[time-nuts] Fundamental limits on performance

Magnus Danielson magnus at rubidium.dyndns.org
Sun Sep 13 12:02:06 UTC 2009

Mike S wrote:
> At 01:49 AM 9/13/2009, Hal Murray wrote...
>> > So, if I have a clock of some performance on Spacecraft A, is there a
>> > "simple" way to say how well I can do transfering that to Spacecraft
>> > B?
>> Do you want time or frequency?
> Time synchronization between spacecraft might take advantage of pulsars, 
> reducing the bandwidth used on inter-craft comm links. As frequency 
> sources, they are as good as Rb short term, and as good as Cs long term. 
> It should also be possible to use pulsars in a GPS-like way, for 
> position and speed.

I doubt it. Looks like another antenna and set of receiver electronics. 
Unless someone does something smart, it looks like it can be ruled out 
from power and weigth constraints. Pulsars are there thought and if 
several can be observed their beat frequency would be fairly low such 
that phase-relationships can act like a positioning in space and time. 
It may be good to have redundancy such that gravitational potential can 
be resolved separately.

Space-ship to space-ship or earth station needs to rely on the link 
between them. Synchronous carrier helps alot and stable clocks in each 
end require less dynamics for steering.


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