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Basic Information 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 BIMA datasets in which the
calibrator is weak so that conventional amplitude calibration was not
very successful. This was compounded by old BIMA ant3 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.
This routine is specific to CARMA, hardcoded for 15 antennae.
Key: vis
The input visibility file, containing the gain file to list/massage
Key: options
amp List the amplitude gains: default option
The mean, median and rms (about the mean) are reported.
phase List the phase corrections.
complex List complex gains for 10 antennas only (2 lines per soln)
all List all complex gains (one line per antenna per solution
for all antennas; lots of output, better than
options=complex if you want to grep one one antenna.)
replace Replace the amplitude gains with the list supplied
Unless OPTIONS=FORCE is also set, 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
force If set, then all values in jyperk are enforced when
doing a replace, even if they (or the initial gains)
are zero
limit Impose an upper limit on the amplitude gains using the
list specified in jyperk
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)
addphase Correct gains by antenna based phases supplied in the
jyperk array, units degrees. Note that these phases
are added to the existing phase gains, except when
OPTIONS=ZEROPHAS is also used.
clip Set to zero all gains outside range jyperk(1),jyperk(2)
Useful for pseudo-flagging of bad data, e.g.,
gplist vis=dummy options=clip jyperk=0.5,2.0
effectively flags data with gains outside 0.5-2 (default
range). However, data are not really flagged. The next
option is an alternative "flagging" option.
sigclip Set to zero all gains more than jyperk(1)*rms away from
median on each antenna
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)
Use options=addphase to add phases to the existing ones.
Use options=addphase,force to replace phases.
Key: ants=
If given, this is the list of ants you want to see displayed.
Useful if you want a less wide screen display.
By default all are displayed, within limits.
Key: jyperk
Array of 15 numbers (1 per antenna) giving the Jy-per-K values.
Array elements default to zero so you don't have to give 15 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.
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.