Applying the full calibration

  To apply the full calibration to the data, use the task SPLIT as one would for VLA data. This creates a single source format file which is then self calibrated and imaged. SPLIT can also be used to average across each IF and across the band, if so desired.

There are a few things to note about applying the full calibration. Before any self calibration or instrumental polarization calibration has been applied, average the data across each IF, but not in frequency. This means setting APARM(1)=1. Set APARM(2) equal to the integration time of the data out of the correlator. This enables ${\cal AIPS}$ to apply baseline amplitude corrections to the data to compensate for having averaged the data in frequency and time in the presence of residual delays and rates. Optionally, one may set APARM(4)=1 to calibrate the data weights. The effect of this is to divide the weights by the amplitude calibration factor. This way, the effects of bad or noisy antennas are reduced. To reduce the size of the data set, and to increase the signal to noise of the visibilities, the data should be averaged in time, say, to 10-15 seconds.

If the instrumental polarization parameters have already been determined (§ 3.8), they should not be applied at this point. Within the ${\cal AIPS}$ calibration scheme, the instrumental gain terms must be removed from the data before the instrumental polarization can be applied. This means the data must be reasonably well self calibrated before applying the D -terms. For this reason, the data should not be averaged across the entire band; full averaging in frequency should be done only after correction for instrumental polarization. Applying the polarization calibration is described in § 3.8.1.