2.1.1.0 calibrater.linpolcor

NRAO Home > CASA > CASA Toolkit Reference Manual

calibrater.linpolcor - Function

2.1.1 Correct the gain table for linear polarization of the calibrator

Description

THIS METHOD IS CURRENTLY DISABLED.

This function can be used to correct the gains derived from secondary calibrators with unknown or variable polarization. It should only be used for arrays with linear (X/Y) feeds and an Alt-Az mount for which the observed polarization varies with feed position angle on the sky.

The function fits the gains with a sine and cosine term in feed position angle and extracts the Q and U components of the secondary calibrator. This is only possible if there is sufficient range in the position angle (i.e., minimum of about 6 scans spanning at least 90 degrees in position angle). Check the error of the fit to judge if the fit was succesfull, it should generally be smaller than 0.5%.

Use the fields argument to select calibrator fields to be fitted. The function takes a calibration table as input, and can write the adjusted gain solutions to the same table on output, or create a new table containing these results. The function also prints the derived polarization for each field for each spectral window.

Arguments


Inputs
tablein	Input calibration table name
	allowed:	string
	Default:
tableout	Output calibration table name
	allowed:	string
	Default:
fields	Calibrator field names
	allowed:	stringArray
	Default:

Returns
bool

Example

cb.open(’atca.ms’);
cb.linpolcor(tablein=’atca.gcal’, tableout=’atca.gcal2’,
fields=’2254-367’);
cb.close();

This example takes an existing calibration table containing {\tt G}
Jones matrices, and writes a corrected output table, correcting only
gains derived from 2254-367 for linear polarization.

__________________________________________________________________

[next] [prev] [prev-tail] [front] [up]

More information about CASA may be found at the CASA web page

This code is available under the terms of the GNU General Public Lincense