fixplanets

fixplanets(vis, field='""', fixuvw=False, direction='', refant='0', reftime='first')[source]

Changes FIELD and SOURCE table entries based on user-provided direction or POINTING table, optionally fixes the UVW coordinates

[Description] [Examples] [Development] [Details]

Parameters

vis (path) - Name of input visibility file
field (variant=’””’) - Select field using field id(s) or field name(s)
fixuvw (bool=False) - Recalculate Fourier-plane u,v,w coordinates
direction (variant=’’) - If set, do not use pointing table but set direction to this value
refant (variant=’0’) - Reference antenna name(s)
reftime (string=’first’) - If using pointing table information, use it from this timestamp

Description

Warning

There are Known Issues for fixplanets.

The main purpose of this task is to correct observations which were performed with correct pointing and correlation but for which incorrect direction information was entered in the FIELD and SOURCE table of the MS. This may be the case if the data is old and there is no ephemeris table attached to the MS (in which case, use fixplanets with the parameter direction set in order to attach one), if improved ephemerides have become available, or if a fixed direction is needed to allow concatenation (using fixplanets as an alternative to concat).

If you actually want to change the phase center of the visibilties in an MS, you should use task fixvis.

Parameter descriptions

vis

Name of the input visibility set.

field

Field selection string.

fixuvw

Recalculates the uvw coordinates (default: False).

direction

If set, fixplanets doesn’t use the pointing table but sets the direction to this value.

default= ‘’ (use pointing table); example: ‘J2000 19h30m00 -40d00m00’.

The direction can either be given explicitly or as the path to a JPL Horizons ephemeris table, which is generated by running getephemtable.

refant

If using pointing table information, use it from this antenna. default: 0 (antenna id 0); examples: ‘DV06’ (antenna with name DV06); 3 (antenna id 3).

reftime

If using pointing table information, use it from this timestamp. default: ‘first’; examples: ‘median’ will use the median timestamp for the given field using only the unflagged maintable rows; ‘2012/07/11/08:41:32’ will use the given timestamp (must be within the observaton time).

Examples

To look up the pointing direction from antenna 0 for field ‘Titan’ in the POINTING table based on the first timestamp in the main table rows for this field, write this direction in the FIELD and SOURCE tables, and then recalculate the UVW coordinates for this field:

fixplanets(vis='uid___A002_X1c6e54_X223.ms', field='Titan', fixuvw=True)

To attach the ephemeris table ‘Titan_55438-56292dUTC.tab’ to field ‘Titan’ and then recalculate the UVW coordinates for this field:

fixplanets(vis='uid___A002_X1c6e54_X223.ms', field='Titan',
           fixuvw=True, direction='Titan_55438-56292dUTC.tab')

To set the directions for field ‘Titan’ in the FIELD and SOURCE table to the given direction and not recalculate the UVW coordinates; this can be useful for several purposes, among them preparing a concatenation of datasets. (Only fields with the same direction will be recognised as identical.):

fixplanets(vis='uid___A002_X1c6e54_X223.ms', field='Titan',
           fixuvw=False, direction='J2000 12h30m15 -02d12m00')

Development: No additional development details

Parameter Details: Detailed descriptions of each function parameter

vis (path) - Name of input visibility file

Default: none

Example: vis=’ngc5921.ms’

field (variant='""') - 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

fixuvw (bool=False) - Recalculate Fourier-plane u,v,w coordinates?

Default: False

Options: False|True

direction (variant='') - If set, do not use pointing table but set direction to

this value

Default: ‘’ (use pointing table)
Example: ‘J2000 19h30m00 -40d00m00’
The direction can either be given explicitly or
as the path to a JPL Horizons
ephemeris. Alternatively, the ephemeris table can
also be provided using getephemtable task. For more
information, see the task pages of fixplanets in
the CASA Docs.

refant (variant='0') - Reference antenna name(s); a prioritized list may be

specified

Default: 0 (antenna ID 0)

Examples: 
refant=’4’ (antenna with index 4)
refant=’VA04’ (VLA antenna #4)
refant=’EA02,EA23,EA13’ (EVLA antenna EA02,
use EA23 and EA13 as alternates if/when EA02
drops out)

Use taskname=listobs for antenna listing

reftime (string='first') - If using pointing table information, use it from this

timestamp

Default: ‘first’

Examples:

* ‘median’ will use the median timestamp for

the given field using only the unflagged

maintable rows

* ‘2012/07/11/08:41:32’ will use the given

timestamp (must be within the observaton

time)