[LEAPSECS] The Economist

Tom Van Baak tvb at LeapSecond.com
Fri Jan 13 10:00:00 EST 2012

> Just none of them have ever been on the table in ITU-R WP7A.)

> Rob

Yeah, given the wording, it will be amazing to me if the resolution passes.

But if it doesn't pass can you promise me one thing? Can you switch gears and use your energy be a focal point within
the astronomical community to actively promote the use of DUT1 as a floating point number?

That would solve two problems. One is that people (programmers, astronomers) could start using the high precision values
that are freely available through VLBI/IERS instead of the ancient 0.1 second fixed point version found in print or in
LF timecode broadcasts.

The second problem that would solve is astronomical code would start to explicitly use UT1 for precise angle instead of
making assumptions about how close or far UTC is from true angle. When someone uses UT1 they tie their desired angle
precision to the resolution of DUT1 that they fetch (i.e., the number of decimal places).

This tie is not possible with UTC since the angle precision is not explicit in any UTC time stamp. No matter how many
decimal places you see on a UTC time stamp there is no way to know what the angle precision is. Currently it is simply
*assumed* to be 0.9 seconds, but if that administrative threshold changes then code can break.

To me it seems better to avoid assumptions in code. Floating point DUT1 solves this. If over the years or decades
telescope source code would use DUT1 they way it was intended, then none of that code will break if UTC were to change a
little in the future.


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