pipeline.hifa.cli.hifa_wvrgcal

pipeline.hifa.cli.hifa_wvrgcal = <pipeline.hifa.cli.hifa_wvrgcal._hifa_wvrgcal object>

hifa_wvrgcal —- Generate a gain table based on Water Vapor Radiometer data, and calculate a QA score based on its effect on the interferometric 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.

——— parameter descriptions ———————————————

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: [‘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. 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.

pipelinemode dryrun acceptresults

——— examples ———————————————————–

Example

1. Compute the WVR calibration for all the MeasurementSets:

hifa_wvrgcal(hm_tie=’automatic’)