On 6/4/19 3:05 PM, Hal Murray wrote:
Are we developing these incredible devices just to push boundaries? Or do
they have some practical purpose?
I don't know of any current projects that need a significantly better clock,
but that's the sort of thing that wouldn't get a lot of publicity - just some
hand-waving discussions. "What if we could ..."
If you want some ideas to BS about...
You might ask the radio astronomers what they would do with a better clock.
navigation of spacecraft and making better gravity measurements of
planets and moons.
One of the "pushing the frontiers of clocks" things is that stuff that
starts in the lab eventually winds up portable. Sure, there's no cesium
fountain clocks in space (that I'm aware of), but we are doing trapped
mercury ion clocks (Deep Space Atomic Clock) and chip scale atomic
clocks (CSAC), both of which fundamentally enable new stuff.
Navigation of spacecraft today is done by precisely measuring the round
trip time of a signal to the spacecraft and back. This is great if you
want to know the position and velocity of the spacecraft *on the ground*.
However, what if the spacecraft needs to know where it is, by itself -
so it can autonomously navigate. For that, what you need is a good clock
on the ground, to transmit precisely timed signals (with appropriate
additional information), and the spacecraft receives them, with a very
good clock, and figures out where it is.
You might receive these signals at different times, so you need a nice
stable clock on board to be able to compare time signals received at
time T1 to signals received at time T2, some hours or days later.
One Way Nav is a *big deal* for enabling spacecraft autonomy,
particularly with multiple spacecraft constellations.
What would the radio guys do with better clocks? I'll bet you can dig deeper
into the noise when trying to find a spread spectrum signal.
It would be interesting to look at the history of similar advances. Cesium
clocks are now in widespread use. Rubidium clocks are a spinoff. Were any of
the common uses anticipated back when people were struggling to build the
initial atomic clocks? How much of the engineering associated with atomic
clocks was uncovered by the early researchers?
A lot...
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