Subject: REVISED OFSP proposal - SOURCE ID KEYWORDS

From: [email-masked]
Date: Wed, 7 Jul 1993 16:09:53 -0400

Source ID keywords: An OGIP FITS Standards panel (OFSP) proposal (REVISED)

SUMMARY
The following proposal represents a revision of a previous proposal
which defined 3 keywords (CATID, CATREF and NCATREF) to be used to identify
sources in FITS headers.  As a result of comments from the HEAFITS group,
the OFSP has decided to amend the proposal.  We now propose a single
keyword, CATID, which can be used to represent the catalog designation +
the name of the source in the catalog.  CATID may be indexed (CATIDn) to
allow for alternate designations.  The full text of the proposal can be
found below.

PROBLEM
It is a common occurence that information in a FITS extension or file
refers to a single astronomical object.  In such cases it is necessary to
be able to provide the source identification in the file or extension
header.  

PROPOSAL
* The OFSP proposes that source id be coded using the following
header keyword:

KEYWORD         VALUE TYPE      COMMENT
CATIDn          string          name of source

where "name of source" is generally composed of 2 parts: a catalog
abbreviation  + the entry of the source in the catalog.  

* Users are encouraged to use catalog abbreviations as given in the
following articles (and future supplements)

        The First Dictionary of Nomenclature of Celestial Objects, Fernandez,
            Lortet, and Spite, 1983, A&AS, 52, No. 4.

        First Supplement to the Dictionary of Nomenclature..., Lortet and
            Spite, 1986, A&AS, 64, No. 2.

COMMENT cards should translate any abbreviation which are used for catalogs
not listed in these articles. Catalog abbreviations should be given with
spaces replaced by underscores; one or more spaces should separate the
catalog abbreviation from the source entry in the catalog.

* It is also proposed that ancilliary information such as the reference to
the catalog be embedded in COMMENT cards.  This alleviates the need
for definition of a new keyword and is sufficient since it is unlikely that
software would ever have to access this information.  

EXAMPLES OF USAGE
CATID   = 'HD 153919' / identification of source
COMMENT Henry Draper Catalog, Cannon, A., 1925 HCO

Multiple id's are allowed:

CATID1  = 'MPSLX 3' / identification of source
COMMENT MPSLX = ROSAT MERGED SOURCE LIST for pointing
CATID2  = 'HD 153919'  / identification of source
COMMENT Henry Draper Catalog, Cannon, A., 1925 HCO
CATID3  = '4U 1700-37' / identification of source
COMMENT 4th Uhuru catalog

CAVEATS
The CATID keyword, when indexed, should only be used to give alternative
identifications to the SAME source.  It is NOT to be used to give
identifications to multiple sources in a given observation.  

COMMENTS
Note that the CATID keyword is meant to augment, not replace, the standard
OBJECT keyword.  An obvious example is a ROSAT PSPC observation at the
North Ecliptic Pole in which a serendipitous source is discovered.  An
extension which contains the spectrum of the serendipitious source would
have the following keywords in its header:

OBJECT  = 'NORTH ECLIPTIC POLE'
CATID   = 'MPLSX 5' / source identification
COMMENT MPSLX = ROSAT MERGED SOURCE LIST for pointing

REQUEST FOR INPUT
Please send comments on this proposal to the HEAFITS mail exploder before
the next meeting of the OFSP scheduled for 21 Jul 1993.

Cheers,

Mike Corcoran

The OFSP:
Bill Pence, chair
Ian George, Secretary
Lorella Angelini
Mike Corcoran
Rich Fink
Tom McGlynn
Arnold Rots

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From: [email-masked] (Lee E. Brotzman)
Date: Fri, 9 Jul 1993 09:39:40 -0400

> abbreviation  + the entry of the source in the catalog.  

I was just wondering what the "Default index" of an indexed keyword is,
according to the NOST document (I'm at home and don't have my copy).
Barry Schlesinger --- I know you're out there -- care to comment about the
following usage of an indexed keyword?

> COMMENT Henry Draper Catalog, Cannon, A., 1925 HCO

I think that should be:

CATID1  = 'HD 153919'

Just to be unambiguous.  Other than that I think this proposed convention is
fine.  (Thanks for including the references to Lortet and Spite.)

-- 
-- Lee E. Brotzman                    Internet:  [email-masked]
-- Hughes STX                         DECNET:    NDADSA::BROTZMAN
-- NASA Goddard Space Flight Center   BITNET:    ZMLEB@GIBBS

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From: "BARRY M. SCHLESINGER" <[email-masked]>
Date: Fri, 9 Jul 1993 12:31:44 -0400

>From the OFSP

>> abbreviation  + the entry of the source in the catalog.  

Lee Brotzman muses

> following usage of an indexed keyword?

You rang?

> fine.  (Thanks for including the references to Lortet and Spite.)

The definition of "Indexed keyword" is "A keyword that is of the form 
of a fixed root with an appended integer count."  That language would
apply that the number should be there.  We have a model to go by. 
NAXIS is a distinct keyword from the NAXISn.  If we have one axis, we
call it NAXIS1.  Thus, if there is only one usage of the CATIDn 
keyword, it should be CATID1.

				Barry Schlesinger
				NOST FITS Support Office