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

Title
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	`True`	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	`'inf'`	Solution interval
combine	`''`	Data axes which to combine for solve (obs, scan, spw, and/or field)
preavg	`float(-1.0)`	Pre-averaging interval (sec) (rarely needed)
refant	`''`	Reference antenna name(s)
refantmode	`'flex'`	Reference antenna mode
minblperant	`int(4)`	Minimum baselines _per antenna required for solve
minsnr	`float(3.0)`	Reject solutions below this SNR
solnorm	`False`	Normalize (squared) solution amplitudes (G, T only)
normtype	`'mean'`	Solution normalization calculation type: mean or median
gaintype	`'G'`	Type of gain solution (G,T,GSPLINE,K,KCROSS)
smodel	`numpy.array( [ ] )`	Point source Stokes parameters for source model.
calmode	`'ap'`	Type of solution” ('ap', 'p', 'a')
solmode	`''`	Robust solving mode: ('', 'L1', 'R','L1R')
rmsthresh	`numpy.array( [ ] )`	RMS Threshold sequence (for solmode='R' or 'L1R'; see help)
append	`False`	Append solutions to the (existing) table
splinetime	`float(3600.0)`	Spline timescale(sec); All spw's are first averaged.
npointaver	`int(3)`	The phase-unwrapping algorithm
phasewrap	`float(180.0)`	Wrap the phase for jumps greater than this value (degrees)
docallib	`False`	Use callib or traditional cal apply parameters
callib	`''`	Cal Library filename
gaintable	`numpy.array( [ ] )`	Gain calibration table(s) to apply on the fly
gainfield	`numpy.array( [ ] )`	Select a subset of calibrators from gaintable(s)
interp	`numpy.array( [ ] )`	Temporal interpolation for each gaintable (‘’=linear)
spwmap	`numpy.array( [ ] )`	Spectral windows combinations to form for gaintables(s)
parang	`False`	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/)

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 type (in time[,freq]) to use for each gaintable.

Default: ‘’ –> ‘linear,linear’ for all gaintable(s) Options: Time: ‘nearest’, ‘linear’

Freq: ‘nearest’, ‘linear’, ‘cubic’, ‘spline’

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.

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=’,spline’ (spline in freq; linear in time by default) interp=[‘nearest,spline’,’linear’] (for multiple gaintables)

spwmap

numpy.array( [ ] )

Spectral windows combinations to form for gaintables(s): Subparameter of callib=False default: [] (apply solutions from each spw to that spw only)

Examples: 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]] (for multiple gaintables)

parang

False

Apply parallactic angle correction

Default: False

If True, apply the parallactic angle correction (required for polarization calibration)