[fitsbits] Questions about the 'REFERENC' keyword.

[Joe Hourcle]

I had some questions about the REFERENC keyword:

	http://archive.stsci.edu/fits/fits_standard/node40.html#SECTION00942320000000000000

	REFERENC Keyword

	The value field shall contain a character string citing a reference
	where the data associated with the header are published.


I could see a few different interpretations of this:

	1. It's similar to the 'FITS Serialization' in VOTable, where you
	   don't have the data attached, and can instead give a URL:

	   http://www.ivoa.net/Documents/VOTable/20121205/votable.html#ToC36

	   (although, in this case, I don't know if the URL would go to a
	   complete FITS file, or the data portion without the HDU)

	2. A URL to the archive or repository are available to
	   download from

	3. A reference (citation, URL, DOI or bibcode) to a published
	   research article that uses the data.

	4. A URL to a website with documentation on using the
	   data

So, question 1 : Which one is it intended to be used for?

The only real-world examples that I've managed to find so far is
WMAP LAMBDA, which seems to use it for a mix of 2, 3 & 4... but I don't
know that it's valid to define it multiple times:

	http://lambda.gsfc.nasa.gov/product/map/dr5/templates_fitshdr.cfm

And GOODS/FORS2, which gives a bibcode for the first results paper:

	http://archive.eso.org/cms/eso-data/eso-data-products/data-submission/spectrum-header.html


And question 2 is only partially related : 

As it doesn't seem to be used for use #1, is there some standard way of
providing a complete HDU with some reference to data that's not attached? 

I have some scientists who would like to review if the data's what they
want *before* they download really large files ... and I'd rather use
something FITS HDU-like, so they hopefully don't have to modify their
existing tools as much.


-----
Joe Hourcle
Programmer/Analyst
Solar Data Analysis Center
Goddard Space Flight Center