Lux, Jim (337C) wrote:
On 9/13/09 5:02 AM, "Magnus Danielson" <mag...@rubidium.dyndns.org> wrote:
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.
The way we do this now is to lock the local reference oscillator (on the
spacecraft) to the uplink signal, which is derived from a Hydrogen Maser.
But that requires that the uplink be there, and there's really only about
half a dozen places in the world that can radiate the signal, and there are
multiple other consumers of the resource.
Which seems quite reasonable for your normal deep space probes, but for
a Mars Positional System (MPS) it needs to be fairly autonomous from
earth. However, you should consider that your normal approach may very
well be used for routine calibration of long-term drifts. You may
actually survive on rubidiums for long-term drift. The hold-over
effectively becomes a constellation (sats and surface nodes) averaging,
which could use the constellation control algorithms as already
developed for timing labs and TAI/UTC coordination.
Starting with a good quality clock helps (after all, no amount of fancy
control system can stiffen a wet noodle)
Certainly. But if they become too heavy artifacts to sling-shot to a
neighbouring planet...
Cheers,
Magnus
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