Reducing DAS data with CLASS

To run the GILDAS software (class, greg, etc) first type (or enter this in your .login file):

setenv GAG_ROOT_DIR /jcmt_sw/CLASS/GILDAS
setenv GAG_EXEC_SYSTEM x86_64-redhat-g95
source $GAG_ROOT_DIR/etc/login

The latest installed version (October 2009a) can be reached at all 64-bit machines.

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

%class
class>file out jcmtdata mul
class>fits read jcmt_0131_001a.fits
(or alternatively)
class>fits read "/dir/subdir/jcmt_0131_001a.fits"
class>write n

%ls *.fits > files.cfits

jcmt_0131_001_a.fits

fits read jcmt_0131_001_a.fits
write
etc

class>@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