[LEAPSECS] BBC radio Crowd Science

Brooks Harris brooks at edlmax.com
Wed Feb 1 13:15:23 EST 2017

On 2017-02-01 12:46 PM, Steve Allen wrote:
> On Wed 2017-02-01T10:50:12 -0500, Brooks Harris hath writ:
>> https://www.itu.int/dms_pubrec/itu-r/rec/tf/R-REC-TF.460-6-200202-I!!MSW-E.doc
>> Section C Coordinated universal time (UTC) says "UTC is the
>> time-scale maintained by the BIPM, with assistance from the IERS..."
>> This says BIPM is the authority that maintains the UTC timescale,
>> doesn't it?
> Yes, but that is a "grandfathered" arrangement with a history.
> TF.460-6 is a rewrite from the original Rec.  460 which placed all
> authority with the BIH (International Time Bureau).
> In 1972 J. Terrien (the director of the BIPM who had been at the IAU
> meetings on radio broadcast time signals since 1964) noted that "the
> BIPM does no experimental work on the measurement of time and
> frequency" and apologized that "regrettable misunderstandings,
> especially between astronomers and physicists, have crept into
> discussions on time and frequency."
> That is to say that at the inception of leap seconds the BIPM
> had no component which could have defined a time scale.
> The advent of atomic chronometers made the role of the BIH unclear.
> The precision of satellite and interferometric measurements of the
> earth compounded this cloudiness.  BIH had oversight of axial rotation
> of earth, and two other agencies had oversight of the motion of the
> pole of earth.  That distinction made sense in 1920, but not by 1980.
> The overseeing astronomical and geophysical agencies decided to
> rearrange the divisions of responsibility beginning with 1988.  BIH
> and the two polar motion organizations were abolished.  The atomic
> chronometers went to BIPM.  All of the earth orientation went under
> the umbrella of IERS.  The CCIR got reorganized into the ITU-R in
> 1992, the recommendations were not revised for years after that.  None
> of the agencies who currently have responsibility existed when all
> this started, and the documents still do not quite describe how things
> actually work.
Right, thanks. It is a fascinating history, if somewhat frustrating when 
searching for a practical answer.

So, BIPM is the current authority of maintenance of TAI and UTC ("with 
assistance from the IERS"), is that right? And IERS makes their 
procedures for "assistance" known through the IERS Conventions?. And ITU 
and Rec 460 is the authority for "Standard-frequency and time-signal 
emission"? And Rec 460 points at BIPM Circular T.

As I read it there is, in fact, a chain of provenance through this even 
though its not so obvious. Of course, as I said, I think the facts are a 
scattered around and takes far to long to discover how it ties together, 
and I wish I had more confidence in my conclusions.

What's your opinion of the TAI-UTC value update topic? At or after the 
Leap Second?


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