MODSOURCE

        [WEEDS\]MODSOURCE  MODFILE  ANTSIZE  [/TCONT  TCONT]  [/OPACITY   I]
    [/KEEPCONT] [/VERBOSE]

    Model  the emission of a source assuming 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 brightness temperature is stored  in  the  TB_MODEL
    memory. For convenience the current spectrum is also stored in a memory,
    OBS, so one can easily overplot the result of the model on the  observed
    spectrum.  See the documentation manual for more details on the computa-
    tion.

    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 excitation temperature in K
                  4) The source size in arcsec
                  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.

                  /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:
      /TCONT      set  the  continuum level to TCONT, in K. The value can be
                  scalar (one value for the whole frequency range) or an ar-
                  ray name (same size as RY, one value per channel). Default
                  is 0.

      /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.

      /KEEPCONT   do not remove the continuum from the final spectra.

      /VERBOSE    print partition function, line  frequencies,  upper  level
                  energies and degeneracies, Einstein coefficients and opac-
                  ities at the line centers.