sdgaincal

sdgaincal(infile, calmode='doublecircle', radius='', smooth=True, antenna='', field='', spw='', scan='', intent='', applytable='', interp='', spwmap='', outfile='', overwrite=False)[source]

MS SD gain calibration task

[Description] [Examples] [Development] [Details]

Parameters

infile (path) - name of input SD dataset (must be MS)
calmode (string=’doublecircle’) - gain calibration mode (“doublecircle”)
calmode = doublecircle
- radius (variant=’’) - radius of central region to be used for calibration
- smooth (bool=True) - smooth data or not
antenna (string=’’) - select data by antenna name or ID, e.g. “PM03”
field (string=’’) - select data by field IDs and names, e.g. “3C2*” (”” = all)
spw (string=’’) - select data by spw IDs (spectral windows), e.g., “3,5,7” (”” = all)
scan (string=’’) - select data by scan numbers, e.g. “21~23” (“”=all)
applytable (variant=’’) - (List of) sky and/or tsys tables for pre-application
applytable != ''
- interp (variant=’’) - Interp type in time[,freq], per gaintable. default==linear,linear
- spwmap (any=’’) - Spectral window mappings to form for applytable(s)
outfile (string=’’) - name of output caltable
overwrite (bool=False) - overwrite the output file if already exists [True, False]

Description

sdgaincal computes and removes a time-dependent gain variation in single-dish data on a per-spectral-window and per-antenna basis. Presently the task operates only on data taken with the ALMA fast-mapped, double-circle observation modes [1] . This task exploits the fact that the double-circle mode observes the same position in the center of the mapped field, approximately circular every sub-cycle, and normalizes the gains throughout the entire dataset, relative to the measured brightness at the center position.

Note

Info: This gain calibration task is done independently of, and following, the atmosphere (i.e. \(T_{sys}\)) and sky calibration steps applied through the sdcal task. Alternative way to apply these caltables is to utilize pre-application capability of sdgaincal task. This can be done by feeding caltables into the task using applytable parameter. You can specify spw mapping and interpolation method via spwmap and interp, respectively. Usage for these parameters are exactly same as applycal.

Configurable inputs control the calibration mode, selection parameters, and output behavior:

Presently, this task has only one calibration mode: calmode=’doublecircle’.

The size of the region that CASA regards as “the center” is user-configurable via the expandable ‘radius’ (in arcsec) parameter (under ‘calmode’). The default is to use the size of the primary beam. The data can also be smoothed in the time domain, prior to computation of the gain variation. Selection is by specral window/channels, field IDs, and antenna through the spw, field, and antenna selection parameters. The default is to use all data for the gain calibration. The caltable can be output with the ‘outfile’ parameter.

Bibliography

Examples

There are two ways to generate and apply double-circle gaintable. One is to calibrate and apply atmosphere and sky calibrations separately, and the other is to apply them on-the-fly during double-circle gain calibration. The latter should be more efficient. Examples for these two procedures are shown below.

Apply atmosphere and sky caltables separately

To compute a gaintable and subsequently apply it using applycal:

Generate the \(T_{sky}\) and \(T_{sys}\) calibration tables, and apply them (sdcal)
Split out the corrected column data (split)
Generate the double-circle gaincal calibration tables (sdgaincal)
Apply the double-circle gaincal calibration tables (applycal)

In CASA, this looks like the following:

sdcal(infile=inputvis, calmode='ps,tsys,apply')
split(vis=inputvis, outputvis=calibratedvis, datacolumn='corrected')
sdgaincal(infile=calibratedvis, outfile='DCgaintable', calmode='doublecircle')
applycal(vis=calibratedvis, gaintable='DCgaintable')

Apply atmosphere and sky caltables on-the-fly

To compute a gaintable and subsequently apply it using applycal:

Generate the \(T_{sky}\) and \(T_{sys}\) calibration tables (sdcal)
Generate the double-circle gaincal calibration tables by applying \(T_{sky}\) and \(T_{sys}\) calibration tables on-the-fly (sdgaincal)
- You can set spwmap and interp for each pre-application caltable if necessary
Apply the double-circle gaincal calibration tables (applycal)

In CASA, this looks like the following:

sdcal(infile=inputvis, calmode='ps', outfile='sky.tbl')
sdcal(infile=inputvis, calmode='tsys', outfile='tsys.tbl')
sdgaincal(infile=inputvis, applytable=['sky.tbl', 'tsys.tbl'],
          outfile='DCgaintable', calmode='doublecircle')
applycal(vis=inputvis, gaintable='DCgaintable')

Development: No additional development details

Parameter Details: Detailed descriptions of each function parameter

infile (path) - name of input SD dataset (must be MS)

calmode (string='doublecircle') - gain calibration mode

radius (variant='') - radius of central region to be used for calibration

smooth (bool=True) - smooth data or not

antenna (string='') - select data by antenna name or ID, e.g. “PM03”

field (string='') - select data by field IDs and names, e.g. “3C2*” (”” = all)

spw (string='') - select data by spw IDs (spectral windows), e.g., “3,5,7” (”” = all)

scan (string='') - select data by scan numbers, e.g. “21~23” (“”=all)

intent (string='') - select data by observation intent, e.g. “OBSERVE_TARGET#ON_SOURCE” (“”=all)

applytable (variant='') - (List of) sky and/or tsys tables for pre-application

interp (variant='') - Interp type in time[,freq], per gaintable. default==linear,linear

spwmap (any='') - Spectral window mappings to form for applytable(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

applytables)

outfile (string='') - name of output caltable

overwrite (bool=False) - overwrite the output file if already exists