[LEAPSECS] long interval predicted

[Michael Deckers]

    On 2020-08-08 10:46, John Sauter via LEAPSECS wrote:


> UT2 captures the seasonal change in the length of day, so it can be
> ignored for long-term estimates.  The important number, therefore, is
> -0.00010, which I will call the UT1 slope.

     Perhaps "slope of UT2 - UTC (as predicted by the IERS)" would be a 
better
     name, as the formula of Bulletin A implies (by taking the derivative
     after adding the implied units):

                 d(UT2)/d(UTC) = 1 - 0.10 ms/d.

     But anyway, UT2 still contains known short period (<= 35 d) 
fluctuations,
     and currently, the combined amplitude of these fluctuations exceeds
     by far the indicated secular trend of UT2 during their periods.

     Another observation, namely the increase in the uncertainty of UT1 
- TAI
     as given in the long term EOP parameters (published by the IERS in
[https://datacenter.iers.org/data/latestVersion/38_EOP_C01.1900-NOW_V2013_0138.txt])
     from 4 µs to 30 µs since J2020.40 = 2020-05-26.6 may be a related 
effect.

     Michael Deckers.