Basic Information on uvplanet

Task: uvplanet
Purpose: Fiddle planetary and solar system data.
Categories: uv analysis

uvplanet is a Miriad task used to fiddle visibility datasets
from planetary (and other solar system) observations. It can:
  - Add planet orientation parameters (plmaj,plmin,plangle) to
    the dataset. uvplanet recognises planets by their source name,
    and knows their orientations as a function of time.
  - Apply a time-varying phase shift to track the object.
  - Subtract a thermal disk.
  - Subtract background sources, accounting for a moving phase centre.

Key: vis
The name of the input uv datasets. Several can be given
Wildcards are supported. No default.

Key: out
The name of the output uv data-set. There is no default name.

Key: select
The normal uv selection commands. The default is to select everything.

Key: pltb
Parameters for planets only, which determine model for the planetary
disk to be subtracted off. It consists of one or two values. The
first is the blackbody temperature of the disk, in Kelvin.
The second is the limb darkening parameter. The limb darkening
parameter is a value between 0 and 1. The apparent brightness of
the disk falls off as cos(theta)**limb.
uvplanet has built-in ephemerides and models of the planets which
gives their apparent sizes and shapes.
The default is 0 for both parameters (i.e. do not subtract off a disk).

Key: options
This gives extra processing options. Several options can be given,
each separated by commas. They may be abbreviated to the minimum
needed to avoid ambiguity. Possible options are:
   replace     Replace the data with the blackbody disk and point
               sources (the normal behaviour is to subtract the
               blackbody disk and point sources).
   magnetic    For Jupiter only: The magnetic axis is used to 
               set planet orientation parameters. This overrides the
               normal behaviour of using the spin axis.
   arcane      The format for the pmotion text files is the
               "arcane" format (see below).
The following options can be used to turn off calibration corrections.
The default is to apply any calibration present.
   nocal       Do not apply the gains table.
   nopass      Do not apply bandpass corrections.
   nopol       Do not apply polarization corrections.

Key: sources
This gives the position and flux of point sources to be subtracted
from the visibility dataset. Many sources can be given. Each
source is specified by three numbers:
  ra dec flux
The RA and DEC are in normal Miriad format, and the flux is in Jy.

Key: pmotion
This parameter allows phase shifts to be applied to the data to
make the phase centre track the object of interest. Assuming that
the object has significant proper motion, this can
correct for phase tracking errors (e.g. wrong ephemeris) or perhaps 
no tracking at all. One or two tracking files can be given. The first
file gives the centre of the object (as a function of time). The second
gives the phase centre of the observation (as a function of time).
If both files are given, the data are phase shifted to the centre
of the object (i.e. corrects for tracking errors). If only one file
is given, then the RA and DEC in the dataset are taken as the
phase centre of the telescope.

The "pmotion" parameter can also be used to correct the RA and DEC
stored in the dataset. If these are incorrect (e.g. many telescopes
and the FITS format, do not store the time-varying RA/DEC, even though
they track time varying RA/DEC), then giving the one text file
twice will cause the RA and DEC to be corrected and no shifts being
applied.

The text files contain potentially many lines, with each line
giving a sky position at a given time.
Two formats for the text files are possible (if there are
two input files, both must be in the same format). The normal format
consists of 3 values per line, being

  time ra dec

with "time" (UTC), "ra" and "dec" being the position of the object at
a given time. The time, ra and dec are in the normal Miriad formats.
The times should be in increasing order. Linear interpolation
is used to estimate positions between the given times.

A convenient way to develop this file is through the JPL ``Horizons''
service. This is accessed through

  telnet ssd.jpl.nasa.gov 6775

Using a text reformating tool (e.g. PERL), the output from Horizons
is readily converted to the format required by uvplanet.
Documentation on the Horizons system is available from

  http://ssd.jpl.nasa.gov/horizons.html

The other possible format is the ``arcane'' format, which will be 
expected if "options=arcane" is given. This format is provided for
obscure historical support. It consists of 6 values per line, being

  start_time time ra dec dra ddec

The times are in modifed Julian days, ra and dec are in turns,
and the rate parameters, "dra" and "ddec", are in turns/day. The
record is considered valid after "start_time", and the rates
are used to estimate positions between given times.

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