Description

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 text file (for an example of the format, see directory data/ephemerides/JPL-Horizons/).

Alternatively, for most sources, the ephemeris file can also be provided as mime format file, i.e., a saved email as obtained via the following commands:

import recipes.ephemerides.request as jplreq
jplreq.request_from_JPL(objnam='Mars', startdate='2012-01-01', enddate='2013-12-31', date_incr='0.1 d', get_axis_orientation=False,  get_axis_ang_orientation=True, get_sub_long=True, use_apparent=False, get_sep=False, return_address='YOUR_EMAIL_ADDESS',  mailserver='YOUR_MAIL_SERVER_ADDRESS')

NOTE: Some mail clients may not save the JPL mail properly. Confirmed to work in Thunderbird.

In cases where the source is not included in recipes.ephemerides.request, use the following set of commands to get the file in mime format for all sources:

  • go to the JPL ephemerides webpage 
  • change the target body entry to the desired object
  • click on 'batch-file' data in the special options section
  • retrieve the command parameter, which is the 'code' for the object (i.e., DES=C/2011 L4')
  • send an email to horizons@ssd.jpl.nasa.gov, with JOB as subject, and in the body:

!$$SOF

COMMAND= 'DES=C/2011 L4'

CENTER= '500@399'

MAKE_EPHEM= 'YES'

TABLE_TYPE= 'OBSERVER'

START_TIME= '2014-06-28'

STOP_TIME= '2014-07-01'

STEP_SIZE= '1 m'

CAL_FORMAT= 'CAL'

TIME_DIGITS= 'MINUTES'

ANG_FORMAT= 'DEG'

OUT_UNITS= 'KM-S'

RANGE_UNITS= 'AU'

APPARENT= 'AIRLESS'

SOLAR_ELONG= '0,180'

SUPPRESS_RANGE_RATE= 'NO'

SKIP_DAYLT= 'NO'

EXTRA_PREC= 'NO'

R_T_S_ONLY= 'NO'

REF_SYSTEM= 'J2000'

CSV_FORMAT= 'NO'

OBJ_DATA= 'YES'

EMAIL_ADDR = 'amoullet@nrao.edu'

QUANTITIES= '1,17,19,20,24,14,15'

!$$EOF

where COMMAND, START_TIME, STOP_TIME, STEP_SIZE and EMAIL_ADDR must be adapted to the case. See the Examples tab for how to use the returned ephemeris. 

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).