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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.  
 

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