Description

WARNING: This task is currently experimental.

Summary

msuvbin is a uv gridding task. It is primarily designed to be used for large volumes of data from multiple observing epochs that need to be imaged together in order to obtain a final image product for the target source or field of interest. One way of proceeding with such large multi-epoch data is to image each epoch separately and average the images afterward. Instead, msuvbin averages the visibilities on a common uv grid, then the resulting data product can be imaged using the task clean or tclean. Averaging such uv data into a common uv grid first has several conveniences and advantages, such as easily doing the proper weighted average. More details on this task can be found in the EVLA Memo 198, which explains the current implementation in msuvbin and its limitations. In particular, note the issue/limitation of creating a uv grid with wprojection and then using Cotton-Schwab major cycles to image it; see the EVLA Memo 198 for more details.

 

Parameter descriptions

vis

Name of input visibility file

field

Field name list; note that this position will define the phase center of the output uv grid

spw

Spectral window selection

taql

TaQl expression for data selection (see Data Selection in a Measurement Set or CASAcore NOTE 199: Table Query Language for more information)

outvis

Name of output grid

phasecenter

Phase center of the grid, to be used when the phase center of the selected field is not the desired output phase center. Example: phasecenter='J2000 18h03m04 -20d00m45.1'

nx

Number of pixels along the x axis of the grid. Default: 1000

ny

Number of pixels along the y axis of the grid. Default: 1000

cell

Cellsize of the grid (given in sky units). Default: '1arcsec'

ncorr

Number of correlation/polarization plane in uv grid (allowed 1, 2, 4). For example, if the input data set has the correlations RR and LL, and ncorr=1, then the output uv grid will be written as Stokes I. If ncorr=2, then the output grid will have both the RR and LL correlations. Default: 1

nchan

Number of spectral channels in the output uv grid. Default: 1

fstart

Frequency of the first channel. Default: '1GHz' (the user needs to give a useful input here)

fstep

Width of spectral channel. Default: '1kHz'

wproject

Do wprojection correction while gridding. Default: False

memfrac

Controls how much of computer's memory is available for gridding. Default=0.5