Reducing DAS data with CLASS

When it seems (at the JCMT) that the GAG software (cfits, class, greg, graphic, gfits, astro) is not there,
you should type first:

setenv PATH /jac_sw/gag/linux-intel/bin:$PATH

If you prefer to use CLASS and other Gildas software to reduce your spectra these are the steps to take:
Unfortunately you have to use Specx to write the spectra to disk as fits files.

For single spectrum #131:

>> o-fil (open output file)
>> r-g-d 131
>> das-merge
(other commands if needed, e.g. fsw 8.3)
>> wr-sp 1 (to output file 1)

For raster/grid maps in scan #132:

>> o-fil (open output file)
>> r-g-r 132 (you will be asked for the output file and if you want to do das-merge, answer Y)

>> tofits (writes the data in a specified output file to disk as fits files).

Alternatively you can use g2f (gsd2fits). It writes a range of scan numbers to fits files doing a das-merge with default parameters (see the warning shown when typing the command). It usually works well for single channel spectra, and RxB dual channel spectra at the same frequency (samples and patterns).

For more complicated cases (frequency switching, 2 channels) some information is given here

The fits files will have these names:

jcmt_0131_001_a.fits
jcmt_0132_001_a.fits
jcmt_0132_002_a.fits
...
jcmt_0132_015_a.fits

These files can be converted into class format to file jcmtdata with Cfits (in the newest version use class):

%cfits
cfits>file out jcmtdata new (add new if the file does not yet exist)
cfits>read jcmt_0131_001a.fits
(or alternatively)
cfits>read "/dir/subdir/jcmt_0131_001a.fits"
cfits>las\write

%ls *.fits > files.cfits

jcmt_0131_001_a.fits

read jcmt_0131_001_a.fits
las\write
etc

cfits>@files.cfits

%class

For help within cfits, class, etc type help, or look at the GILDAS homepage.

In the newest version of Greg/Graphic the Explain command is not working. Here is a list of available tasks (run task).

Jan Wouterloot