[LEAPSECS] Predicting the next leap second

[Demetrios Matsakis]

Here is  a plot that might interest some of you.  The blue curve  is  UT1-UTC, and you can see when the last leap second was inserted.  The goal is to be sure it never goes below -0.9, and the IERS obviously took no chances back then.   But remember that if they are making a decision 5 months in advance, the time of interest is 11 months later.   (The decision made last July was to forestall being too negative on the next June 30.)
But UT1-UTC is distorted by seasonal and lunar terms (the largest one being a 19 year cycle, with peak to peak about 0.3 seconds).  You can see a seasonal variation in the blue curve.  The red curve shows what happens if you take them out (the formulas are in the IERS Standards).   To predict what the IERS will decide about a possible June 30 leap second next year, I recommend you take your attention from the blue to the red, decide how to extrapolate the red curve to December 2021, and then map it back to the blue.   Then you can place your bet.  But will you win?  Don't ask me.

Demetrios, who is actually being paid to work on predicting this kind of thing.


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