On Fri, 16 Apr 2004, Jamie Leech wrote:
> Here is a bit of heads-up with regard to the CONVERT package and what we
> at the JCMT foresee as our upcoming needs for ACSIS data.
The first two bits are purely AST modifications to the FITS channel. The
latter (SDFITS) is a bit more involved and can not just be AST changes.
> time. While currently AIPS++ remains our off-line reduction package of
> choice, uncertainty surrounding the AIPS++ project means that we want
> to be able to make FITS cubes that can be read into a variety of other
> packages (e.g. classic AIPS, CLASS), giving users more freedom.
SPECX reads CLASS format at the moment as well.
> (i) An ENCODING=FITS-AIPS++ option (for AIPS++). This may turn out to be
> identical to the ENCODE=FITS-AIPS, but I need to investigate this
> further. This is our priority item.
>
> (ii) an ENCODING=FITS-CLASS option, for CLASS import. Again, I need to
> investigate what sort of FITS class expects. Here is the spec for
> CLASS fits headers:
>
> http://www.iram.fr/IRAMFR/GS/class/node45.html
>
> Note the IMAGFREQ support for DSB instruments.
When we switch to NDF writing in ACSIS we will have to have two specframes
in dual sideband instruments. I don't think IMAGFREQ support will be
possible in the AST encoding unless SpecFrames themselves are extended to
support dual sideband frames (there would need to be two or three new
attributes, one to indicate which sideband is current (and which was the
primary sideband), the other to indicate the IF. Switching to the image
sideband essentially means adding or subtracting the IF and multiplying
CDELT by -1. Maybe there could be a DSBSpecFrame which inherits from
SpecFrame).
--
Tim Jenness
JAC software
http://www.jach.hawaii.edu/~timj
|