FITS long integer support (was Re: [fitsbits] ADASS FITS BoF on Sunday)

[Steve Allen]

Recalling history, the 64-bit issue has come up before.

There was a significant discussion in 2001-09/10 which was led by
Bill Pence who produced the document seen here
http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/64bit/64bit.html

Bill took a poll and published these results on 2001-10-15:

   YES         20    69%
   NO           4    14%
   UNDECIDED    3    10%
   NO OPINION   2     7%
      Total    29   100%

Prior to that, the topic arose in 1998-07 as part of the editing of
the NOST standard for FITS.

The proposals already posted are not far from being couched in formal
terms, the characters on either side of the issue have not changed
much.

How do we determine at what point the balance should tip?

Perhaps if there were an "official FITS feature registry" we could
create a new keyword to be inserted into the PHDU of a FITS file.
Repeated instances of that registry keyword could be used to describe
the features of FITS which must be supported if the reader is to
understand the FITS file fully.

By default a FITS file would conform to Wells et al. (1981)
Other features could have names and meaning like
GROUPS                  Greisen et al. (1981)
XTENSION                Grosbol et al. (1988)
TABLE                   Harten et al. (1988)
IEEEFP                  IEEE floating point agreement (1990)
BINTABLE                Cotton et al. (1995)
WCS1                    Greisen & Calabretta (2002)
WCS2                    Calabretta & Greisen (2002)
INT64                   the current issue

And the registry should also contain significant unofficial things like

NOAOMOSAIC              Valdes (1997)
GROUPING                Jennings et al.
various Space Telescope conventions for FITS
lots of the content from
http://fits.gsfc.nasa.gov/fits_conventions.html
and anything else deemed relevant.

It would be relatively straightforward for a FITS reader to test its
capabilties against a set of such keywords and offer the option of
gracefully declining to interpret the full meaning of the file.

--
Steve Allen          UCO/Lick Observatory       Santa Cruz, CA 95064
sla at ucolick.org      Voice: +1 831 459 3046     http://www.ucolick.org/~sla
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