gaincal – Determine temporal gains from calibrator observations – calibration task
Description
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.
Parameters
Parameter |
Default |
Description |
|---|---|---|
vis |
|
Name of input visibility file |
caltable |
|
Name of output gain calibration table |
field |
|
Select field using field id(s) or field name(s) |
spw |
|
Select spectral window/channels |
intent |
|
Select observing intent |
selectdata |
|
Other data selection parameters |
timerange |
|
Select data based on time range |
uvrange |
|
Select data by baseline length. |
antenna |
|
Select data based on antenna/baseline |
scan |
|
Scan number range |
observation |
|
Select by observation ID(s) |
msselect |
|
Optional complex data selection (ignore for now) |
solint |
|
Solution interval |
combine |
|
Data axes which to combine for solve (obs, scan, spw, and/or field) |
preavg |
|
Pre-averaging interval (sec) (rarely needed) |
refant |
|
Reference antenna name(s) |
refantmode |
|
Reference antenna mode |
minblperant |
|
Minimum baselines _per antenna required for solve |
minsnr |
|
Reject solutions below this SNR |
solnorm |
|
Normalize (squared) solution amplitudes (G, T only) |
normtype |
|
Solution normalization calculation type: mean or median |
gaintype |
|
Type of gain solution (G,T,GSPLINE,K,KCROSS) |
smodel |
|
Point source Stokes parameters for source model. |
calmode |
|
Type of solution” ('ap', 'p', 'a') |
solmode |
|
Robust solving mode: ('', 'L1', 'R','L1R') |
rmsthresh |
|
RMS Threshold sequence (for solmode='R' or 'L1R'; see help) |
corrdepflags |
|
Respect correlation-dependent flags |
append |
|
Append solutions to the (existing) table |
splinetime |
|
Spline timescale(sec); All spw's are first averaged. |
npointaver |
|
The phase-unwrapping algorithm |
phasewrap |
|
Wrap the phase for jumps greater than this value (degrees) |
docallib |
|
Use callib or traditional cal apply parameters |
callib |
|
Cal Library filename |
gaintable |
|
Gain calibration table(s) to apply on the fly |
gainfield |
|
Select a subset of calibrators from gaintable(s) |
interp |
|
Interpolation parameters for each gaintable, as a list |
spwmap |
|
Spectral window mappings to form for gaintable(s) |
parang |
|
Apply parallactic angle correction |
Parameter Explanations
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’
field
''
- Select field using field id(s) or field name(s)
Default: ‘’ (all fields)
Use ‘go listobs’ to obtain the list id’s or names. If field string is a non-negative integer, it is assumed a field index, otherwise, it is assumed a field name.
Examples: 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
spw
''
- Select spectral window/channels
Default: ‘’ (all spectral windows and channels)
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
intent
''
- Select observing intent
Default: ‘’ (no selection by intent)
Example: intent=’BANDPASS’ (selects data labelled with BANDPASS intent)
selectdata
True
- Other data selection parameters
Default: True Options: True|False
timerange
''
- Select data based on time range
Subparameter of selectdata=True 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 by baseline length.
Default = ‘’ (all)
Examples: uvrange=’0~1000klambda’; uvrange from 0-1000 kilo-lambda uvrange=’>4klambda’;uvranges greater than 4 kilo-lambda uvrange=’0~1000km’; uvrange in kilometers
antenna
''
- Select data based on antenna/baseline
Subparameter of selectdata=True Default: ‘’ (all)
If antenna string is a non-negative integer, it is assumed an antenna index, otherwise, it is assumed as an antenna name
Examples: 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
Subparameter of selectdata=True Default: ‘’ = all
Check ‘go listobs’ to insure the scan numbers are in order.
observation
''
- Select by observation ID(s)
Subparameter of selectdata=True Default: ‘’ = all
Example: observation=’0~2,4’
msselect
''
Optional complex data selection (ignore for now)
solint
'inf'
- Solution interval
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 (i.e., 1 minute); solint=’0s’; solint=0; solint=’int’ (i.e., per integration); solint-‘-1s’; solint=’inf’ (i.e., ~infinite, up to boundaries enforced by combine)
combine
''
- Data axes which to combine for solve
Default: ‘scan’ (solutions will break at obs, field, and spw boundaries) Options: ‘’,’obs’,’scan’,’spw’,field’, or any comma-separated combination in a single string
Example: combine=’scan,spw’ - Extend solutions over scan boundaries (up to the solint), and combine spws for solving
preavg
float(-1.0)
- Pre-averaging interval (sec)
Default: -1.0 (none)
Rarely needed. Will average data over periods shorter than the solution interval first.
refant
''
Reference antenna name(s); a prioritized list may be specified
Default: ‘’ (No refant applied)
Examples: refant=’4’ (antenna with index 4) refant=’VA04’ (VLA antenna #4) refant=’EA02,EA23,EA13’ (EVLA antenna EA02, use EA23 and EA13 as alternates if/when EA02 drops out)
Use taskname=listobs for antenna listing
refantmode
'flex'
Reference antenna mode
minblperant
int(4)
Minimum number of baselines required per antenna for each solve
Default: 4
Antennas with fewer baselines 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
float(3.0)
- Reject solutions below this SNR
Default: 3.0
solnorm
False
- Normalize (squared) solution amplitudes (G, T only)
Default: False (no normalization)
normtype
'mean'
- Solution normalization calculation type: mean or median
Default: ‘mean’
gaintype
'G'
- Type of gain solution (G,T,GSPLINE,K,KCROSS)
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.
‘K’ solves for simple antenna-based delays via FFTs of the spectra on baselines to the reference antenna. (This is not global fringe-fitting.) If combine includes ‘spw’, multi-band delays are determined; otherwise, per-spw single-band delays will be determined.
‘KCROSS’ solves for a global cross-hand delay. Use parang=T and apply prior gain and bandpass solutions. Multi-band delay solves (combine=’spw’) not yet supported for KCROSS.
smodel
numpy.array( [ ] )
Point source Stokes parameters for source model (experimental).
Default: [] (use MODEL_DATA column)
Example: [1,0,0,0] (I=1, unpolarized)
calmode
'ap'
- Type of solution” (‘ap’, ‘p’, ‘a’)
Default: ‘ap’ (amp and phase) Options: ‘p’ (phase) ,’a’ (amplitude), ‘ap’ (amplitude and phase)
Example: calmode=’p’
solmode
''
- Robust solving mode:
Options: ‘’, ‘L1’, ‘R’, ‘L1R’
rmsthresh
numpy.array( [ ] )
- RMS Threshold sequence
Subparameter of solmode=’R’ or ‘L1R’
See CASA Docs for more information (https://casa.nrao.edu/casadocs/)
corrdepflags
False
- If False (default), if any correlation is flagged, treat all correlations in
the visibility vector as flagged when solving (per channel, per baseline). If True, use unflagged correlations in a visibility vector, even if one or more other correlations are flagged.
Default: False (treat correlation vectors with one or more correlations flagged as entirely flagged)
Traditionally, CASA has observed a strict interpretation of correlation-dependent flags: if one or more correlations (for any baseline and channel) is flagged, then all available correlations for the same baseline and channel are treated as flagged. However, it is desirable in some circumstances to relax this stricture, e.g., to preserve use of data from antennas with only one good polarization (e.g., one polarization is bad or entirely absent). Solutions for the bad or missing polarization will be rendered as flagged.
append
False
- Append solutions to the (existing) table
Default: False (overwrite existing table or make new table)
Appended solutions must be derived from the same MS as the existing caltable, and solution spws must have the same meta-info (according to spw selection and solint) or be non-overlapping.
splinetime
float(3600.0)
- Spline timescale(sec); All spw's are first averaged.
Subparameter of gaintype=’GSPLINE’ Default: 3600 (1 hour)
Example: splinetime=1000
Typical splinetime should cover about 3 to 5 calibrator scans.
npointaver
int(3)
- Tune phase-unwrapping algorithm
Subparameter of gaintype=’GSPLINE’ Default: 3; Keep at this value
phasewrap
float(180.0)
Wrap the phase for jumps greater than this value (degrees)
Subparameter of gaintype=’GSPLINE’ Default: 180; Keep at this value
docallib
False
- Control means of specifying the caltables
Default: False (Use gaintable, gainfield, interp, spwmap, calwt) Options: False|True
If True, specify a file containing cal library in callib
callib
''
- Specify a file containing cal library directives
Subparameter of docallib=True
gaintable
numpy.array( [ ] )
- Gain calibration table(s) to apply on the fly
Default: ‘’ (none) Subparameter of docallib=False
Examples: gaintable=’ngc5921.gcal’ gaintable=[‘ngc5921.ampcal’,’ngc5921.phcal’]
gainfield
numpy.array( [ ] )
- Select a subset of calibrators from gaintable(s)
Default: ‘’ (all sources on the sky)
‘nearest’ ==> nearest (on sky) available field in table otherwise, same syntax as field
Examples: gainfield=’0~2,5’ means use fields 0,1,2,5 from gaintable gainfield=[‘0~3’,’4~6’] means use field 0 through 3
interp
numpy.array( [ ] )
- Interpolation parmameters (in time[,freq]) for each gaintable, as a list of strings.
Default: ‘’ –> ‘linear,linear’ for all gaintable(s) Options: Time: ‘nearest’, ‘linear’
Freq: ‘nearest’, ‘linear’, ‘cubic’, ‘spline’
Specify a list of strings, aligned with the list of caltable specified in gaintable, that contain the required interpolation parameters for each caltable. * When frequency interpolation is relevant (B, Df,
Xf), separate time-dependent and freq-dependent interp types with a comma (freq_after_ the comma).
Specifications for frequency are ignored when the calibration table has no channel-dependence.
Time-dependent interp options ending in ‘PD’ enable a “phase delay” correction per spw for non-channel-dependent calibration types.
For multi-obsId datasets, ‘perobs’ can be appended to the time-dependent interpolation specification to enforce obsId boundaries when interpolating in time.
Freq-dependent interp options can have ‘flag’ appended to enforce channel-dependent flagging, and/or ‘rel’ appended to invoke relative frequency interpolation
Examples: interp=’nearest’ (in time, freq-dep will be linear, if relevant) interp=’linear,cubic’ (linear in time, cubic in freq) interp=’linearperobs,splineflag’ (linear in time per obsId, spline in freq with channelized flagging) interp=’nearest,linearflagrel’ (nearest in time, linear in freq with with channelized flagging and relative-frequency interpolation) interp=’,spline’ (spline in freq; linear in time by default) interp=[‘nearest,spline’,’linear’] (for multiple gaintables)
spwmap
[ ]
- Spectral window mappings to form for gaintable(s)
Only used if callib=False default: [] (apply solutions from each calibration spw to
the same MS spw only)
- Any available calibration spw can be mechanically mapped to any
MS spw.
- Examples:
- spwmap=[0,0,1,1] means apply calibration
from cal spw = 0 to MS spw 0,1 and cal spw 1 to MS spws 2,3.
- spwmap=[[0,0,1,1],[0,1,0,1]] (use a list of lists for multiple
gaintables)
parang
False
- Apply parallactic angle correction
Default: False
If True, apply the parallactic angle correction (required for polarization calibration)