hifa_wvrgcal

hifa_wvrgcal(vis=None, caltable=None, offsetstable=None, hm_toffset=None, toffset=None, segsource=None, sourceflag=None, hm_tie=None, tie=None, nsol=None, disperse=None, wvrflag=None, hm_smooth=None, smooth=None, scale=None, maxdistm=None, minnumants=None, mingoodfrac=None, refant=None, qa_intent=None, qa_bandpass_intent=None, qa_spw=None, accept_threshold=None) → ResultsList[Results][source]

Generate a gain table based on Water Vapor Radiometer (WVR) data.

Generate a gain table based on the Water Vapor Radiometer data in each vis file. By applying the wvr calibration to the data specified by qa_intent and qa_spw, calculate a QA score to indicate its effect on interferometric data; a score > 1 implies that the phase noise is improved, a score < 1 implies that it is made worse. If the score is less than accept_threshold then the wvr gain table is not accepted into the context for subsequent use.

Parameters:

  • vis --

    List of input visibility files. Default: None, in which case the vis files to be used will be read from the context.

    Example: vis=['ngc5921.ms']

  • caltable --

    List of output gain calibration tables. Default: none, in which case the names of the caltables will be generated automatically.

    Example: caltable='ngc5921.wvr'

  • offsetstable --

    List of input temperature offsets table files to subtract from WVR measurements before calculating phase corrections. Default: none, in which case no offsets are applied.

    Example: offsetstable=['ngc5921.cloud_offsets']

  • hm_toffset -- If 'manual', set the toffset parameter to the user-specified value. If 'automatic', set the toffset parameter according to the date of the MeasurementSet; toffset=-1 if before 2013-01-21T00:00:00 toffset=0 otherwise.

  • toffset -- Time offset (sec) between interferometric and WVR data.

  • segsource -- If True calculate new atmospheric phase correction coefficients for each source, subject to the constraints of the tie parameter. 'segsource' is forced to be True if the tie parameter is set to a non-empty value by the user or by the automatic heuristic.

  • sourceflag --

    Flag the WVR data for these source(s) as bad and do not produce corrections for it. Requires segsource = True.

    Example: ['3C273']

  • hm_tie -- If 'manual', set the tie parameter to the user-specified value. If 'automatic', set the tie parameter to include with the target all calibrators that are within 15 degrees of it: if no calibrators are that close then tie is left empty.

  • tie --

    Use the same atmospheric phase correction coefficients when calculating the WVR correction for all sources in the tie. If tie is not empty then segsource is forced to be True. Ignored unless hm_tie = 'manual'.

    Example: tie=['3C273,NGC253', 'IC433,3C279']

  • nsol -- Number of solutions for phase correction coefficients during this observation, evenly distributed in time throughout the observation. It is used only if segsource = False because if segsource = True then the coefficients are recomputed whenever the telescope moves to a new source (within the limits imposed by tie).

  • disperse -- Apply correction for dispersion. (Deprecated; will be removed)

  • wvrflag --

    Flag the WVR data for the listed antennas as bad and replace their data with values interpolated from the 3 nearest antennas with unflagged data.

    Example: ['DV03','DA05','PM02']

  • hm_smooth -- If 'manual' set the smooth parameter to the user-specified value. If 'automatic', run the wvrgcal task with the range of smooth parameters required to match the integration time of the wvr data to that of the interferometric data in each spectral window.

  • smooth -- Smooth WVR data on this timescale before calculating the correction. Ignored unless hm_smooth='manual'.

  • scale -- Scale the entire phase correction by this factor.

  • maxdistm --

    Maximum distance in meters of an antenna used for interpolation from a flagged antenna. Default: -1 (automatically set to 100m if >50% of antennas are 7m antennas without WVR and otherwise set to 500m).

    Example: maxdistm=550

  • minnumants --

    Minimum number of nearby antennas (up to 3) used for interpolation from a flagged antenna.

    Example: minnumants=3

  • mingoodfrac -- Minimum fraction of good data per antenna.

  • refant --

    Ranked comma delimited list of reference antennas.

    Example: refant='DV01,DV02'

  • qa_intent --

    The list of data intents on which the wvr correction is to be tried as a means of estimating its effectiveness. A QA 'view' will be calculated for each specified intent, in each spectral window in each vis file. Each QA 'view' will consist of a pair of 2-d images with dimensions ['ANTENNA', 'TIME'], one showing the data phase-noise before the wvr application, the second showing the phase noise after (both 'before' and 'after' images have a bandpass calibration applied as well). An overall QA score is calculated for each vis file, by dividing the 'before' images by the 'after' and taking the median of the result. An overall score of 1 would correspond to no change in the phase noise, a score > 1 implies an improvement. If the overall score for a vis file is less than the value in 'accept_threshold' then the wvr calibration file is not made available for merging into the context for use in the subsequent reduction. If you do not want any QA calculations then set qa_intent=''.

    Example: qa_intent='PHASE'

  • qa_bandpass_intent -- The data intent to use for the bandpass calibration in the qa calculation. The default is blank to allow the underlying bandpass task to select a sensible intent if the dataset lacks BANDPASS data.

  • qa_spw -- The SpW(s) to use for the qa calculation, in the order that they should be tried. Input as a comma-separated list. The default is blank, in which case the task will try SpWs in order of decreasing median sky opacity.

  • accept_threshold -- The phase-rms improvement ratio (rms without wvr / rms with wvr) above which the wrvg file will be accepted into the context for subsequent application.

Returns:

The results object for the pipeline task is returned.

Examples

  1. Compute the WVR calibration for all the MeasurementSets:

>>> hifa_wvrgcal(hm_tie='automatic')