Use Case: ValidatePhaseCorrection


The Pipeline Calibration determines the validity of the phase correction deduced from the previous WVR measurements and applied directly at the correlator level on current observation, which is made on a strong point source. The data can also be used to improve the WVR correction factors (pathlength versus WVR data).

Role(s)/Actor(s):
Primary: Calibration Pipeline
Secondary: ***

Priority: ***

Performance: < second

Frequency: seconds to minutes

Preconditions:

  1. The validation of phase correction is initiated by the Calibration Pipeline either after each scan on a phase calibrator, using channel averages at sub-integration time, or several successive scans on a phase calibrator using time averages of length depending on the configuration size.
  2. Input:
    • Per baseline and subbands: Raw and phase corrected complex visibilities on phase calibrator;
    • Validation kind (i.e. subband or time average).
  • This assumes that the phase correction has been applied on calibrator complex visibilities at the correlator level.

    • Basic Course:

    1. [this step is done by the correlator, it should not be mentioned here] Depending on validation kind, compute either time or subband averages of both the raw and the corrected complex visibilities.

      2. Exception Course: Processing is stopped and returns a specific error code.
    2. Compute the amplitudes of the raw and the corrected complex visibilities.

      3. Exception Course: Processing is stopped and returns a specific error code.
    3. Set a validity flag from the comparison of the raw and corrected amplitudes (i.e. the largest the amplitude, the best result). This should take into account the uncertainties due to thermal fluctuations in each quantity.

      4. Exception Course: Processing is stopped and returns a specific error code.


    Postconditions:

    1. Output:
      • Validity flag per baseline, integration time and subband;
      • Error code.
    2. The output is fed back to the Calibration Pipeline.


    Issues to be Determined or Resolved:

    1. Is there any possible check of input data consistency?
    2. By comparing corrected and uncorrected phases it should also be possible to refine empirically the WVR correction factors (the frequency dependence of the water line fluctuations can be different from its total spectrum, because the altitude profile of the fluctuating water may differ from the toal altitude profile of water).
      This requires a particularly strong phase calibrator.

    Notes:

    1. ***

    Owner: Jerome Pety.
    Last modified by $Author: lucas $ on $Date: 2003/02/14 12:13:08 $