[ntp:questions] frequency adjusting only

Danny Mayer mayer at ntp.isc.org
Sun May 4 03:15:48 UTC 2008


Unruh wrote:
> mayer at ntp.isc.org (Danny Mayer) writes:
> 
>> Unruh wrote:
>>> "David L. Mills" <mills at udel.edu> writes:
>>>
>>>> Brian,
>>>> The longest delay NTP response was from the Moon, as simulated at JPL. 
>>>> Next step is the Mars orbiters and then the rovers. JPL discovered the 
>>>> max distance threshold had to be increased to handle the Moon delay.
>>> Thats only a few sec. 
>>> And it is symmetrical. Could probably still get usec resolution.
> 
>> Of course it's not symmetrical. You of all people should know better 
>> than that.
> 
> The speed of light differs in different directions?
> And if the response is fast, the distance has not changed much either
> (In a msec the moon moves about a meter, which is 3nsec, way below any
> computer resultion)and that is amost all perp to the earth.Ie, the
> difference in distance during the response time of the remote computer is
> negligible. If you aim for the moon when the moon is just setting and you
> are on the equator, the difference in path lengths is about 5usec, again, a
> completely negligible amount. 
> 
> Now of course the synchronization will not proper time on the moon, but the
> sync of the earth clock.

And neither the moon or other is moving along their geodesic?

Danny



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