On 11/28/21 2:11 AM, Andy Talbot wrote:
I would imagine there are already several caesium clocks on board the ISS,
anyway.
Don't forget there is a velocity component in relativistic time shift, as
well as gravitational, so using a moving platform like an aircraft or the
ISS complicated things a lot
Andy
www.g4jnt.com
I wouldn't actually think there's a Cs on ISS. What purpose would it
serve? We as time-nuts think "of course you'd have a precise source of
time", but really, there's not much need for timing on ISS on a scale
smaller than seconds, if that. NTP to timestamp files, for instance.
As a practical matter, there's not a lot of "infrastructure" on ISS,
i.e. there's no "house 10 MHz" - the experiments tend to be self
contained. When I was working on SCaNTestbed, which launched to ISS in
2012, there wasn't even an onboard real-time GNSS time/position feed. We
had a software GPS receiver as part of the testbed. What you would get
is a "playback" of ground predicts done by GSFC Flight Dynamics for
position and time over MIL-STD-1553 as part of Broadcast Ancillary
Data. And knowing precisely where you are on ISS is tricky anyway -
it's the size of a football stadium and flexes and moves on the scale of
meters. The BAD data was for some presumed "center of mass", as I recall.
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