The calibration process can be somewhat complicated, with several possible paths. We will describe only the main paths here. It is strongly recommended that you follow them. If you stray off them, there is usually a way ahead, but it may not be simple.
We will describe the calibration of data either with two ( XX , YY ) or all four ( XX , YY , XY , YX ) polarisation products. However when there are only two products, a number of the steps involved (usually involving gpcal ) can be skipped.
The recommended procedures for calibration has evolved with time, as our understanding of the instrument and problem has improved, and as new reduction software has been written. Previous versions of this manual suggested loading and flagging the data in AIPS , and that XY phase correction should be done using a special task (atxy ). We now recommend loading data into MIRIAD from the start and applying XY
phase corrections during the loading process. For those who may need it, an outline of preparing and flagging in AIPS is given in Appendix D.
Figure 11.1 gives a flow chart of the steps typically involved.
Figure 11.1: Flow chart to prepare for calibration in MIRIAD
.