[LEAPSECS] drawing the battle lines

[Rob Seaman]

On Mar 20, 2013, at 2:29 PM, Warner Losh <imp at bsdimp.com> wrote:


> TAI isn't disseminated.


Well, yes it is.  From ITU-R TF.460-6:

E DTAI

The value of the difference TAI – UTC, as disseminated with time signals, shall be denoted DTAI. DTAI = TAI − UTC may be regarded as a correction to be added to UTC to obtain TAI.

The TAI − UTC values are published in the BIPM Circular T. The IERS should announce the value of DTAI in integer multiples of one second in the same announcement as the introduction of a leap-second (see § D.2).

TAI / DTAI could certainly be distributed better than implicitly through Bulletin C (http://data.iers.org/products/16/15458/orig/bulletinc-045.txt), but the two time scales address different needs.  Removing access to UT (~ GMT) does not in itself improve access to TAI.


> UT1 is a time realization of an angle. It is an irregular time scale because it is based on an imperfect oscillator whose frequency error and time error are not predictable. That's what makes it not a suitable times scale.


"The proposition seems beyond silly, for it implies that there were no time scales before the invention of the atomic clock."  - a wise person who eschews this arena.


>>>> 	10. the International Earth Rotation and Reference Systems Service (IERS) provides a means of accessing UT1 in real-time by means of routinely available predictions of UT1-UTC with precision 100 000 times better that the coarse approximation UT1 = UTC currently provided by means of coding UTC to match UT1 within 0.9 second;

>> 

>> This is irrelevant and is meant to imply that any issues with implementing a redefined UTC will be minor.  They will not be minor for my community.

> 

> If you take the product of inconvenience and probability of that inconvenience summed over all users, you'll find the change has a low expected impact.


Boeing didn't expect their batteries to go up in smoke either.  By all means the CCTF should explore the risk matrix, having taken it on themselves to recommend a change.

Rob

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