CAL

##
CAL

            MIRA\CAL [ALL|ifb] [/GAINS [/TCAL]] [/PHASE]
               [/OFF  [NONE]  [AVER]  [EQUAL]  [TIME] [TOTAL vMin vMax] /MASK d1
        [d2]]
               [/FEBECAL jfb]

        CAL calibrates the raw data of the observations loaded  with  MIRA\SCAN.
        By default, the first frontend-backend combination is calibrated, other-
        wise the frontend-backend combination number ifb, or all  frontend-back-
        end combinations if ALL is specified instead. If no option is specified,
        all three calibration stages are performed (i.e. normalization by  chan-
        nel  gains,  conversion from backend counts to a temperature scale, sub-
        traction of the off-signal with concatenation  of  autocorrelator  base-
        bands.

        CAL /GAINS normalizes the spectral band by the gainarray.

        CAL  /TCAL  Converts  from  backend  counts to temperature (forward beam
        brightness temperature if beam efficiciency set to  forward  efficiency,
        otherwise  main beam brightness temperature), using the TCal scale auto-
        matically determined when a "chopper wheel" calibration is loaded.

        CAL /PHASE Applies the phase calibration  for  XPOL  measurements  (i.e.
        VESPA  in polarimetry mode). The imaginary part of the cross correlation
        between orthogonally polarized receivers thus becomes the Stokes  V  pa-
        rameter (circular polarization). In order to have a valid phase calibra-
        tion, a calibGrid measurement with an identical spectral setup has to be
        previously calibrated.

        CAL /OFF subtracts the atmospheric emission as measured on the OFF posi-
        tion, and concatenates spectral basebands. For frequency-switched obser-
        vations, the subtraction of the reference signal has to be done in CLASS
        with command FOLD.

        For on-offs with continuum backends, a baseline  linearly  varying  with
        elapsed  time  is subtracted before further processing the data. The re-
        sulting fluxes and errors can be displayed with VIEW /PHASE.

        For on-the-fly data in total power mode, CAL /OFF has the following  op-
        tions:

        CAL  /OFF NONE does not subtract the reference signal, only concatenates
        spectral basebands. Both the reference spectra and on-source spectra are
        written to the CLASS file (see command MIRA\WRITE).

        CAL /OFF AVER uses as reference signal for off subtraction the unweight-
        ed mean of all available reference measurements. This is the default.

        CAL /OFF EQUAL uses as reference signal an unweighted mean of  the  off-
        measurements taken before respectively after the on-subscan.

        CAL  /OFF  TIME uses as reference signal a weighted mean of the off-mea-
        surements taken before respectively after the on-subscan. The first ref-
        erence has a weight decreasing with the time elapsed between the on-the-
        fly record and the first reference measurement (and the  weight  of  the
        second reference increases correspondingly).

        CAL  /OFF TOTAL vMin vMax uses as reference signal a weighted mean value
        of the off-measurements taken before respectively after the  on-subscan.
        The weighting is done in a way to ensure that the total power of the on-
        the-fly record equals the total power of the reference signal.  A  spec-
        tral  line  contributing  significantly to the total power can be masked
        with the arguments vMin and vMax.

        CAL /MASK d1 [d2 [d3 d4 ...]] uses the OTF subscans themselves as  atmo-
        spheric  reference,  masking  the source, which appears between dumps d1
        and d2 (and d3 and d4 etc). If only one argument d1 is  given,  this  is
        the  number  of dumps used as reference at the start and end of each OTF
        subscan.

        CAL ifb /FEBECAL jfb calibrates  the  frontend-backend  combination  ifb
        with the calibration measurement of frontend-backend combination jfb.