RE: OGIP/93-013 - A list of standard strings for HE missions,instruments & filters.

["BARRY M. SCHLESINGER" <BSCHLESINGER@NSSDCA.GSFC.NASA.GOV>]

I have gone through the proposed OGIP standard strings and have the 
following questions and comments.


The formsats given for the keyword=value statements appear to be
missing blanks.  A keyword of fewer than eight characters must be
filled with trailing blanks. There must be a space between the "=" and
the quote beginning the characters value.  Also, the recommended form
for character string values is that they be at least eight characters,
with trailing blanks, if necessary.  While this format is not required
for optional character values, it should be followed unless there is a
compelling reasong not to.  A sample keyword=value statement would be
as follows: 
DETNAM  = 'SDB     ' 
			
Because of portability issues, underscore is preferable to hyphen.  
Hyphens are standard for some FITS usages for historical reasons, but 
the recommendation now is to use underscore rather than hyphen if 
possible.

On page 6, there is a note that all strings in subsequent sections are 
to be considerered case sensitive.  What is meant by this statement?
Because some machines, such as the VAX, cannot recognize case, no
value required by the software to read the data should be case
sensitive.  However, both upper and lower case may be used in values
needed only for the scientific interpretation of the data by the human
reader, and, in fact, should be used where their availability on
systems that recognize case will make the meaning clearer, as in units
or the names of elements.  So perhaps what is intended here is that
case is significant in understanding the meaning of the values. 

Having two meanings for the values of IPC or SSS for INSTRUME for 
EINSTEIN can be confusing. The two non-recommended definitions should 
not be allowed, unless they are there to grandfather in existing files. 
If that is the reason, then the usages should be allowed but 
deprecated -- designated as permissible for existing data sets but not 
to be used in the future.

Since data sets have been produced for a number of the experiments
included, are the designated keyword values (names) for the different
missions, instruments, detectors, and filters consistent with current 
usage by the experimental groups?  In the same context, I note that 
indexing is inconsistent from usage to usage, sometimes starting at 0, 
sometimes at 1, sometimes at other values.  Does this indexing reflect 
that used in by the teams in referring to their instrument?  Normally, 
indexing should be consistent, beginning with 1, but the actual 
designations given by the experimenters would override such a 
principle.

				Barry Schlesinger
				NOST FITS Support Office