Re: [LEAPSECS] first use of the terms UT0, UT1, and UT2

[Steve Allen]

On Sun 2017-10-15T18:59:31+ Michael.Deckers via LEAPSECS hath writ:
>  Thank you for these interesting primary sources!

The more I reflect on this the more I realize that Nicolas Stoyko
attended and took notes on many of the astronomy/time/radio meetings
during the 1950s and 1960s.  Lots of the history of who said what when
is in the opening sections of issues of Bulletin Horaire, and detailed
in a way that is not typically found in the official proceedings.

The 1955 meetings are interesting because atomic time was a thing,
but atomic timescales were not yet a thing anyone had done, and
Ephemeris Time was a thing that a few people had done.
So in all those discussions it is clear that Universal Time is
unquestionably understood to be a measure of earth rotation.

Speaking of meetings, ITU-R WP7A meets in 10 days and looks likely to
discuss leap seconds.

--
Steve Allen  WGS-84 (GPS)
UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
1156 High Street   Voice: +1 831 459 3046 Lng -122.06015
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Re: [LEAPSECS] first use of the terms UT0, UT1, and UT2

[Michael.Deckers via LEAPSECS]

   On 2017-10-14 22:57, Steve Allen wrote:

Documents about the origin of the terms UT0, UT1 and UT2 have not been
widely available.  In the issues of Bulletin Horaire from the BIH in
1955 I have found a detailed synopsis of the IAU GA which decided
that the measurement of time should change in that fashion, and
also what I believe is the first published use of those terms.

http://www.ucolick.org/~sla/leapsecs/BH1955.html

These show the tensions between astronomers, physicists, and radio
engineers.  They provide insight into the level of understanding of
various participants and the goals they were seeking.  They also hint
at the incredulity of Nicolas Stoyko of the BIH as he got the answer
to his question "You want it when?", because the IAU resolutions from
1955 required changes by every observatory, every radio broadcast of
time signals, changes to all the computations at the BIH, and a whole
new level of rapid coordination between the International Latitude
Service and the BIH.


   Thank you for these interesting primary sources!

   They corroborate (or at least they are consistent with) the 
following

   secondary sources:

    ∙ Felicitas Arias and Barry Guinot who write:
  "The distinction UT0/UT1/UT2 was introduced in January 
1956. At the BIH,
   UT was an average of the UT0’s of the participating 
observatories."
   in "Coordinated Universal Time UTC: Historical Background 
And Perspectives".

   online at [syrte.obspm.fr/journees2004/PDF/Arias2.pdf]

    ∙ D H Sadler in "Mean Solar Time on the Meridian of Greenwich" in
  Quarterly Journal of the Royal Astronomical Society vol 19 p 
290..309. 1978,
  online at 
[http://articles.adsabs.harvard.edu/cgi-bin/article_queryform

 ?bibcode=1978QJRAS..19..290S] who writes:
    "As a result of informal discussions between BIH and the former
 (H Spencer Jones) and current (Wm Markowitz) Presidents of 
[IAU]
 Commission 31 [on Time], the following terminology was 
adopted and

 used from 1956 January 1:
 UT0 is Universal Time as formerly computed;
 UT1 is UT0 corrected for observed polar motion;
 UT2 is UT0 corrected for observed polar motion and for
 extrapolated seasonal variation in the speed of 
rotation

 of the Earth
 The adoption of this terminology was reported to 
Commission 31 at the

 1958 (Moscow) General Assembly [30: Trans IAU X, 489. 1960],
 but (although generally accepted) it appears never to have 
received
 formal approval by the IAU; it was not reported to 
Commission 4
 [Ephemerides], and was clearly intended for specialist use 
in the

 time services."

    ∙ the bio of William Markowitz in
  [http://ad.usno.navy.mil/wds/history/markowitz.html] who says
 "At the International Astronomical Union (IAU) meeting in 
Dublin in 1955 he
  proposed the system of UT0, UT1 and UT2 which went into 
effect within

  months and remains today."
   except that, nowadays, UT0 is useless because local sidereal 
time is
   a derived rather than an observed quantity, and UT2 is 
rarely used.


   Michael Deckers.

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