Bandpass calibration

In the calibration procedure bandpass normalisation by the auto-correlation functions of the antennas is applied (visibilities on a baseline are divided by the square root of the autocorrelation function of each antenna). The correlator's intrinsic phase bandpass is removed with the dedicated OBS $\backslash$BANDPASS procedure. Except possibly for very narrow spectral bands, a bandpass calibration with a celestial source is still necessary to compensate for receiver|cable|antenna induced phase slopes.

No specific procedure is required as this is only a long integration on a strong continuum source (not necessarily a point source). The phase calibrator may even be used for such a measurement. A qualifier is available in the Date.IPB file to identify bandpass calibrator observations; this information comes from the OBS $\backslash$SOURCE command in the OBS program (option /TYPE BANDPASS. The qualifier is then used by CLIC for data reduction. Bandpass calibration can be applied to observation of other sources within CLIC using the CLIC $\backslash$SOLVE RF_PASSBAND command.