Determining the passband curves

The first operation is to select in the current index the calibrator observations performed during the time period when calibration is needed, and to plot the visibilities after having selected the baselines, side bands and/or subbands needed. This is done via SET BASELINES, SET BANDS, SET SUBBANDS commands. Channel number should be specified as X axis and Phase and/or amplitude as Y axis, SET MODE SPEC. You should preferrably use SET PHASE CONTINUOUS, since $2 \pi$ jumps may occur in the passband shape. Then a calibration curve is determined by command SOLVE RF_PASSBAND. This command will fit a polynomial into each measured phase or amplitude, for each line subband. For the line subbands the polynomial is by default of degree 0 for amplitude and 1 for phase data. Higher degrees may be specified as arguments to the SOLVE RF_PASSBAND command. For the continuum, the ten values are simply stored and will be used as calibration data.

With option /PLOT, the curve will be plotted with the data points. The calibration curve is then in memory. These PLOT and SOLVE operations will have to be done in several steps, if many subbands are used. The curve for each subband and sideband is kept in memory, so that a single STORE command is needed.