Summary

Information about the observation and the performance of wvrgcal is written to the CASA logger and also returned in a dictionary; see the Water Vapor Radiometer Gain Calibration chapter in Synthesis Calibration for a more detailed description of these parameters. The dictionary element 'success' is True if no errors occured.

Of particular note is the discrepancy statistic (Disc): high values (> a few hundred microns) may indicate some levels of cloud contamination and the effect of applying the wvrgcal correction should be checked; values > 1000 $\mu$m in all antennas have currently been found to indicate that wvrgcal correction should not be used.

 

Parameter descriptions

vis

Name of input visibility file. Default: none. Examples: vis='ngc5921.ms'

caltable

Name of output gain calibration table. Default: none. Examples: caltable='ngc5921.wvr'

toffset

Time offset (sec) between interferometric and WVR data. Default: 0 (ALMA default for cycle 1, for cycle 0, i.e. up to Jan 2013 it was -1)

segsource

Do a new coefficient calculation for each source. Default: True

tie

Prioritise tieing the phase of these sources as well as possible (requires segsource=True). Default: [ ]. Examples: tie=['3C273,NGC253', 'IC433,3C279']

sourceflag

Flag the WVR data for these source(s) as bad and do not produce corrections for it (requires segsource=True). Default: [ ]. Examples: sourceflag=['3C273']

nsol

Number of solutions for phase correction coefficients during this observation. By default only one set of coefficients is generated for the entire observation. If more sets are requested, then they will be evenly distributed in time throughout the observation. Values > 1 require segsource=False. Default: 1

disperse

Apply correction for dispersion. Default: False

wvrflag

Regard the WVR data for these antenna(s) as bad and use interpolated values instead. Default: [ ]. Examples: wvrflag=['DV03','DA05','PM02']

statfield

Compute the statistics (Phase RMS, Disc) on this field only. Default: '' (all)

statsource

Compute the statistics (Phase RMS, Disc) on this source only. Default: '' (all)

smooth

Smooth the calibration solution on the given timescale. Default: '' (no smoothing). Examples: smooth='3s' smooth on a timescale of 3 seconds.

scale

Scale the entire phase correction by this factor. Default: 1. (no scaling)

spw

List of the spectral window IDs for which solutions should be saved into the caltable. Default: [ ] (all spectral windows). Examples: spw=[17,19,21,23]

wvrspw

List of the spectral window IDs from which the WVR data should be taken. Default: [ ] (all WVR spectral windows). Examples: wvrspw=[0]

reversespw

Reverse the sign of the correction for the listed SPWs (only neede for early ALMA data before Cycle 0). Default: '' (none). Examples: reversespw='0~2,4'; spectral windows 0,1,2,4

cont

Estimate the continuum (e.g., due to clouds). Default: False

maxdistm

Maximum distance (m) an antenna may have to be considered for being part of the antenna set (minnumants to 3 antennas) for the interpolation of a solution for a flagged antenna. Default: 500.

minnumants

Minimum number of near antennas required for interpolation. Default: 2

mingoodfrac

If the fraction of unflagged data for an antenna is below this value (0.0 to 1.0), the antenna is flagged. Default: 0.8

usefieldtab

Derive the antenna AZ/EL values from the FIELD rather than the POINTING table. Default: False

refant

Use the WVR data from this antenna for calculating the dT/dL parameters (can give ranked list). Default: '' (use the first good or interpolatable antenna), Examples: refant='DA45' - use DA45; refant=['DA45','DV51'] - use DA45 and if that is not good, use DV51 instead.

offsetstable

Subtract the temperature offsets in this table from the WVR measurements before using them to calculate the phase corrections (experimental). Default: '' (do not apply any offsets). Examples: offsetstable='uid___A002_Xabd867_X2277.cloud_offsets' use the given table.