exportuvfits – Convert a CASA visibility data set to a UVFITS file: – import/export task

Description

This task writes a UVFITS file, a general format data set used to transfer data between different software systems. It is written in floating point format. Different programs have different restrictions on what forms of UVFITS files they will use, especially whether they will accept multiple sources and/or spectral windows in the same file. See the spw, multisource, and combinespw descriptions below.

IMPORTANT NOTE: In general, some of the data averaging features of this task have never worked properly. In general, users should run mstransform to select and average data prior to running exportuvfits. The associated input parameters are being slowly deprecated and removed.

Parameters

Title

Parameter	Default	Description
vis	''	Name of input visibility file
fitsfile	''	Name of output UV FITS file
datacolumn	'corrected'	Visibility file data column
field	''	Select field using field id(s) or field name(s)
spw	''	Select spectral window/channels
antenna	''	Select data based on antenna/baseline
timerange	''	Select data based on time range
writesyscal	False	Write GC and TY tables (not yet available)
multisource	True	Write in multi-source format?
combinespw	True	Export the spectral windows as IFs
writestation	True	Write station name instead of antenna name
padwithflags	False	Fill in missing data with flags to fit IFs
overwrite	False	Overwrite output file if it exists?

Parameter Explanations

vis

''

Name of input visibility file

Default: none

Example: vis=’ngc5921.ms’

fitsfile

''

Name of output UV FITS file

Default: none

Example: vis=’ngc5921XC1.fits’

datacolumn

'corrected'

Visibility file data column

Default: corrected Options: ‘data’(raw)|’corrected’|’model’|’weight’

Example: datacolumn=’model’

field

''

Select field using field id(s) or field name(s)

Default: ‘’ –> all fields

Use ‘go listobs’ to obtain the list id’s or names. If field string is a non-negative integer, it is assumed a field index, otherwise, it is assumed a field name.

Examples: field=’0~2’; field ids 0,1,2 field=’0,4,5~7’; field ids 0,4,5,6,7 field=’3C286,3C295’; field named 3C286 and 3C295 field = ‘3,4C*’; field id 3, all names starting with 4C

spw

''

Select spectral window/channels

Examples: spw=’0~2,4’; spectral windows 0,1,2,4 (all channels) spw=’<2’; spectral windows less than 2 (i.e. 0,1) spw=’0:5~61’; spw 0, channels 5 to 61, INCLUSIVE spw=’*:5~61’; all spw with channels 5 to 61 spw=’0,10,3:3~45’; spw 0,10 all channels, spw 3, channels 3 to 45. spw=’0~2:2~6’; spw 0,1,2 with channels 2 through 6 in each. spw=’0:0~10;15~60’; spectral window 0 with channels 0-10,15-60. (NOTE ‘;’ to separate channel selections) spw=’0:0~10^2,1:20~30^5’; spw 0, channels 0,2,4,6,8,10, spw 1, channels 20,25,30 type ‘help par.selection’ for more examples.

antenna

''

Select data based on antenna/baseline

Subparameter of selectdata=True Default: ‘’ (all)

If antenna string is a non-negative integer, it is assumed an antenna index, otherwise, it is assumed as an antenna name

Examples: antenna=’5&6’; baseline between antenna index 5 and index 6. antenna=’VA05&VA06’; baseline between VLA antenna 5 and 6. antenna=’5&6;7&8’; baselines with indices 5-6 and 7-8 antenna=’5’; all baselines with antenna index 5 antenna=’05’; all baselines with antenna number 05 (VLA old name) antenna=’5,6,10’; all baselines with antennas 5,6,10 index numbers

timerange

''

Select data based on time range

Subparameter of selectdata=True Default = ‘’ (all)

Examples: timerange = ‘YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss’ (Note: if YYYY/MM/DD is missing date defaults to first day in data set.) timerange=’09:14:0~09:54:0’ picks 40 min on first day timerange= ‘25:00:00~27:30:00’ picks 1 hr to 3 hr 30min on NEXT day timerange=’09:44:00’ pick data within one integration of time timerange=’>10:24:00’ data after this time

writesyscal

False

Write GC and TY tables. Not yet available.

Default: False

multisource

True

Write in multi-source format?

Default: True

Set to False if only one source is selected.

Note: diffmap does not work on multisource uvfits files, so if planning on using diffmap on the resulting uvfits file, select a single source and set multisource = False. Otherwise use True. (If multiple sources are selected, a multi-source file will be written no matter what the setting of this parameter).

combinespw

True

Export the spectral windows as IFs?

Default: True

If True, export the spectral windows as IFs. All spectral windows must have same shape. Otherwise multiple windows will use multiple FREQIDs.

writestation

True

Write station name instead of antenna name

Default: True

padwithflags

False

Fill in missing data with flags to fit IFs

Subparameter of combinespw=True Default: True

If True, and combinespw is True, fill in missing data as needed to fit the IF structure. This is appropriate if the MS had a few frequency-dependent flags applied, and was then time-averaged by split, or when exporting for use by difmap. If the spectral windows were observed at different times, padwithflags=True will add a large number of flags, making the output file significantly longer. It does not yet support spectral windows with different widths.

overwrite

False

Overwrite output file if it exists?

Default: False Options: False|True