[tz] Sol 5000 for Opportunity
eggert at cs.ucla.edu
Sun Feb 18 02:46:11 UTC 2018
Tim Parenti wrote:
> Today, 16 February 2018, at 01:26:20.092 UTC, it is 01:01:06 Coordinated
> Mars Time on Mars Sol Date 51235
What's the source for these timestamps? It's an Earth reference frame, surely?
Because of relativistic effects, if an observer on Earth sees that Mars's 51235
01:01:06.000 CMT timestamp corresponds to Earth's 2018-02-16 01:26:20.092 UTC
timestamp, then I guess that an observer on Mars should see that the same CMT
timestamp corresponds to a slightly-different UTC timestamp, even assuming both
observers have error-free measurements, and that the difference will be
observable with millisecond-precision timestamps. This is due to both the
relative velocity of the Earth and Mars and to gravitational-field effects. For
millisecond/year precision Pan and Xie write that you need to figure in not only
the gravitational effects of the Earth, Mars, and the Sun, but also those of
Jupiter, Saturn, the Moon, and Venus (!). See their analytic model of
timekeeping for a Yinghuo-1-like mission in:
Pan J-Y, Xie Y. Relativistic algorithm for time transfer in Mars missions under
IAU resolutions: an analytic approach. RAA. 2015. 15(2):281-92.
The whole idea of time transfer between Mars and Earth brings into stark relief
what an easy job it is to track civil timekeeping on Earth, compared to how it
would be elsewhere. And Mars is an easy case. Someone should alert Elon Musk.
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