fixvis – Recalculates (u, v, w) and/or changes Phase Center – editing, manipulation task

Description

Recalculates (u, v, w) and/or changes Phase Center.

If the phase center is changed, the corresponding modifications are applied to the visibility columns given by the parameter “datacolumn” which is by default set to “all” (DATA, CORRECTED, and MODEL).

Parameters

Title

Parameter	Default	Description
vis	''	Name of input visibility file
outputvis	''	Name of output visibility file
field	[ ]	Select field using field id(s) or field name(s)
refcode	''	reference frame to convert UVW coordinates to
reuse	True	base UVW calculation on the old values?
phasecenter	''	use this direction as phase center
distances	[ ]	(experimental) List of the distances (as quanta) of the fields selected by field.
datacolumn	'all'	when applying a phase center shift, modify visibilities only in this/these column(s)

Parameter Explanations

vis

''

Name of input visibility file

Default: none

Example: vis=’ngc5921.ms’

outputvis

''

Name of output visibility file

Default: ‘’ (same as vis)

Example: outputvis=’ngc5921_out.ms’

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

refcode

''

Reference frame to convert UVW coordinates to

Default: ‘’ (refcode of PHASE_DIR in the FIELD table)

Example: refcode=’B1950’

reuse

True

Base UVW calculation on the old values?

Default: True Options: True|False

Note: ignored if parameter ‘phasecenter’ is set

phasecenter

''

If set to a valid direction: change the phase center for the given field to this value

If given without the equinox, e.g. ‘0h01m00s +00d12m00s’, the parameter is interpreted as a pair of offsets in RA and DEC to the present phasecenter.

Example: phasecenter=’J2000 9h25m00s -05d12m00s’

Note: The RA offset can be given in units of time or angle. If given as a time (i.e. as a single number with a time unit as in, e.g., 12s or in the XXhXXmXXs or XX:XX:XX.XXX formats), it is applied as is. If given as an angle (e.g., 0.01deg), it is divided by the cos(DEC) before it is applied.

distances

[ ]

(experimental) List of the distances (as quanta) of the fields selected by field.

Default: [] (the distances of all fields are assumed to be infinity.)

If not a list but just a single value is given, this is applied to all fields.

Examples: distances=[‘2E6km’, ‘3E6km’] distances=’15au’

datacolumn

'all'

when applying a phase center shift, modify visibilities only in this/these column(s)

Default: ‘all’ (DATA, CORRECTED, and MODEL)

Example: datacolumn=’DATA,CORRECTED’ (will not modify MODEL)