RE: Y2K [OFFTOPIC]

Richard B. Johnson (root@chaos.analogic.com)
Thu, 25 Jun 1998 12:56:29 -0400 (EDT)


On Thu, 25 Jun 1998 linker@nightshade.ml.org wrote:

> On Wed, 24 Jun 1998, Garst R. Reese wrote:
>
> > Just out of curiosity, how does MIR correct time for g and v? How many
> > beats/sec would a cesium clock register? Who's second?
> > --
> > Garst
>
> Hmm... Yes, I've always wondered what effect time dialation had on the
> atomic clocks on the GPS sats..
>

It's called Poynting-vector compensation. The GPS satellite orbits form
the outer surface of a sphere, with the center of the earth at its center.
If you could read the GPS time from the center of the earth, they would
all be identical. The actual wall-clock time of the satellites is not
important although it's maintained within a few microseconds of whatever
NIST says it should be. It's the difference between carrier
phase/frequency and time/position that makes GPS work. We don't care
who's clock is used.

Cheers,
Dick Johnson
***** FILE SYSTEM MODIFIED *****
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