[LEAPSECS] presentations from AAS Future of Time sessions

[Steve Allen]

On Sun 2014-01-12T11:46:16 -0800, Brooks Harris hath writ:

> So it appears the reference to the International Astronomical Union (13th

> General Assembly, Prague, 1967) is where the recommendations from

> BIH come to the statement in

>

> l.A.2. Recommendations of the 5th Session

> of the Consultative Committee for the

> Definition of the Second

>

> RECOMMENDATION S 4 (1970)

>

> 4. The origin of International Atomic Time is

> defined in conformance with the recommendations

> of the International Astronomical Union (13th

> General Assembly, Prague, 1967) that is, this scale

> was in approximate agreement with 0 hours UT2

> January 1, 1958.

>

> So the 1958 origin was made *official* by this Recommendation. Is

> that your understanding?


I am not sure what "official" means in the context of recommendations
by one body which can be ignored by another body.

It is a statement by the CCDS produced under direction of the CIPM
which is an extreme shorthand for saying that they believed that the
atomic time scale being maintained by the BIH was based on that 1959
agreement that everyone would reset their atomic time scales to epoch
1958-01-01, and that the CCDS believed the BIH had done an adequate
job at that task, and the CCDS wanted the
next-step-farther-removed-from-the-technical-details delegates of the
CIPM to communicate the same thing up to the next-step-up... delegates
of the 14th CGPM so that they would officially approve the inception
and ongoing maintenance of TAI.

In this case the recommendation happens to agree with what IAU
comms 4 and 31 had said in resolutions 4 and 5 on page 182 at
http://adsabs.harvard.edu/abs/1968IAUTB..13..178S
so everybody was happy.

But in the same 1967 IAU GA were also resolutions 1 and 2 by
comms 4 and 31 (in that same document, but note that there
are typos in the enumeration and pagination) which were considered
important enough that the entire GA approved them as resolutions
5 and 6 seen on page 41 at
http://adsabs.harvard.edu/abs/1968IAUTB..13...41.
and the CGPM utterly ignored resolution 5b, so not everyone
was happy.

I find that the last point at which everyone was in agreement about
what the meaning of things were was the 1964 IAU GA discussion in
http://adsabs.harvard.edu/abs/1966IAUTB..12..304M
which was written by none less than astronomer W.  Markowitz,
radio-timekeeper H.M.  Smith, and physicist L.  Essen which was
included in the resolutions (see page 16)
http://www.iau.org/static/resolutions/IAU1964_French.pdf

By the time of the 1967 IAU meeting the statements by various folks
who reported the situation in the CCIR and the BIPM seemed to be using
imprecise paraphrases of what had been recorded in the proceedings of
those other agencies.  The documents from the different agencies use
different terminology when describing what they must have meant to be
the same thing.  That left room for paper consensus without actual
agreement on the mechanisms.

Up until 1970 all of the CCIR recommendations about radio broadcast
time scales were basically descriptions of the existing best
practices.  Recommendation 460 became prescriptive of a change which
had not been implemented by anyone, and its prescription contained no
instructions about the details of accomplishing the change.  The CCIR
working party rushed to come up with in interim implementation
document before the 1972 deadline.  During the next decade the CCIR
rejoiced as they saw 460 get adopted by the IAU, the CGPM, the WARC,
the CCITT, the governments of France and Germany.  Nobody seems to
have stopped to ask just how exactly those leap seconds were supposed
to be communicated nor handled by systems that could not interpret
a telegram from the BIH.

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