Re: [art] summary of updates - draft-time-touch

[Steve Allen <[e-mail]>]

On Mon 2017-04-17T14:32:57 -0700, Joe Touch hath writ:
> A new version of I-D, draft-touch-time-02.txt
> has been successfully submitted by Joe Touch and posted to the
> IETF repository.

UT0 is not "rarely used", but UT0 belongs in this document for the
sake of history.  UT0 was the only form of date/time which was
available from any source up to around 1950.  Thus UT0 was the basis
of official/legal times until then.  Various radio broadcast sources
of time differed from others by 0.1 second or more until after 1960.
UT0 had become unavailable from any source before the late 1980s.
A reference document for UT0 (and the other forms of UT) is Sadler (1978):
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1978QJRAS..19..290S

UT2 is not "rarely used", but UT2 belongs in this document for the
sake of history.  UT2 became available starting around 1956.  In 1959
UT2 became the recommended goal for radio broadcast time signals, and
thus UT2 underlay the basis of official/legal times for just over a
decade.  No technical body was fully comfortable with the concept of
UT2, and the folks doing radio broadcast time signals did not claim to
be providing UT2.  No sources were providing UT2 nor anything based on
UT2 starting with the inception of leap seconds in 1972.
Reference documents for the use of UT2 are CCIR Recommendation 319
(1959) and CCIR Recommendation 374 (1963,1966).

UT1R does not belong in this document.  UT1R is never used as a time
scale.  It serves little purpose other than to guide the eye toward
seeing the rapid changes in earth rotation that result from large
atmospheric storm systems and the slower trends of UT1 resulting from
oceanic and core/mantle interactions.

UT1 is more than "widely used as the basis of calendar days".
UT1 is the conventional measure of mean solar time descended from GMT.
Twenty six nations agreed to use mean solar time as the basis of the
Universal Day (the calendar day for diplomacy, commerce, etc.)  in the
text of Resolution 5 at the International Meridian Conference in 1884,
and GMT remains the legal basis of time in many countries.

Ephemeris Time does not precede Universal Time.  ET did not exist
until the 1950s.  UT had existed since the 1884 International Meridian
Conference, and the name Universal Time was agreed at IAU in 1928.
https://www.iau.org/static/resolutions/IAU1928_French.pdf
The reference for "Newcomb's tables" in the section on ET is
"Tables of the Four Inner Planets" 2nd edition (1898)
https://ia801005.us.archive.org/11/items/06AstronomicalPapersPreparedForTheUse/06-Astronomical_Papers_Prepared_for_the_Use_text.pdf

The list of major satellite navigation system times woefully ignores India:
https://en.wikipedia.org/wiki/Indian_Regional_Navigation_Satellite_System

--
Steve Allen                    <[e-mail]>              WGS-84 (GPS)
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