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MIRA\CAL [ALL|ifb] [/GAINS [/TCAL]] [/PHASE]
[/OFF [NONE] [AVER] [EQUAL] [TIME] [TOTAL vMin vMax] /MASK d1
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-
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
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-
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
CAL ifb /FEBECAL jfb calibrates the frontend-backend combination ifb
with the calibration measurement of frontend-backend combination jfb.