[LEAPSECS] Cheating means more planning, not less

[Zefram]

Richard B. Langley wrote:

>How accurate

>are the predictions (especially the long-term ones) really?

>One would have to compare

>one of the historical empirical functions with actual UT1 data.


We discussed this in 2007-01 in a thread titled "UT1 confidence".
No firm answers were forthcoming regarding present IERS capability.

PHK noted that the accuracy estimation formula in Bulletin A gives
unbelievable results if applied to periods of decades.  We don't know
how far out that formula, or the DUT1 estimation formula, are intended
to be applied.

Steve Allen pointed at some interesting papers, of which the most relevant
was <http://www.ucolick.org/~sla/leapsecs/torino/arias_3.pdf>.  This paper
looks at (retrospectively) predicting UT1-TAI two and three years ahead,
and how well those predictions match reality.  These predictions were
made with a fairly naive algorithm, which in the short term performs
much more poorly than what IERS does.  The three year predictions were
all correct to within 1.0 s.

-zefram