[ntp:questions] frequency adjusting only

David L. Mills mills at udel.edu
Thu Jul 10 03:37:41 UTC 2008


Ulrich,

That's what JPL tells me, but I don't think they intend the orbiters and 
rovers to cling to the nanosecond, even if the Proximity-1 protocol has 
some distinctly awesome timestamping capabilities. Best we could do in 
simulation with ephemeris data was 10 ms, but that was mainly due to 
Chebychev polinomial interpolation. More details in the Initerplanetary 
Internet project at www.eecis.udel.edu/~mills/status.html.

Dave

Ulrich Windl wrote:
> "David L. Mills" <mills at udel.edu> writes:
> 
> 
>>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
> 
> 
> Wow! Spacecraft steering with nanosecond accuracy! Or did they talk about
> longtime stability as in the past for long (sea) ship journeys?
> 
> Just wondering,
> Ulrich
> 
> 
>>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.




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