Solving for complex gain, bandpass and leakage

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Next: Correcting the gains for polarization of the calibrators Up: Basic Calibration Fundamentals Previous: Setting the calibration source model

Solving for complex gain, bandpass and leakage

The individual calibration effects in the ME, which are expressed as Jones matrices, are described in the Synthesis Calibration chapter of Getting Results, and the reader is referred there for a more detailed discussion. Each Jones matrix has a specific type; the complex electronic gain is the G Jones component, the bandpass gain is the B Jones component and the polarization leakage is the D Jones component.

For ATCA data with 4 polarizations you will want to solve for G, D and B. If you have spectral-line data with only 1 or 2 polarizations, then you need solve for G and B only. You can solve for more than one spectral window at a time. Solving for D Jones with XX/YY only data will not do anything useful, but generally won't harm either.

First solve for G, D and B Jones using the primary calibrator:

cal := calibrater('atca.ms')                    # Create a calibrater tool
cal.setdata(msselect='FIELD_ID==1')             # Select the primary calibrator (in this case id=1)
cal.setapply(type='P', t=10.0);                 # Correct for parallactic angle with 10 sec sampling.
cal.setsolve(type='G', t=30.0, table='cal.G')   # Solve for G Jones in 30 sec intervals
cal.setsolve(type='B', t=1.e6, table='cal.B')   # Solve for B Jones with an interval larger than your observation
cal.setsolve(type='D', t=1.e6, table='cal.D')   # Solve for D Jones with an interval larger than your observation
cal.solve();                                    # Do the actual solution
cal.plotcal(tablename='cal.G');                 # Plot the calibration solution obtained
cal.done()                                      # Destroy the calibrater tool

Now solve for the G Jones term using the secondary calibrator(s), e.g.:

cal := calibrater('atca.ms')                           # Create a new calibrater tool
cal.setdata(msselect='FIELD_ID==2')                    # Select the secondary calibrator (in this case id=2)
cal.setapply(type='P', t=10.0)                         # Correct for parallactic angle with 10 sec sampling.
cal.setapply(type='B', table='cal.B')                  # Apply B Jones solved for on primary
cal.setapply(type='D', table='cal.D')                  # Apply D Jones solved for on primary
cal.setsolve(type='G', t=60.0, table='cal.G',append=T) # Solve for G Jones in 60 sec intervals; append output
cal.solve()                                            # Do the actual solution
cal.plotcal(tablename='cal.G',plottype='PHASE',fields=2);  # Plot the calibration solution obtained

Generally you should use the above scheme, but if you want or need to (e.g. if you used 0823-500 as your primary calibrator), you can solve for D (and/or B) using the secondary instead of the primary, and just use the latter for the absolute fluxscale. If you want to solve for D using the secondary the process would look like this:

cal := calibrater('atca.ms')                    # Create a calibrater tool
cal.setdata(msselect='FIELD_ID==1')             # Select the primary calibrator (in this case id=1)
cal.setapply(type='P', t=10.0);                 # Correct for parallactic angle with 10 sec sampling.
cal.setsolve(type='G', t=30.0, table='cal.G')   # Solve for G Jones in 30 sec intervals
cal.setsolve(type='B', t=1.e6, table='cal.B')   # Solve for B Jones with an interval larger than your observation
cal.solve();                                    # Do the actual solution
cal.done()                                      # Destroy the calibrater tool

Now solve for the G Jones and D Jones terms using the secondary calibrator, e.g.:

cal := calibrater('atca.ms')                           # Create a new calibrater tool
cal.setdata(msselect='FIELD_ID==2')                    # Select the secondary calibrator (in this case id=2)
cal.setapply(type='P', t=10.0)                         # Correct for parallactic angle with 10 sec sampling.
cal.setapply(type='B', table='cal.B')                  # Apply B Jones solved for on primary
cal.setsolve(type='G', t=60.0, table='cal.G',append=T) # Solve for G Jones in 60 sec intervals; append output
cal.setsolve(type='D', t=1.e6, table='cal.D')          # Solve for D Jones using secondary
cal.solve()                                            # Do the actual solution
cal.plotcal(tablename='cal.G',plottype='PHASE',fields=2);  # Plot the calibration solution obtained

Note that the G Jones term, although designated as electronic gain, will include an atmospheric contribution, as solved for here. If separable, atmospheric corrections (e.g., WVR corrections) can be separately set or solved for as T Jones. The inclusion of a parallactic angle correction P Jones is required for all ATCA reduction, see the following section.

Next: Correcting the gains for polarization of the calibrators Up: Basic Calibration Fundamentals Previous: Setting the calibration source model Contents