Spectral-line case (only)

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Spectral-line case (only)

To obtain bandpass solutions for the spectral-line data set: select the data you want to find solutions for (the bandpass calibrator in FIELD_ID 1), reset the calibrator tool, set up to derive a single solution for phase and amplitude, and then solve. Write the bandpass solutions to a file called ngc5921.bcal and plot the solutions:

calS.setdata(msselect='FIELD_ID==1');     # Select bandpass calibrator 
                                          #  (1331+305 = 3C 286)
calS.reset();                             # Reset apply/solve state 
                                          #  of the calibrater tool
calS.setapply(type='G',                   # Arrange to apply G solutions
              t=0.0,                      #  from the table ngc5921.gcal
              table='ngc5921.gcal'); 
calS.setsolve(type='B',                   # Arrange to solve for a single 
              t=86400.0,                  #  bandpass solution for the 
              refant=14,                  #  entire observation. 
              table='ngc5921.bcal');
calS.state();                             # Review setapply/setsolve settings
calS.solve();                             # Solve for the bandpass solutions 
                                          #  and write them to the table 
                                          #  ngc5921.bcal located on disk. 
calS.plotcal(tablename='ngc5921.bcal',    # Inspect the solutions
             plottype='AMP',
             multiplot=F);

The state function provides the current state of the calibrator tool in a logger message:

  The following calibration components will be applied:
    G table=ngc5921.gcal t=0 select=[]
  The following calibration components will be solved for:
    B table=ngc5921.bcal t=86400 preavg=0 phaseonly=F refant=14 append=F

While the calibrater.solve function is running, the logger will report the status of the convergence:

  Initializing solvable bandpass terms (B-matrix)
  For interval of 86400 seconds, found 1 slots
  Applying G table from ngc5921.gcal
  Solving for B
  B Jones Slot=1, 1331+30500002, spw=1: 13-Apr-1995/09:19:00 to 13-Apr-1995/09:24:30
  B Jones    Initial fit per unit weight = 0.398437 Jy, sum of weights = 3.99722e+08
  B Jones    Final   fit per unit weight = 0.0425429 Jy after 6 iterations
  Storing B matrix in table ngc5921.bcal

As with the gain calibration, good solutions have a final fit per unit weight that is low relative to the initial fit per unit weight, as shown above. Plot the solutions graphically using the calibrater.plotcal function (Fig. 1.13):
calS.plotcal: PLOTTYPE=AMP TABLENAME=ngc5921.bcal, MULTIPLOT=False $\rightarrow$ Go
If you want solutions plotted for each antenna separately, choose MULTIPLOT=True.

$\begin{figure} % latex2html id marker 1026 \epsfig{file=cookbook.dir/vla.plotcal... ...tions for the spectral-line data set for all antennas.} \hrulefill \end{figure}$

Next: Transfer the flux density scale Up: Bandpass calibration Previous: Bandpass calibration Contents