Documentation on gplist

Task: gplist
Purpose: List gains table and optionally overwrite calibration
Categories: calibration

     GpList is a Miriad task to list the amplitude gains in a gains table
     and (optionally) replace the amplitude information in a gains
     table with constants of the users choosing, and/or simultaneously 
        setting the phase corrections to zero.

     WARNING: if you modify the gains, the resulting amplitude gains will be 
              constant with time! The original gains table is overwritten.

     The motivation for this routine arose from datasets in which the
     calibrator is weak so that conventional amplitude calibration was not
     very successful. This was compounded by antenna 3 being blown about 
     by the wind. The source, on the other hand, was strong but time
     variable, hence not susceptible to self-cal. From observations of
     strong planets before and after it was observed that the amplitude
     scale was reasonably stable, and certainly more stable than implied
     by the phase-calibrator data, so that only phase calibration really needs
     to be applied to the source. This program allows the amplitude scale
     to be forced to the desired values (in this case, obtained from the
     planet observations) without changing the phase calibration.

Key: vis
     The input visibility file, containing the gain file to list/massage

Key: options
       amp      List the amplitude gains for 9 antennas: default option
       phase    List the phase corrections for 9 antennas.
       complex  List complex gains for current 6 ants only (1 line per soln)
       all      List all complex gains (one line per antenna per solution
                for 9 antennas; lots of output)
       replace  Replace the amplitude gains with the list supplied 
                Only antennas with non-zero values in the list are affected
                so if jyperk is not set, nothing happens. Phases are
                preserved unless options=zerophas is also specified
       multiply Multiply existing sqrt(Jy/K) values in a gains table by
                the list supplied in the jyperk variable. Only antennas
                corresponding to nonzero jyperk elements are changed.
                No effect on phases.
       zerophas Zero all phase corrections (no antenna selection method)

       Use options=replace,zerophas with suitable jyperk list to 
       both set amp scale and zero phases (the two steps are 
       carried out sequentially with the amplitudes being set first)

Key: jyperk
     Array of 12 numbers (1 per antenna) giving the Jy-per-K values.
     Array elements default to zero so you don't have to give 12 numbers.
     Action will only be taken for antennas corresponding to nonzero 
     elements of jyperk.
     Used for options=replace or options=multiply. For options=replace,
     if any of the numbers are zero then the amp gains in the pre-existing
     table will not be changed, so you can change the gains on a single
     antennna without changing the others by setting all the other
     values to zero. However, be aware that your one bad antenna will
     have affected the solutions for the other antennas as well.
     Typical values at 86 GHz are (1995 Feb):
            jyperk=14.0,0.0,10.5,11.5,10.5,13.0,11.0,0.0,0.0
     For options=multiply, jyperk supplies a list of multiplication
     factors (one per antenna) which will be used to multiply the 
     sqrt(Jy/K) amplitude gains in the existing table.