next up previous contents index
Next: Storing the Phase Calibration Up: Phase Calibration Previous: Phase Calibration   Contents   Index

Determining the calibration curve

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. Time should be specified as X axis and Phase as Y axis (in SET MODE TIME, of course). SET PHASE CONTINUOUS should also be specified, otherwise fitting a smooth curve will be difficult.

Then a calibration curve is determined by command SOLVE PHASE. By default this command will fit a cubic spline into each measured phase or amplitude. With option /PLOT, the curve will be plotted with the data points. The calibration curve is then in memory.

The time interval between knots of the cubic splines is available as a parameter through the SET STEP command. Its default value is 3 hours. Additional knots may be introduced with the option /BREAK, to match discontinuities or angular points.

Alternatively, with option /POLYNOMIAL, a polynomial fit will be made. The degree of the polynomial is automatically chosen, using the statistical errors bars for each data point.


next up previous contents index
Next: Storing the Phase Calibration Up: Phase Calibration Previous: Phase Calibration   Contents   Index
Gildas manager 2018-08-17