What to do if OGIP conventions and the FITS standard are in conflict?

[maxnoe]

I just noticed a conflict between the OGIP conventions and the FITS standard, which is explicitly commented on in the FITS time paper, which definitions were taken over for the FITS standard version 4.0.

Specifically, in this instance, it is the keyword and its possible values specifying the time reference location.

In OGIP, it is TIMEREF with value 'LOCAL', which is given in GADF (but, pointing incorrectly to the FITS standard) and in the FITS time paper and the current standard it is TREFPOS with multiple possible values and 'TOPOCENTER' being the equivalent to 'LOCAL'.

While reworking the time definitions is also needed with respect to the current standard, I think we should take a decision on how to resolve conflicts between FITS standard and OGIP convention.

My personal preference would be to follow the FITS standard.

From the FITS time paper:

The OGIP convention uses the keyword TIMEREF and only allows values ‘LOCAL’ (i.e., Topocenter), ‘GEOCENTRIC’, ‘HELIOCENTRIC’, ‘SOLARSYSTEM’ (i.e., Barycenter); the convention contains also the somewhat peculiar keyword TASSIGN. We will not adopt these keywords in order to avoid confusion on allowed values and meaning. Instead, we adopt the keywords TREFPOS and TRPOS n

FITS Time paper: https://www.aanda.org/articles/aa/pdf/2015/02/aa24653-14.pdf FITS Standard Section 9.2.3 (TREFPOS): https://fits.gsfc.nasa.gov/standard40/fits_standard40aa-le.pdf OGIP definition: https://heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/rates/ogip_93_003/ogip_93_003.html