Timesys note review

Markus Demleitner msdemlei at ari.uni-heidelberg.de
Tue Dec 4 09:52:31 CET 2018

Hi Steve, Hi Apps,

On Thu, Nov 29, 2018 at 10:30:51AM -0800, Steve Allen wrote:
> As Rob Seaman reiterates, very few observations have timestamps that
> merit the distinction between UT1 and UT.  UT1 implies that some
> special care has been taken in post-observation data reduction.  There
> are no tabulations with self-consistent re-reductions of the
> difference between UT1 and the available time signals from before the
> change from FK3 catalog to FK4 catalog on 1962-01-01.

I've changed the former UT1 in that table to:

  \item[UT] Earth rotation time. We do not distinguish between UT0, UT1,
  and UT2; applications requiring this level of precision need additional
  metadata.  This should also be used to label GMT times in datasets covering 
  dates before 1972-01-01.

(volute rev. 5251) and removed the former language on GMT in UTC.  Is
that minimally acceptable?

Also, I've put in François' and Mark's proposal of M?JD-origin both
into the text and the draft VOTable schema.  Putting it in convinced
me again that it's probably not a good deal in terms of standard
effort vs. possible benefit, but since nobody spoke out against it so
far, it's in now (rev. 5252).

A pre-built draft document is still at
http://docs.g-vo.org/timesys-draft.pdf, the draft schema is in volute

-- unless there's more feedback, this would be what I'd submit as
version 1.1 (except I'll update the frame/refpos enumerations in the

Thanks for the feedback, everyone,


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