Re: [LEAPSECS] Leap seconds have a larger context than POSIX
On Sun 2020-02-02T17:59:20+ Michael Deckers hath writ: > The maximum deviation |UTC - UT1| <= 0.9 s as stipulated in > 1974 by CCIR Rec. 460-1 has never been violated until now. That violates the agreement that the difference between UTC and UT1 would be encoded as part of the time broadcasts. > > In one case it was broken specifically because a high official at CCIR > > conceded to a high official from USSR and directed the BIH to violate > > the wording of the existing agreement. > > Do you mean the only violation of applicable CCIR rules, the > introduction of a leap second into UTC at 1973-01-01? Right. Sadler covers this in his memoir and in several contemporary publications. Delving into this reveals more of the fear in the process. Several memoirs show that the principals involved with the creation of UTC with leaps were very concerned that the change of broadcast time signals might cause havoc with ships using celestial navigation. Reading through those shows palpable relief when they managed to evoke from the Maritime Safety Committee of the IMCO a statement that Rec. 460 would not cause difficulties with navigation predicated on the expectation that governments whose radio broadcasts used new UTC would issue notices about the change of their broadcasts. That meant that the Time Lords did not have their arses on the line if a ships might collide as a result of the new system. With the maximum difference of 0.7 s that could be encoded in the radio broadcasts not being able to handle the 0.9 s difference that put their arses back on the line. Other concern was expressed that exceeding the 0.7 limit might be blamed on the BIH and might trigger governmental review of the operation and funding of the BIH. At that time about 80% of the funds for BIH were coming from Observatoire de Paris as slush from their allotment from the French government. That was hardly an "international" arrangement, but BIH had only just been handed the responsibility for maintaining TAI specifically because any other arrangement would have required effectively duplicating the expertise and hardware of the BIH and finding a way to fund that. Prompting governments or journalists to open an investigation into the process of writing an international "technical" specification that was violated in less than two years was not a welcome notion. -- 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 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Leap seconds have a larger context than POSIX
On 2020-02-01 23:59, Steve Allen wrote: In every instance where a document specified a maximum deviation that agreement was later violated. The maximum deviation |UTC - UT1| <= 0.9 s as stipulated in 1974 by CCIR Rec. 460-1 has never been violated until now. In one case it was broken specifically because a high official at CCIR conceded to a high official from USSR and directed the BIH to violate fthe wording of the existing agreement. Do you mean the only violation of applicable CCIR rules, the introduction of a leap second into UTC at 1973-01-01? If so -- this was the choice of using either the date 1973-01-01 for the insertion of the leap second, or a later date before 1973-07-01. This is evident because at the time, the mean excess length of day LOD = d(TAI - UT1)/d(UT1) was observed to be >= 3 ms/d, which is more than 0.5 s per 6 months. Hence the choice was to either stick with the bound 0.7 s for |UT1 - UTC| as required by CCIR Report 517 of 1971, or else stick with the primary choices for the possible dates of the insertion of leap seconds. Apparently, the "high official from USSR" must have preferred the latter. Michael Deckers. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
