Lunar coordinated time

[ChristopherRabotin]

By the end of 2026, NASA should have a formal definition of LCT. Hifitime should provide some example reference to support that.

OSTP chief Arati Prabhakar's memo said that for a person on the moon, an Earth-based clock would appear to lose on average 58.7 microseconds per Earth-day and come with other periodic variations that would further drift moon time from Earth time.

https://www.reuters.com/science/white-house-directs-nasa-create-time-standard-moon-2024-04-02/

[mr5x5x5]

I had fun thinking about this all day today. Well, relatively all-day. Also A Relativistic Framework to Establish Coordinate Time on the Moon and Beyond by Neil Ashby, Bijunath Patla

[ChristopherRabotin]

Nice ! And I see you've implemented it in Python here. @philiplinden also worked with time dilation here.

If LCT is to work similarly to the TDB or ET time systems, then it'll need a reference epoch from which the drift happens continuously. If that reference is set to 01 Jan 2000 at noon, then we'd have accumulated 520 ms 62 μs difference with Earth time so far in these 8859 days.

Calculations for reference:

>>> from anise.time import *
>>> lct_delta = Unit.Microsecond*58.7
>>> num_days = (Epoch.system_now().timedelta(Epoch("2000-01-01 12:00:00 TDB"))).to_unit(Unit.Day)
>>> lct_delta * num_days
520 ms 33 μs 92 ns @ 0x253b19525c0
>>> num_days
8859.166822171665

[jmfriedt]

If it can be of interest, I have just uploaded Frederic Meynadier (BIPM) and Pascale Defraigne (Obs. Brussels) presentation at European Frequency and Time Forum (EFTF) this June 2024 on the topic at http://jmfriedt.free.fr/EFTF2024_moon.mp4 The video is of poor quality and the slides hardly readable but I can ask for a copy if interested.

[ChristopherRabotin]

Superb, thank you! I would be very interested in seeing the slides too if you can ask for a copy. Thanks.

[philiplinden]

If it can be of interest, I have just uploaded Frederic Meynadier (BIPM) and Pascale Defraigne (Obs. Brussels) presentation at European Frequency and Time Forum (EFTF) this June 2024 on the topic at http://jmfriedt.free.fr/EFTF2024_moon.mp4 The video is of poor quality and the slides hardly readable but I can ask for a copy if interested.

@jmfriedt Can you send me a copy of your slides? phil@moondao.com ❤️

[jmfriedt]

Should be now available at http://jmfriedt.free.fr/Meynadier_Defraigne_EFTF2024

[philiplinden]

fixed :) http://jmfriedt.free.fr/Meynadier_Defraigne_EFTF2024.pdf

thank you!!!!