SET STOKES

        CLIC\SET STOKES [HH|VV|HV|VH|NONE] [NATIVE|LEAKAGE|CORRECTED]
        [FREQUENCY|NOFREQUENCY] [EXACT|APPROXIMATE]

    Select the polarization product to be displayed and its correction mode.
    Several keywords can be supplied in the same command.

    SET  STOKES  LEAKAGE  removes source polarization to derive instrumental
    leakages. SET STOKES  CORRECTED  selects  instrumental-polarization  re-
    moval.  SET STOKES NATIVE disables both corrections, preserving the fre-
    quency and temporal-processing switches described below.

    SET STOKES FREQUENCY enables  a  frequency-dependent  source  model  for
    LEAKAGE  mode.  SET  STOKES NOFREQUENCY uses the stored reference Stokes
    parameters without frequency scaling. The default is  NOFREQUENCY.   En-
    abling  this  switch neither changes the stored coefficients nor enables
    LEAKAGE mode automatically.

    The reference values STOKES_I, STOKES_Q, and STOKES_U  refer  to  nu0  =
    R_FLO1  +  R_ISB*R_FIF1  (MHz). STOKES_SPIDX contains four model coeffi-
    cients: alpha(I), alpha(p), RM in  rad/m**2,  and  alpha(V).  Here  p  =
    sqrt(Q**2+U**2)/I is fractional linear polarization. The model is:

      I(nu) = I0 * (nu/nu0)**alpha(I)
      Q(nu) + i U(nu) = (Q0 + i U0) * (nu/nu0)**[alpha(I)+alpha(p)]
                       * exp(2i * RM * [lambda**2-lambda0**2])

    Wavelengths are in metres. Thus the stored Q and U are recovered at nu0,
    and the polarization angle changes  by  RM*(lambda**2-lambda0**2).   The
    fourth  coefficient  is  reserved; frequency scaling of V is not yet ap-
    plied. Use STORE POLMODEL to store the coefficients in selected scans.

    For temporal plots, SET STOKES  EXACT  applies  the  frequency-dependent
    correction and statistical-weight scaling to each channel before averag-
    ing. This is the default temporal mode. SET STOKES  APPROXIMATE  instead
    corrects  each averaged window/sideband at the mean sky frequency of its
    accepted channels. It avoids per-channel model evaluation,  but  may  be
    inaccurate  if the polarization changes rapidly across a window, for ex-
    ample through Faraday rotation. Continuum data  use  the  window  centre
    frequency in either mode.

    Spectral plots always apply the enabled model at individual channel fre-
    quencies, separately for each sideband, before sideband combination  and
    accumulation.  EXACT and APPROXIMATE affect temporal plots only and have
    no effect in NOFREQUENCY mode. Existing spectral-index flattening is ac-
    counted for in the model and statistical weights.

    For example:
      SET STOKES LEAKAGE FREQUENCY EXACT
      SET STOKES APPROXIMATE
      SET STOKES NOFREQUENCY

    SHOW STOKES reports the current correction, frequency, and temporal-mode
    settings. SET DEFAULT DISPLAY restores  NOFREQUENCY  and  EXACT.   These
    switches do not add spectral instrumental-polarization removal.