Steve, thank you for this enlightening report.
In message: <[EMAIL PROTECTED]> Steve Allen <[EMAIL PROTECTED]> writes: : On Wed 2007-01-17T12:31:14 -0700, Warner Losh hath writ: : > It has been remarked that the current state of the art is that 100ms : > accuracy can be predicted about a year in advance only and that the : > models are constantly undergoing refinement. It has been estimated : > that IERS could issue leap seconds, with today's technology, about 3-5 : > years out and still be in a 95% or 99% band of certainty that the 0.9s : > margin is maintained. However, I can't find papers that show these : > models or point to any better data than hearsay... : : The best that I know of were the ones presented at the Colloquium that : the WP7A SRG held in Torino in May 2003. There was a time when the : host institution (IEN) was providing the proceedings online, but the : contents of that URL went away sometime around a year ago. (I wonder : if they may not have liked the conclusion that was reached.) : : In the spirit of promulgation I provide what they once did at : http://www.ucolick.org/~sla/leapsecs/torino/ITU.shtml : : The conclusion was originally a powerpoint drafted in real time, it is : http://www.ucolick.org/~sla/leapsecs/torino/closure.pdf : : The indications of how well predictions of UT1 might be done are found : in three presentations to which Felicitas Arias contributed. : There are two which were powerpoint : http://www.ucolick.org/~sla/leapsecs/torino/guinot.pdf : http://www.ucolick.org/~sla/leapsecs/torino/arias_2.pdf : and one which is a more verbose writeup of one of the powerpoints : http://www.ucolick.org/~sla/leapsecs/torino/arias_3.pdf I like figure 8, that shows that 20ms steps lead to 50ms steps lead to 100ms steps lead to 1s steps. :-) I also like the quotes: "Dating in UTC is ambiguous when a positive leap second occurs in systems other than those using hours, minutes and seconds; in this latter system the use of second "60" may a cause of difficulty." and "Thus UT1 is not, strictly speaking, a form of solar time" Also, did I miss figure 9 in arias_3? Proposal II has gotten much press here (the leap hour one), but Proposal I sounds a lot like what I've suggested: Use TAI time and let countries move the time zones when they feel like they no longer are close enough, but it kinda omits that last part... Warner