Gaincal
From CASA Guides
Jump to navigationJump to search
Help on gaincal task:
Determine temporal gains from calibrator observations
The complex gains for each antenna/spwid are determined from the
data column (raw data) divided by the model column. The gains can
be obtained for a specified solution interval, spw combination and
field combination. The GSPLINE spline (smooth) option is still under
development.
Previous calibrations (egs, bandpass, opacity, parallactic angle) can
be applied on the fly. At present with dual-polarized data, both
polarizations must be unflagged for any solution to be obtained.
Keyword arguments:
vis -- Name of input visibility file
default: none; example: vis='ngc5921.ms'
caltable -- Name of output gain calibration table
default: none; example: caltable='ngc5921.gcal'
--- Data Selection (see help par.selectdata for more detailed information)
field -- Select field using field id(s) or field name(s).
['go listobs' to obtain the list id's or names]
default: ''=all fields
If field string is a non-negative integer, it is assumed a
field index, otherwise, it is assumed a field name
field='0~2'; field ids 0,1,2
field='0,4,5~7'; field ids 0,4,5,6,7
field='3C286,3C295'; field named 3C286 and 3C295
field = '3,4C*'; field id 3, all names starting with 4C
DON'T FORGET TO INCLUDE THE FLUX DENSITY CALIBRATOR IF YOU HAVE ONE
spw -- Select spectral window/channels
type 'help par.selection' for more examples.
spw='0~2,4'; spectral windows 0,1,2,4 (all channels)
spw='<2'; spectral windows less than 2 (i.e. 0,1)
spw='0:5~61'; spw 0, channels 5 to 61, INCLUSIVE
spw='*:5~61'; all spw with channels 5 to 61
spw='0,10,3:3~45'; spw 0,10 all channels, spw 3, channels 3 to 45.
spw='0~2:2~6'; spw 0,1,2 with channels 2 through 6 in each.
spw='0:0~10;15~60'; spectral window 0 with channels 0-10,15-60
NOTE ';' to separate channel selections
spw='0:0~10^2,1:20~30^5'; spw 0, channels 0,2,4,6,8,10,
spw 1, channels 20,25,30
selectdata -- Other data selection parameters
default: True
timerange -- Select data based on time range:
default = '' (all); examples,
timerange = 'YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss'
Note: if YYYY/MM/DD is missing date defaults to first day in data set
timerange='09:14:0~09:54:0' picks 40 min on first day
timerange= '25:00:00~27:30:00' picks 1 hr to 3 hr 30min on NEXT day
timerange='09:44:00' pick data within one integration of time
timerange='>10:24:00' data after this time
uvrange -- Select data within uvrange (default units meters)
default: '' (all); example:
uvrange='0~1000klambda'; uvrange from 0-1000 kilo-lambda
uvrange='>4klambda';uvranges greater than 4 kilo lambda
antenna -- Select data based on antenna/baseline
default: '' (all)
If antenna string is a non-negative integer, it is assumed an
antenna index, otherwise, it is assumed as an antenna name
antenna='5&6'; baseline between antenna index 5 and index 6.
antenna='VA05&VA06'; baseline between VLA antenna 5 and 6.
antenna='5&6;7&8'; baselines with indices 5-6 and 7-8
antenna='5'; all baselines with antenna index 5
antenna='05'; all baselines with antenna number 05 (VLA old name)
antenna='5,6,10'; all baselines with antennas 5,6,10 index numbers
scan -- Scan number range.
Check 'go listobs' to insure the scan numbers are in order.
msselect -- Optional complex data selection (ignore for now)
--- Solution parameters
gaintype -- Type of gain solution (G, T, or GSPLINE)
default: 'G'; example: gaintype='GSPLINE'
'G' means determine gains for each polarization and sp_wid
'T' obtains one solution for both polarizations; Hence. their
phase offset must be first removed using a prior G.
'GSPLINE' makes a spline fit to the calibrator data. It is
useful for noisy data and fits a smooth curve through the
calibrated amplitude and phase. However,
at present GSPLINE is somewhat experimental. Use with
caution and check solutions.
calmode -- Type of solution
default: 'ap' (amp and phase); example: calmode='p'
Options: 'p','a','ap'
solint -- Solution interval (units optional)
default: 'inf' (~infinite, up to boundaries controlled by combine);
Options: 'inf' (~infinite),
'int' (per integration)
any float or integer value with or without units
examples: solint='1min'; solint='60s'; solint=60 --> 1 minute
solint='0s'; solint=0; solint='int' --> per integration
solint-'-1s'; solint='inf' --> ~infinite, up to boundaries
interacts with combine
combine -- Data axes to combine for solving
default: '' --> solutions will break at scan, field, and spw
boundaries
Options: '','scan','spw',field', or any comma-separated combination
example: combine='scan,spw' --> extend solutions over scan boundaries
(up to the solint), and combine spws for solving
refant -- Reference antenna name
default: '' => refant = '0' (may not be a good choice)
example: refant='4' (antenna with index 4)
refant='VA04' (VLA antenna #4)
Use taskname=listobs for antenna listing
minblperant -- Minimum number of baselines required per antenna for each solve
default = 4
Antennas with fewer baaselines are excluded from solutions.
example: minblperant=10 => Antennas participating on 10 or more
baselines are included in the solve
minblperant = 1 will solve for all baseline pairs, even if only
one is present in the data set. Unless closure errors are
expected, use taskname=gaincal rather than taskname=blcal to
obtain more options in data analysis.
minsnr -- Reject solutions below this SNR
default: 0.0 (accept all attempted solutions)
solnorm -- Normalize average solution amps to 1.0 after solution (G, T only)
default: False (no normalization)
append -- Append solutions to the (existing) table
default: False; overwrite existing table or make new table
splinetime -- Spline timescale (sec); used for gaintype='GSPLINE'
default: 3600 (1 hour); example: splinetime=1000
Typical splinetime should cover about 3 to 5 calibrator scans.
npointaver -- Tune phase-unwrapping algorithm for gaintype='GSPLINE'
default: 3; Keep at this value
phasewrap -- Wrap the phase for changes larger than this amoun (degrees)
default: 180; Keep at this value
--- Other calibrations to apply on the fly before determining gaincal solution
gaintable -- Gain calibration table(s) to apply
default: '' (none);
examples: gaintable='ngc5921.gcal'
gaintable=['ngc5921.ampcal','ngc5921.phcal']
gainfield -- Select a subset of calibrators from gaintable(s) to apply
default:'' ==> all sources in table;
same syntax as field
example: gainfield='0~2,5' means use fields 0,1,2,5 from gaintable
gainfield=['0~3','4~6'] means use field 0 through 3
from first gain file, field 4 through 6 for second.
interp -- Interpolation mode (in time) to use for each gaintable
default: '' --> 'linear' for all gaintable(s)
example: interp='nearest'
append -- Append solutions to the (existing) table
default: False; overwrite existing table or make new table
splinetime -- Spline timescale (sec); used for gaintype='GSPLINE'
default: 3600 (1 hour); example: splinetime=1000
Typical splinetime should cover about 3 to 5 calibrator scans.
npointaver -- Tune phase-unwrapping algorithm for gaintype='GSPLINE'
default: 3; Keep at this value
phasewrap -- Wrap the phase for changes larger than this amoun (degrees)
default: 180; Keep at this value
--- Other calibrations to apply on the fly before determining gaincal solution
gaintable -- Gain calibration table(s) to apply
default: '' (none);
examples: gaintable='ngc5921.gcal'
gaintable=['ngc5921.ampcal','ngc5921.phcal']
gainfield -- Select a subset of calibrators from gaintable(s) to apply
default:'' ==> all sources in table;
same syntax as field
example: gainfield='0~2,5' means use fields 0,1,2,5 from gaintable
gainfield=['0~3','4~6'] means use field 0 through 3
from first gain file, field 4 through 6 for second.
interp -- Interpolation mode (in time) to use for each gaintable
default: '' --> 'linear' for all gaintable(s)
example: interp='nearest'
interp=['nearest','linear']
Options: 'nearest', 'linear', 'aipslin'
spwmap -- Spectral windows combinations to form for gaintable(s)
default: [] (apply solutions from each spw to that spw only)
Example: spwmap=[0,0,1,1] means apply the caltable solutions
from spw = 0 to the spw 0,1 and spw 1 to spw 2,3.
spwmap=[[0,0,1,1],[0,1,0,1]]
gaincurve -- Apply internal VLA antenna gain curve correction (True/False)
default: False;
Use gaincurve=True ONLY for VLA data
opacity -- Opacity correction to apply (nepers)
default: 0.0 (no opacity correction)
example: opacity=0.051
Typical VLA values are: 5 GHz - 0.013, 8 GHz - 0.013
15 GHz - 0.016, 23 GHz - 0.051, 43 GHz - 0.07
preavg -- Pre-averaging interval (sec)
default=-1 (none).
Rarely needed. Will average data over periods shorter than
the solution interval first.
async -- Run asynchronously
default = False; do not run asychronously
