Jupiter: continuum polarization calibration 5.5.0: Difference between revisions
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Set the absolute flux density scale, but only for Stokes I at the moment. Our primary (flux) calibrator here is 1331+305 (3C286). The default model for CASA 5.3+ is 'Perley-Butler 2017'. | Set the absolute flux density scale, but only for Stokes I at the moment. Our primary (flux) calibrator here is 1331+305 (3C286). The default model for CASA 5.3+ is 'Perley-Butler 2017'. | ||
<source lang="python"> | <source lang="python"> | ||
setjy(vis='jupiter6cm.demo.ms', field='1331+305') | setjy(vis='jupiter6cm.demo.ms', field='1331+305') | ||
</source> | </source> | ||
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Firstly generate an antenna zenith-angle dependent VLA gain curve calibration table | Firstly generate an antenna zenith-angle dependent VLA gain curve calibration table | ||
<source lang="python"> | <source lang="python"> | ||
gencal(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.gc', caltype='gc') | gencal(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.gc', caltype='gc') | ||
</source> | </source> | ||
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Now, solve for antenna gains on 1331+305 and 0137+331, using the just generated gain curve table (.gc). | Now, solve for antenna gains on 1331+305 and 0137+331, using the just generated gain curve table (.gc). | ||
<source lang="python"> | <source lang="python"> | ||
gaincal(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.G', field='1331+305,0137+331', spw='', gaintype='G', calmode='ap', solint='inf', combine='', refant='11', minsnr=3, gaintable=['jupiter6cm.demo.gc'], parang=False) | gaincal(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.G', field='1331+305,0137+331', spw='', gaintype='G', calmode='ap', solint='inf', combine='', refant='11', minsnr=3, gaintable=['jupiter6cm.demo.gc'], parang=False) | ||
# | # And check the solutions | ||
plotcal(caltable='jupiter6cm.demo.G', xaxis='time', yaxis='amp', subplot='333', iteration='antenna') | plotcal(caltable='jupiter6cm.demo.G', xaxis='time', yaxis='amp', subplot='333', iteration='antenna') | ||
</source> | </source> | ||
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If all looks good, bootstrap the flux density scale of the flux calibrator onto the phase calibrators. AIPS called it GETJY, but CASA calls it fluxscale. | If all looks good, bootstrap the flux density scale of the flux calibrator onto the phase calibrators. AIPS called it GETJY, but CASA calls it fluxscale. | ||
<source lang="python"> | <source lang="python"> | ||
myFluxscale = fluxscale(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.G', fluxtable='jupiter6cm.demo.Gflx', reference='1331+305', transfer='0137+331', append=False, display=False) | myFluxscale = fluxscale(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.G', fluxtable='jupiter6cm.demo.Gflx', reference='1331+305', transfer='0137+331', append=False, display=False) | ||
</source> | </source> | ||
The output is displayed in the logger as well as stored in the myFluxscale python dictionary | |||
<pre style="background-color: #fffacd;"> | |||
Beginning fluxscale--(MSSelection version)------- | |||
Found reference field(s): 1331+305 | |||
Found transfer field(s): 0137+331 | |||
Flux density for 0137+331 in SpW=0 (freq=4.8851e+09 Hz) is: 5.29882 +/- 0.00457512 (SNR = 1158.18, N = 54) | |||
Flux density for 0137+331 in SpW=1 (freq=4.8351e+09 Hz) is: 5.35056 +/- 0.00178254 (SNR = 3001.65, N = 54) | |||
Fitted spectrum for 0137+331 with fitorder=1: Flux density = 5.32463 +/- 0 (freq=4.86004 GHz) spidx=-0.944519 (degenerate) | |||
Storing result in jupiter6cm.demo.Gflx | |||
Writing solutions to table: jupiter6cm.demo.Gflx | |||
</pre> | |||
When executing fluxscale(), the calibration table with the extension .G is modified and stored as a new table with the extension .Gflx. So far, solutions have been generated only for the calibrators, and have not yet been transferred to the target source(s). | |||
Before proceeding, inspect the flux density calibration and save results to a file | |||
<source lang="python"> | |||
plotcal(caltable='jupiter6cm.demo.Gflx', xaxis='time', yaxis='amp', showgui=True, figfile='jupiter6cm.demo.Gflx.amp.png') | |||
plotcal(caltable='jupiter6cm.demo.Gflx', xaxis='time', yaxis='phase', plotrange=[-1,-1,-200,200], showgui=True, figfile='jupiter6cm.demo.Gflx.phase.png') | |||
</source> | |||
=== Polarisation calibration === | |||
Revision as of 14:23, 30 July 2018
Data Import
Data Inspection and Editing
Calibration
Set the Flux Scale
Set the absolute flux density scale, but only for Stokes I at the moment. Our primary (flux) calibrator here is 1331+305 (3C286). The default model for CASA 5.3+ is 'Perley-Butler 2017'.
setjy(vis='jupiter6cm.demo.ms', field='1331+305')
Initial gain calibration
At this stage the data have an overall flux density scaling determined, but full gain solutions aren't there yet. The relevant task is gaincal (analogous to the AIPS task CALIB). Rather than generate solution tables (SN tables in AIPS) that are attached to the measurement set (UVFITS in AIPS era), gaincal will produce a separate tables, and we will use appropriate extensions to keep track of what is what.
Firstly generate an antenna zenith-angle dependent VLA gain curve calibration table
gencal(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.gc', caltype='gc')
Now, solve for antenna gains on 1331+305 and 0137+331, using the just generated gain curve table (.gc).
gaincal(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.G', field='1331+305,0137+331', spw='', gaintype='G', calmode='ap', solint='inf', combine='', refant='11', minsnr=3, gaintable=['jupiter6cm.demo.gc'], parang=False)
# And check the solutions
plotcal(caltable='jupiter6cm.demo.G', xaxis='time', yaxis='amp', subplot='333', iteration='antenna')
If all looks good, bootstrap the flux density scale of the flux calibrator onto the phase calibrators. AIPS called it GETJY, but CASA calls it fluxscale.
myFluxscale = fluxscale(vis='jupiter6cm.demo.ms', caltable='jupiter6cm.demo.G', fluxtable='jupiter6cm.demo.Gflx', reference='1331+305', transfer='0137+331', append=False, display=False)
The output is displayed in the logger as well as stored in the myFluxscale python dictionary
Beginning fluxscale--(MSSelection version)------- Found reference field(s): 1331+305 Found transfer field(s): 0137+331 Flux density for 0137+331 in SpW=0 (freq=4.8851e+09 Hz) is: 5.29882 +/- 0.00457512 (SNR = 1158.18, N = 54) Flux density for 0137+331 in SpW=1 (freq=4.8351e+09 Hz) is: 5.35056 +/- 0.00178254 (SNR = 3001.65, N = 54) Fitted spectrum for 0137+331 with fitorder=1: Flux density = 5.32463 +/- 0 (freq=4.86004 GHz) spidx=-0.944519 (degenerate) Storing result in jupiter6cm.demo.Gflx Writing solutions to table: jupiter6cm.demo.Gflx
When executing fluxscale(), the calibration table with the extension .G is modified and stored as a new table with the extension .Gflx. So far, solutions have been generated only for the calibrators, and have not yet been transferred to the target source(s).
Before proceeding, inspect the flux density calibration and save results to a file
plotcal(caltable='jupiter6cm.demo.Gflx', xaxis='time', yaxis='amp', showgui=True, figfile='jupiter6cm.demo.Gflx.amp.png')
plotcal(caltable='jupiter6cm.demo.Gflx', xaxis='time', yaxis='phase', plotrange=[-1,-1,-200,200], showgui=True, figfile='jupiter6cm.demo.Gflx.phase.png')
Polarisation calibration
Template:Checked 5.3.0
