[ntp:questions] frequency adjusting only
David L. Mills
mills at udel.edu
Wed May 14 19:33:54 UTC 2008
Evandro,
We didn't account for gravity and time dilation, as the errors in the
extrapolated ephemeris data dominated the error budget. I am told
accurate spacecraft navigation needs time to the nanosecond. In
principle, the Proximity-I protocol and NTP onwire protocol can do that,
I don't think the transceiver clocks and onboard rover clocks are
anywhere near that caliber.
Dave
Evandro Menezes wrote:
> On May 4, 2:37 pm, "David L. Mills" <mi... at udel.edu> wrote:
>
>>On symmetry, etc. There are both gravitational and velocity corrections
>>relative to both Earth and solar system barycentric time amounting to
>>some 15 ms, but current space missions don't worry much about that. The
>>mission times are relative to a clock onboard the spacecraft; nothing
>>else matters. Our Earth-Mars simulations didn't worry about these
>>effects either. I suspect disciplining an orbiter/rover clock to these
>>corrections will be dominated by the frequency noise of affordable
>>oscillators. Maybe not.
>
>
> Just curious, but did you have to deal with relativistic effects of
> relative time dilation as the craft speed increased?
>
> TIA
More information about the questions
mailing list