Documentation on invert3

Task: invert3
Purpose: Three-dimensional Jupiter imaging.
Categories: map making


Key: vis
        Input visibility data files. Several files can be given. No default.

Key: map
        Output map (image) file name. Each output file consists of a single
        polarization/Stokes parameter. If several different pols/Stokes
        images are being made, then several file names should be given. No
        default.

Key: beam
        Output beam (point-spread function) file name. The default is not
        to make a beam.

Key: imsize
        The size of the output dataset. The default is to image out to
        primary beam half power points.

Key: pltb
        Disk black-body temperature in Kelvin that will be subtracted
        off. Default is 0.

Key: cell
        Image cell size, in arcsec. If two values are given, they give
        the RA and DEC cell sizes. If only one value is given, the cells
        are made square. The default is about one third of the resolution
        of the resultant images.

Key: fwhm
        This determines a gaussian taper to apply to the visibility data.
        It specifies the FWHM of an image-domain gaussian -- tapering the
        visibility data is equivalent to convolving with this image-domain
        gaussian.

        Either one or two values can be given, in arcsec, being the FWHM in
        the RA and DEC directions. If only one value is given, the taper is
        assumed to be symmetric. The default is no taper.

        The signal-to-noise ratio will be optimised in the output image if
        this parameter is set to the FWHM of typical image features of
        interest.

        If you are more accustomed to giving this parameter in the uv plane
        (as AIPS requires), then:
          fwhm(image plane) = 182 / fwhm(uv plane)
        where the image plane fwhm is measured in arcseconds, and the uv plane
        fwhm is measured in kilowavelengths.

Key: sup
        Sidelobe suppression area, given in arcseconds. This parameter
        gives the area around a source where INVERT attempts to suppress
        sidelobes. Two values (for the RA and DEC directions respectively)
        can be given. If only one value is given, the suppression area is
        made square. The default is to suppress sidelobes in an area as
        large as the field being mapped.

        The suppression area is essentially an alternate way of specifying
        the weighting scheme being used. Suppressing sidelobes in the entire
        field corresponds to uniform weighting (so the default corresponds to
        uniform weighting). Natural weighting gives the best signal to noise
        ratio, at the expense of no sidelobe suppression. Natural weighting
        corresponds to SUP=0. Values between these extremes give a tradeoff
        between signal to noise and sidelobe suppression, and roughly
        correspond to AIPS ``super-uniform'' weighting.

Key: robust
        Brigg's visibility weighting robustness parameter. This parameter
        can be used to down-weight excessive weight being given to
        visibilities in relatively sparsely filled regions of the u-v plane.
        Most useful settings are in the range [-2,2], with values less than
        -2 corresponding to very little down-weighting, and values greater than
        +2 reducing the weighting to natural weighting. 

        Sidelobe levels and beam-shape degrade with increasing values of
        robustness, but the theoretical noise level will also decrease.

        The default is no down-weighting (robust=-infinity).

Key: line
        Standard line parameter, with the normal defaults. See the
        help on line for more information.
        More specifically, the line parameter consists of a string
        followed by up to four numbers, viz:

          linetype,nchan,start,width,step

        where ``linetype'' is one of "channel", "wide", "velocity" or
        "felocity". The default is "channel" if spectral data is present
        in the data-set. Otherwise the default is ``wide''.

Key: select
        This allows a subset of the uv data to be used in the mapping
        process. See the Users Manual for information on how to specify
        this parameter. The default is to use all data.

Key: stokes
        Standard polarisation/Stokes parameter selection. See the help
        on stokes for more information. Several polarisations can be
        given. The default is ``ii'' (i.e. Stokes-I, given the
        assumption that the source is unpolarised).

Key: options
        This gives extra processing options. Several options can be
        given (abbreviated to uniqueness), and separated by commas:
          nocal    Do not apply gains table calibration to the data.
          nopol    Do not apply polarisation leakage corrections.
          nopass   Do not apply bandpass table calibration to the data.
          double   Normally INVERT makes the beam patterns the same
                   size as the output image. This option causes the
                   beam patterns to be twice as large.
          systemp  Weight each visibility in inverse proportion to the
                   noise variance. Normally visibilities are weighted in
                   proportion to integration time. Weighting based on the
                   noise variance optimises the signal-to-noise ratio
                   (provided the measures of the system temperature are
                   reliable!).
          tfit     Determine the planet black-body temperature.
          zflip    Flip the Z axis (useful because the visualisation
                   software uses a left-handed coordinate system).
          cotag    Put bright lines along the positive X, Y and Z axes.
          redisk   Re-add the disk as a final step.

Key: niters
        Maximum number of CLEAN iterations. The default is 0.

Key: minor
        Maximum number of CLEAN iterations per minor cycle. Default is
        niters.

Key: gain
        CLEAN gain. The default is 0.1

Key: cutoff
        The CLEAN cutoff level. The default is 0.

Key: rads
        Two values, giving the radiation belt radius (in the Jovian
        equatorial plane) and height. Both are in arcsec.