A question on keywords for 3-D images

[bob at ipac.caltech.edu]

Hello,

The SIRTF project is designing the format of its output products.  One
of the products, for example, may contain 32-planes of 2-D data, all
with the same geometry.  This would normally be a straightforward
problem, just use a 3-D image, but there is a hitch ...

There is a set of at least 100 header keywords that have different
values for each of the 2-D planes.

There are a number of workable solutions to this and we could just
pick one and go with it.  However, a standard solution would be
preferable since it would be better understood and it could be used
directly in existing software.


Here are two of the options being considered:

 1) Append plane number to keywords

   Use a 3-D image and append the plane number to the keyword names,
   such as SIGMA01, SIGMA02, SIGMA03.  Is there any *STANDARD* way to
   do this (especially one that existing software uses) ?  Also, each
   plane may want to have its own BSCALE and BZERO. Is it possible to
   specify these values for the individual planes?


 2) Use FITS image extension

   Each extension would contain a 2D image and its own set of
   keywords.  Going to this form loses the 3-D nature of the data with
   each 2-D image looking like an independent image rather than being
   part of a 3-D cube.  Also, there is a concern is that many FITS
   readers and standard software may not be able to deal with files in
   this form.  It may not be supported well in IRAF, CFITSIO, etc. for
   3-D operations.

Thanks for any help,
 Bob Narron