[LEAPSECS] the inception of leap seconds

[Steve Allen]

On Wed 2018-08-15T12:49:14+0100 Zefram hath writ:
> The announcement states a step size of 107600 us, but the expressions in
> tai-utc.dat imply a step size of exactly 107758 us.  The announcement is
> ambiguous as to whether this step size is specified in microseconds of UTC
> or of TAI, apparently ignoring the UTC frequency offset for this purpose,
> though the offset isn't anywhere near big enough to account for the
> discrepancy.  The 107758 us computed from tai-utc.dat is in microseconds
> of TAI, and the leap is only a few nanoseconds shorter in UTC.

I did not scan the pages, but there are two issues which gave detailed
tables of the values of the new time scale and the old time scale.
IIRC the second issue declared that the first issue should be
destroyed, but our librarian kept them both.  I also did not scan
many issues which gave the ex post facto corrections between the
actual times broadcast by USNO transmitters and the times that they
should have broadcast.

I think that having to re-do the entire set of comparison tables is
not surprising for the era when large amounts of manual effort were
being expended to keep track of UT2 (which was still the time that
CCIR and IAU had specified as the goal), the early form of coordinated
time by the BIH that everyone was supposed to try to broadcast, and
the atomic times.

In the US both USNO and NBS were publishing their own tables of
differences, as was the UK, and the BIH.  I suppose some other
harder-to-find agencies who had enough budget to do it might have
similar volumes languishing at places where the librarians were
conscientious enough to overrule the astronomers who knew nobody would
ever look at them.  But I tend not to scan those tables for my
reference because the real story is in the accompanying brief notes
about changes.

--
Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
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