like saying “hey, let’s define the standard language for all future colonies on planet Mars. We’re going for American English, obviously, but which dialect should it be? Northern, North Midland? Southern? (..) – Oh, it’s just a recommendation, of course! One that we will use, anyway. You’re free to join us or not. Just keep in mind that we’re not going to respond if you’re using anything else than what we use.”

        That’s about how it could look to others, I suppose.
        It’s a bit like with those docking bays on the ISS, I guess. There are at least three types?
        One USSR, one USA, one “universal” (adapter)?

        Why can’t people just agree on one common type?
        It would be helpful if two space capsules of different nations would need to dock in an emergency, for example.
        Standards are useless if everyone has his own, personal one.

        Here in Europe, we’re currently arguing about abandoning daylight-savings time and can’t decide whether summer time or winter time (ex normal time) should stay.

        I shudder to think if such a chaos will happen with Luna time, too.
        That’s why I think it might be wise if others are involved early on in the whole process.

        It might take longer, but it wouldn’t feel so much like a top-down decision than if NASA comes up with these things all alone (as usual).

        Inviting other space agencies into a discussion, formally, at least, would be a gesture of mutual appreciation.
        A standard Luna time would be something that concerns all of us, after all.

        1. Having actually RTFD, I see that international coordination is already baked into the policy: “This policy directs NASA to work with the Departments of Commerce, Defense, State, and Transportation to deliver a strategy for the implementation of LTC no later than December 31, 2026. NASA will also coordinate with other federal agencies as appropriate and international partners through existing international forums, including Artemis Accords partner nations.”

        2. Adding to what others have said: there’s no reason no other instance on earth can’t also define a lunar time standard. UTC, GMT, DST, (attempts at) decimal time standards, it’s not like we haven’t gone through a fair share of options here on earth either. As long as each time standard is clearly defined, it shouldn’t be too hard to calculate back and forth between them.
          Personally I’m much more worried about imperial and metric stuff than lunar time standard(s), as those are arguably much closer to arbitrary.

        3. You don’t ‘define’ a language that way. It’s defined by use.

          It’s why French used to be the language of diplomacy (and now it’s English) and how English became the ‘standard’ in maritime affairs.

          The place with the most dominance will use their language, because it’s easy for them, and others will choose to learn it because they can make more money that way.

          If LTC is useful, others will adopt it. If not, they’ll go their own way no matter how many countries were involved in it’s creation.

        4. It isn’t up to NASA to make others come to the table and support the effort. If NASA wants to do it, they probably will welcome any support from partner nations, but it’s silly to expect someone who wants to do it now to wait for others to want to do it too.

          In the end, if they don’t like it they have the option to design their own.

    2. Being one of the technically advanced people groups means these sort of things tend to get developed because your group of people needed them. Then if the rest of the world finds it convenient they probably adopt or at least use it unoffically too (GPS for example is pretty much globally used). Maybe they will change the names about a bit and have their local version that is directly mapped to yours, or spend months in committee meeting before the renamed version becomes a global standard…

      Though with how little most of the world trusts and likes the USA right now its quite possible this ‘standard’ will never get adopted globally no matter how good it is.

      1. “Though with how little most of the world trusts and likes the USA right now its quite possible this ‘standard’ will never get adopted globally no matter how good it is.”

        Um, well, this is certainly a point.
        I suppose the world certainly would like to like the USA, as it already did in the past.
        But it’s not easy the way that country currently acts/reacts.
        I mean, just compare the mentality of the USA of the 60-90s vs now.. Everything is so.. over the top?
        A bit more diplomacy, more co-operation and insight would be helpful, I suppose?

        The way it’s right now, the world seems a little bit uncertain about the USA, I suppose. It’s not hate or something, I think, but rather confusion (I know of no one who hates them).
        Especially considering their choose of recent representatives.
        I mean, the current message basically reads like: we don’t need anyone of you, we can do it all alone.

        Which feels a bit irritating, not to say rejecting.
        It may make other space agencies to evaluate future co-operation with Russia or China, eventually.

        That being said, I hope that reputation of the USA will become better again, eventually.
        The country once was a leading example in western culture, human rights and freedom.
        Would be welcome for this to happen again, rather than Idiocracy becoming a reality.

        These are just my two cents, of course, my current point-of-view. I can’t speak for others here.
        I’m also a foreigner, so I can’t really judge. My picture can be vague, at best, thus.

        However, it’s also obvious that this country is busy solving certain issues right now.
        The whole identity crisis thing, for example (gender, heritage etc).

        Or the broken job/dating market etc.
        It’s no wonder that this affects mental health of the population on the long run.

        I suppose that’s also a factor why so many things go “wrong” in that country.
        A few decades ago, people had more time to recover and reflect about things and had more time for friends and hobbies.

        1. I do appreciate you message and would say I mostly or maybe entirely agree with what you said. The problem I see is what do we do about it here. We do not even agree on basic fact anymore. I fear we are going to see our Nero moment soon. If we haven’t already

    3. One nation can propose a solution. If others don’t like it, then they’ll let us know how they don’t like it. Maybe they can propose something better. But someone needs to be first. It can be easier with a small team at first to come up with a first proposal. I’m sure it will eventually need to be run through some international standards panel be it’s accepted by everyone. And that doesn’t mean everyone will use it. Look at imperial vs metric.

    4. “One fears for the public servants required to coordinate meetings amongst all those departments.”

      Now add Russia, France, China, England, India, etc. to the table, and see if you can agree on where to have the first meeting in less than two years.

    5. The same way we did it before UTC – we just did it.

      No one has to use this time just as no one has to use UTC. It’s just really useful if everyone does.

      I mean, really, who had the authority to authorize the creation of UTC?

  4. Regarding the discussion about setting unilateral standards, good God, did anyone actually RTFD?

    “This policy directs NASA to work with the Departments of Commerce, Defense, State, and Transportation to deliver a strategy [eg. not a solution] for the implementation of LTC no later than December 31, 2026. NASA will also coordinate with other federal agencies as appropriate and international partners through existing international forums, including Artemis Accords partner nations.”

      1. But making a mess of it is not an option. Look what’s happened on planet earth – we’re still using the 12 month year FFS. IMO, It’s important to get it right and I for one will be using Moon Standard Time (or whatever they call it) to schedule my meetings from that point onwards.

        1. So what? Everything that matters is using something like posix time, and I’m sure the space missions will use something like that with some additional stuff to correct for the effects of relativity, just like GPS satellites do.

          And a 12 month year is perfectly fine, it fulfills historical context and is suited to life on Earth. You don’t just uproot that stuff and replace it with year zero abstractions just because you have engineer brain and you’re too blindered to see why people use traditional measures of time.

          We already have ways to keep time on existing spacecraft moving at relativistic speed which need an extreme degree of accuracy. The GPS sats I mentioned. Making up a moon time zone map is probably largely cosmetic

          1. Sure, nobody’s realistically going to change to a 13 month year on earth ….. and if moon time is as easy as you say it is (let’s just assume you’re correct) …. then what’s all the fuss about?

          2. >..what’s all the fuss about?
            Considering it comes straight from an executive order during an election year, I’m assuming it’s a public relations thing.

  5. It could be SO simple:

    Define some random point in time. Apollo 11 landing, start of first precision reference clock system on the Moon, first second of 1970 AD, 2000 AD, whatever. Call that point epoch. Count reference clock ticks (e.g. seconds, fractions of a second, whatever) from that point in time. Do not adjust the counter for any reason, just keep counting clock ticks. No time zones needed. Do that for every celestrical body with a solid surface that you visit. Do the same for every vessel that moves between celestrical bodies. Determinate the offset between clocks when you enter the orbit. Add / subtract offset to convert between clocks.

    That’s not even my idea, it is completely stolen from “A Deepness in the Sky” by Vernor Vinge.

  6. So at 58.7 microseconds / day we’d be over a second different if we start the moon clock using the unix epoch but work relative to lunar time, even before we get into deciding time zones for human use. Well, at least it’s less than the propagation delay. Sounds like sequencing events between locations may be the real issue?

      1. What are you saying could easily be compensated? Sure, we adjust for the fact that the rate of satellite clocks differs from Earth’s. But that compensation in the case of GPS sats is adjusting their rate to make them sync up and appear correct on Earth at the expense of being wrong in their local frame of reference. If you want a coarse timestamp to remain accurate for a long period of time, or if you want a precise timing signal, you need it to be calibrated to the local frame of reference for the Moon.

        What I’m talking about is more like this: events occur in the universe at various times which are often observable both from the Earth and the Moon. But depending where they occur, the Earth may be closer or the Moon may be closer, and they will move relative to each other and the event over the duration of the event. If all the differences were larger, or the speed of light was slower, you can imagine that the moon astronomers would observe that some supernova was a visibly different color, lasted a different duration, changed colors over the course of the duration, and began and ended at different times.

        So if you wanted to keep a record of many events over a period of time, then the relative positions of the event, the Earth, and the Moon throughout each event would need to be known, along with the relatively constant mass and shape of both bodies, just so you could say that one thing that was observed on Earth corresponded to another thing on the Moon and the sequence of sub-events was so-and-so at their origin. Now if some craft goes back and forth between the two, you have to include its flight path in the calculation for sequencing or throw up your hands and say your measurement of time is just going to stay flawed and you want a drink now.

        1. It’s by default calibrated for the local reference frame on the moon if it’s on the moon – because it’s embedded in the local reference frame.

          You only need to compensate to sync with clocks *outside* your reference frame.

  7. “Space-rated atomic clocks don’t come cheap..”

    Every GPS satellite has I think four of them ticking away onboard. And they already compensate for things like signal lag and relativistic effects of the height of their orbit, which would be a relatively (ha) simple variable to modify to make them work in lunar orbit. Are they also planning to make a lunar GPS (LPS?) system? I don’t know, but that would be a lot more complicated than simply having an accurate clock.
    I’m pretty sure that if we already have fleets of atomic clocks in GEO, we could spare a couple for Artemis.. Assuming the mission gets that far.

    I presume that since this comes from they executive office they don’t know about stuff like this, and simply want NASA to come up with a strategy proposal and maybe some pretty lunar time zone map that they can use in their publicity material.
    Which would be kind of cool, in a space travel agency sort of way. But I doubt it’s going to be anything revolutionary that hasn’t been proven since the 1970s.

  8. > the relativity problem would prevent that from being a workable solution.

    Then, uhm, how does literally every other piece of space hardware do it? Including, for example, every moon mission.

    GPS has relativity correction in it already – so you just use UTC, add a leap second every once in a while – and go. It’s not like you’re not going to be living underground once you get there or being controlled from earth until colonization.

  9. Since the Moon is leaving the Earth at about 3.8 cm (1.5″) per year I wonder how often the moon will get leap seconds added or *ponder* removed. And will local Moon second unit have the same duration as Earth second. It is good that NASA have a blank slate on the moon, to do things right like simple straight line lunar timezones that are at exact Longitudes (no wiggling around pre-existing countries).

    1. I am even imagining 100 lunar hour units in a lunar day (~27.32 Earth days or 655.72 Earth hours long). And maybe 100 Lunar minute units in a Lunar hour unit.

        1. I was thinking along the lines of people on earth with their 6x gravity and earth hours are only a sixth that of the hardworking lunar people!

          And you know that when someone on the moon takes an (lunar) hour long lunch, that they are eating one hell of a fine meal.

      1. Lookup “Selenographic coordinate system” the poles are obvious and the “Prime meridian” was selected to be on the side of the Moon that always faces Earth. Along a line from the centre of the Moon to the centre of the Earth.

    1. And what prefix would we use for earth, earths moon and mars?
      You do not want your Amazon galaxy oxygen delivery accidently going to the right post code but the weong planet.

        1. How about a four dimensional point in space time for the delivery to the nearest micrometer*.

          128 bit X
          128 bit Y
          128 bit Z
          128 bit time

          (ref: – “Quadruple precision (128 bits) floating-point numbers can store 113-bit fixed-point numbers or integers accurately without losing precision (thus 64-bit integers in particular). Quadruple precision floats can also represent any position in the observable universe with at least micrometer precision.”)

          But then there is the whole problem in agreeing on the zero point for the known universe. And if you miss your exact delivery time, not only has the destination changed location, the planet has rotated, the planet has moved in its orbit and the whole solar system has also moved. And working out where you should have delivered the item is then quite complex, just as complex as working out where everything should be for the delivery at the designated delivery time.

          1. Historically, the Earth was considered the center of universe for quite a long time until Copernicus came along and, wrongly, suggested it should be the sun. Designating Center of Universe (COV) as the center of the Earth would be a bit naff so we should probably pick some historical monument like a pyramid in S.America used for astrology or maybe somewhere else like Stone Henge, UK where astronomy was thought likely to be behind part of it’s construction design.

  10. “Does the President read Hackaday?”

    Well, he reads parenthetical directions like “Pause” aloud while reading his teleprompter, so you figure the odds.

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