MODSOURCE

        [WEEDS\]MODSOURCE  MODFILE  ANTSIZE  [/BACKGROUND  TBG] [/OPACITY I]
    [/VERBOSE]

    Model the emission of a source at the  local  thermodynamic  equilibrium
    (LTE). The model paramaters (column density, kinetic temperature, source
    size, line width and velocity offset for each  species)  are  read  from
    MODFILE. The modeled antenna temperature is stored in the TB_MODEL memo-
    ry. For convenience the current spectra is also stored in a memory, OBS,
    so one can easily overplot the result of the model on the observed spec-
    tra.

    Arguments:
      MODFILE     the name of the file containing the parameters.  The  file
                  must  have  one line per species with at least six columns
                  containing respectively:

                  1) The species name
                  2) The column density for this species in cm-2
                  3) The exitation temperature in K
                  4) The source size in arcsecs
                  5) The offset velocity from the source VLSR, in km/s
                  6) The line FWHM in km/s

                  One additional column may be used to  select  a  different
                  origin for each species:

                  7)  The origin of this species (e.g. JPL or CDMS). If emp-
                  ty, species with any origin are selected.

                  The following options may be used at the end of the line:

                  /ABSORPTION  If this option is set, the component  is  as-
                  sumed  to  be  a foreground layer. See Belloche et al. A&A
                  559, A47 (2013) for details.

                  /PARTFUNC Q  Set the log10 of the  partition  function  at
                  the excitation temperature to Q. If not set, the partition
                  function values (log-log interpolated/extrapolated at  the
                  excitation  temperature)  from  the  selected database are
                  used.

                  Lines that start with a "!" are treated as comments.

      ANTSIZE     the antenna size in meters

    Options:
      /BACKGROUND set the background temperature to TBG, in  K.  Default  is
                  2.73.

      /OPACITY  I store  the  opacity  of the Ith component in the TAU_MODEL
                  memory. Components are numbered in the same  order  as  in
                  MODFILE, starting from 1.

      /VERBOSE    prints  partition function, lines frequencies, upper level
                  energies and degeneracies, Einstein coefficients and opac-
                  ity at the line center.