13.3 The ``Standard Calibration (2-receivers)'' procedure

We describe here, step by step the inputs and actions (or outputs) of the procedure ``Standard Calibration (2 receivers) ''. The associated panel is given in Fig.13.2.

Figure 13.2: ``Standard Calibration (2 receivers)'' panel

13.3.1 Inputs

On the panel, the reducer should select with the mouse the ``File name'' of the header file. Other parameters are automatically selected by the procedure if the flag ``Use previous settings'' is set to YES which is the default. Never change it if your data are correct (no editing). The parameters ``First and last scan'' are selected automatically when ``Use previous settings'' is set to YES. The default value for the flag Min.Data quality is AVERAGE. The flag ``Use Phase correction'' must also be set to the default: YES. The current procedure uses by default the phase calibration of the receiver 1 to calibrate the instrumental phase of the receiver 2 because the experience has shown that it is the most efficient way to proceed (see R.Lucas lecture on phase calibration). Therefore, the calibration of the receiver 2 (1.3mm) cannot be dissociated from the calibration of the receiver 1 (3mm) and the flag ``Receivers numbers'' must be set to 1 2, except when observations were done at 3mm only.

Finally, the inputs ``R1 Fluxes'' and ``R2 fluxes'' are associated (when needed) to the action EFF)

13.3.2 Actions or Outputs

To calibrate your data, you need to do the following actions leading to the output calibration, in order:

1. SELECT: Select the calibration parameters
2. PHCOR: Radiometric phase correction, equivalent to a ``Monitor 0'', see A.Dutrey lecture.
3. RF: Radio Frequency calibration
4. PHASE: Instrumental phase calibration versus time
5. EFF: Efficiency (Jy/K) calibration, to determine the flux densities of the amplitude calibrator. The inputs ``R1 Fluxes'' and ``R2 Fluxes'' should be used here.
6. AMP: Amplitude calibration versus time
7. PRINT: To produce the LaTeX and PostScript files containing the calibration curves (e.g.
   28-feb-2001-x007.ps).

By typing GO, all the actions listed above are done sequentially. The reducer has just to type continue under CLIC (or use the ``Continue'' button in the top left menu) at each step of the calibration process.

13.3.3 Results of the calibration

After a few general comments about quality of the data, including the measurement of the seeing (deduced from the rms of the fit of the temporal phase), the pages 1 and 2 summarize the calibration as follows:

• §1.1 The estimated flux densities of the calibrators at the observed frequencies.
• §1.2 The efficiencies of the antennas for receivers 1 and 2 (which are deduced by fixing the flux of one or several calibrators).
• §1.3 The hour angle observed on the source
• §1.4 The table of the rms obtained on the RF calibration for receivers 1 and 2 in both upper and lower sidebands
• §1.5 The table of the rms obtained the temporal fit for the phase and the amplitude per baselines. Note that for receiver 2, the rms given in Col.1 is exactly the product of frequency ratio (rece 2/rece 1) times the rms obtained on receiver 1 because the phase on the receiver 1 is used to calibrate the phase on the receiver 2. After applying this phase correction, a second fit is performed on the residuals, its rms is displayed on Col.2. Col.3 gives the rms obtained on the amplitude (in %).