[tz] Coordinated Universal Time (UTC) to retain “leap second”

Steve Allen sla at ucolick.org
Fri Nov 20 18:12:17 UTC 2015

On Fri 2015-11-20T12:55:49 -0500, Marshall Eubanks hath writ:
> No, that will not work. The UTC clock is providing not just the time, but
> also the rotation of the Earth (UT1). An atomic clock cannot do that (not
> at the km level), and the tables cannot provide leap seconds (much) in
> advance.

The almanacs are tabulated only a couple of years in advance, and over
that short an interval the current predictions of earth orientation
have errors about the same as the typical human error using a sextant.
Full precision already needs the DUT1 = UT1 - UTC, so if the radio
broadcast time signals and almanacs could arrange to agree on a new
time scale then a new difference value would preserve that ability.

Full disclosure, Marshall and I worked across the building from each
other using VLBI to measure earth orientation, so take this discussion
as an example of why the ITU-R could not forge a working compromise.

Steve Allen                 <sla at ucolick.org>               WGS-84 (GPS)
UCO/Lick Observatory--ISB   Natural Sciences II, Room 165   Lat  +36.99855
1156 High Street            Voice: +1 831 459 3046          Lng -122.06015
Santa Cruz, CA 95064        http://www.ucolick.org/~sla/    Hgt +250 m

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