[time-nuts] Fundamental limits on performance

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Sun Sep 13 16:19:47 UTC 2009

On 9/13/09 4:43 AM, "Mike S" <mikes at flatsurface.com> 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.

This has been contemplated,

but it's a bit tricky to build a pulsar receiver that is, say, 1 kg, 1
liter, and draws 10-20 watts. (Chandra, which has provided a lot of the data
to support Xnav, is just a bit bigger than that..) And, you've already got a
radio comm link on board...

As the DARPA guy said:" At the 24th DARPA Systems and Technology Symposium
this summer, Steven H. Walker, the program manager for DARPA¹s Space
Activities Tactical Technology Office, said that XNAV may present some of
the agency¹s most difficult challenges."


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