SOLVE SPIDX

###
SOLVE SPIDX

            CLIC\SOLVE  SPIDX  [NOREFERENCE]  [BEST  n] [REAL] [/RESET] [/OUTPUT
        file]

        Calculate the spectral indexes of the sources in the  current  index  or
        the antenna efficiencies (Jansky to Kelvin) if the source spectral index
        is known.  The command can also be used to bootstrap source spectral in-
        dexes from a known source.

        It  should be used before computing any amplitude calibration, on an in-
        dex covering a reasonably short time interval to  avoid  possible  effi-
        ciency variations.

        The commands should be used in the following way:

            - The command SET SPIDX is used to define the spectral index of one,
            or several of the sources in the current index for which  the  spec-
            tral index is known. Frequencies and dates may be specified.

          -  Then the command SOLVE SPIDX will use the sources of known spectral
            index (optionally with matching frequencies and dates) to  determine
            the  efficiencies for all antennas. SOLVE SPIDX now gives the decor-
            relation factor relative to the  efficiencies  logged  in  the  scan
            headers (assumed to be the standard single-dish efficiencies).

          - SOLVE SPIDX then uses these antenna efficiences to compute the spec-
            tral indexes of all other  sources.  IF  the  keyword  "BEST  n"  is
            present,  the  n antennas giving the highest fluxes will be used for
            averaging (n is 1 to the number of available antennas).  Default  is
            n=3.

          -  The  command  SHOW SPIDX will give the current spectral index list.
            The reference sources are listed with a "FIXED" keyword,  while  the
            spectral indexes determined by SOLVE SPIDX are listed as "FREE".

          -  SOLVE  SPIDX  /RESET  can  be used to reset the spectral index list
            (i.e. remove from the list all sources whose spectral index  is  not
            fixed) before processing.

          -  SOLVE SPIDX /OUTPUT file [NEW] will produce an output file with the
            results printed for each antenna. Use keyword  NEW  to  open  a  new
            file.

          -  The  command  STORE SPIDX will store the spectral indexes and effi-
            ciencies in the headers of the observations in the current index.

        If no reference sources are available, the keyword NOREFERENCE should be
        given,  and  the  default efficiencies stored in the data header will be
        used (step 2 in the above list is bypassed).

        The keyword REAL forces SOLVE SPIDX to use the real part of the visibil-
        ities  instead  of  the amplitude to derive the antenna efficiencies and
        source spectral indexes. This is only for test purposes and must not  be
        used without asking an expert.