NTP in in deep space

Our beloved NTP protocol appears to work in a deep space environment
(as tested in a simulation with a 4 hour RTT):

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Well I’m no expert at this, but I’m pretty sure the distance wouldn’t be fixed. If the device trying to synchronise time with Earth is travelling, then the response would take a little longer to arrive than the request does, and if we’re on another planet, then I believe they also move in relation to Earth which can change the distance.
Still interesting that NTP works this well with such a long latency, though would be interesting if they would take movement into account, how much that would affect the accuracy

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There are also relativistic effects that might need to be taken into account. IIRC ntpd was used on some space missions and it has some space-specific code, disabled by default.

I think most NTP clients would ignore measurements with delay larger than 16 seconds, following the RFC, and would need to be patched.

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Even for a direct point-to-point linkt, there would need to be some additional fields in the protocol where clients and servers can state their orbital parameters (if they are in an orbit), or their current vector through the solar system. Since the plan is to use relay satellites in orbits around different planets or moons (or the Sun), and to also relay packets using any other spacecraft that picks up a signal, and to dynamically route packets (using store-and-forward where needed), there would also need to be a way for each relay to add its own information, as well as the delay it added between receiving and forwarding a packet. Then times for the different legs of the round-trip could be pretty exactly calculated, allowing for way better accuracy.

An unmodified NTP running over unmodified UDP/IP won’t ever deliver the precision needed for e.g. planning and controlling the engine burn of a spacecraft. The protocols were just not designed to do this.

As far as I know deep space equipment are carrying their own atomic clocks on board. Independently of that, the aforementioned simulation is a nice experiment to find or even expand the limits of the NTP protocol.

On the apropos of talking about the limits of the NTP protocol. It is a bit off topic here, sorry. I propose the following experiment: having a system where the motherboard clock ticks twice the speed of the normal, and another one, where it ticks half speed. How nicely would the different NTP server implementations able to correct such a huge error? Server code, kernel code are permitted to patch before as preparation if there is a hard-coded maximum correctable error limit.

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How’s does the “NTP in deep space” experiment account for Einstein’s Time Dilation effect.

P.S. Meanwhile back on earth, we are still dealing with CrowdStrike.

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I think so. Even GPS/GNSS satellites have relativistic corrections to account for the altered time they experience being farther from Earth’s center of mass. This time-warping has been experimentally verified with two terrestrial atomic clocks synchronized then one taken atop a mountain for some time then returned and compared with the one that remained at low altitude.

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Don’t forget the Hafele-Keating experiment flying two atomic clocks around the earth :wink: link

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At last FOSDEM I saw a presentation of a Greek hackerspace who out of the blue received a phonecall inviting them to create a satelite. And so they did, despite a short deadline and many mandatory tests and other formalities.

The measure tape you see are… antennas! They return to their original shape when released in space, or when bumping other satelites.
Communicating over radio seems funny: when a single satelite orbits around earth… than most of the time you’re not directly facing it.

And what also becomes an issue is the doppler effect, especially if you (in this case) wish to do two-way communication.
And this one actually orbited even closer to earth than what GNSS satelites do; and slowly becomes victim of gravity, and is finally pulled into the strathosphere, fatal to their not-so-precise-predictable lifespan.

In case you wish to setup your very own GNSS, then libre.space is a non-profit foundation for open source hardware and software in space. Allowing space research to basically anyone. This satelite was part of the qubic program.

And another uncommon group of NOG’s: SatNOGS.

I do not believe it will work.

The reason is simply Albert’s laws.

Where time becomes different the further you go away from earth.

This has been demonstrated several times and also GPS’s sat’s need to be adjusted all the time, to compensate the difference.

In short, time is only relevant to the location you are, our case earth…but in space it’s irrelevant. As time can go slower compared to earth without you noticing it, yet the earth time passes faster when you return.

So what is the point keeping earth time in deep space?

One of the experiments was, you travel away from earth at the speed of light for a few minutes and then return.

Have fun…as it explains why time is useless in space compared to earth :grin:

I’m sorely tempted to correct some misunderstanding, but my overall feeling is I would just be feeding a troll, based on other threads in this forum…

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Hello @Bas , today is the 5th anniversary that you joined the NTP community. Many of us do not always agree with you (exclusively on scientific/technical topics), but that is part of the normal flow of life.
I consider you a valuable member of the community, please enjoy this cake: :birthday:.

What gives you the right to call names on people.
You do not know me.

I find this very insulting.

I just give my opinion on matters.

It may not agree with you. So be it.

Further is my goal to make this system better, for everybody.
Yet again, some may not agree.

But remember, I was the first to complain about fail of the monitor and proposed a new system.

Thankfully Ask did agree, and now we have a better system and good servers are not taken out of the pool anymore.

My goal is and always have been to improve the pool and give the correct time to people.

Thanks for the cake, I enjoyed it :ok_hand: