PSRCHIVE User's Guide: Overview of Calibration

The progam pac calibrates pulsar data using available combinations of:
  1. polarimetric calibrator observations as described in Appendix A of the pac manual.
  2. flux calibration solutions as output by fluxcal;
  3. a reception model (including cross-coupling parameters) as output by pcm [required only when the pac -S command line option is used]
pcm is used to produce a reception model, but it will also output calibrated versions of its input files (which should be uncalibrated). These calibrated outputs are useful as diagnostics, but they will also be calibrated using a model that includes any time variations (e.g. if the pcm -u or -o options are used). If these options are used, and a better fit is obtained, then the calibrated output from pcm will be better than that output by pac, but only for the data set used as input; the time variations do not apply to any other pulsar and they are not stored in the solution output by pcm (a PSRFITS file named pcm.fits).

If a pcm.fits solution has been derived from other data, and it has the same instrumental parameters listed in database.txt, then pac can apply the model stored in pcm.fits to calibrate the pulsar data. It is not necessary to use pcm to calibrate data (unless time variations produce a better fit to the data, and the data to be calibrated are those used as input to pcm, as mentioned above).