[fitsbits] Future of UTC

[Clive Page]

In article <mailman.1049309941.10152.fitsbits at listmgr.cv.nrao.edu>,
Steve Allen  <sla at ucolick.org> wrote:
>At various intervals over the past three years we have seen indications
>that UTC might be re-defined by discontinuing all further leap seconds.

I have every sympathy with those who might be adversely affected by the
proposed change and note the possible costs of adapting to the lack of
leap seconds.  Astronomers who use space-based missions will probably
have a very different perspective, however.  I have been involved in using
data from space missions, mostly in X-ray astronomy, for over 25 years, and
know that the existence of leap seconds causes problems with the
development of software for every new mission. Many observatories in space
make observations of rapidly varying phenomena and take care to provide
timing accurate to milliseconds or finer.  These rely on quartz clocks in
the spacecraft, which have to be calibrated by reference to time standards
on the ground.  We try to educate all the software developers and users as
to the difference between TAI and UTC, and try to get TAI used exclusively
in the data analysis chain.

Unfortunately ground stations invariably use UTC, and have to insert leap
seconds manually.  The astronomer has little control over this
process, and over the years I have known several cases in which time
calibrations were badly messed up after the insertion of a leap second at
the ground station, with the result that, in the worst cases, several months
worth of data had to be reprocessed. Such mistakes also have their costs,
though it will be hard to put them in monetary terms.

In summary: my opinion is that many astronomers using space-based
observatories will welcome the abandonment of leap seconds.
 
-- 
Clive Page   cgp at le.ac.uk