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Basic Information on mfboot
Purpose: Set the flux scale of a visibility dataset.
MFBOOT is a MIRIAD program that corrects the flux scale in
visibility datasets. In doing this, it assumes that the flux
density scale is out by a constant scale factor. MFBOOT computes
and applies a scale factor to the calibration tables of visibility
datasets to account for this.
To determine this factor, MFBOOT compares the flux
density of measured visibilities with models of the expected
visibility. The visibilities can correspond to measurements of
planets or point sources. For point sources, they can be either
standard calibrators with known flux density, or others. In the
latter case the user must specify its flux density.
Input visibility datasets. Several datasets can be given (wildcards
are supported). The scale factor will be applied uniformly to all
datasets whether or not they contain the source used to determine it.
Normal uv data line parameter, with the normal defaults. See
the help on line for more information.
Normal uv-selection parameter. This selects the data in the input
datasets to analyse. The data selected should consist of
a single planet or point source. See the help on ``select'' for more
information. For planets, you may wish to select just the shortest
spacing, where the planet is strongest.
Three to five numbers, giving the source flux density, a reference
frequency (in GHz), the source spectral index and optionally two
higher order terms. The flux and spectral index are at the reference
frequency. If no values are given, then MFBOOT checks whether the
source is one of a set of known sources or a planet, and uses
the appropriate flux variation with frequency.
MFBOOT has built-in models for a few calibrators as well as the
planets - see calplot and plplt.
For a point source, this parameter gives the flux density of the
calibrator in Janskys. For a planet, this parameter gives the
brightness temperature of the planet in Kelvin.
MFBOOT can process the data in one of three modes: "triple", "scalar"
and "vector". The default is "triple" for point sources and "scalar"
In "triple" mode, MFBOOT compares the triple product of the data
and model. The advantage of comparing triple products is that the
process is robust to phase errors, and the data do not need to be
phase calibrated. Because planets can be significantly resolved,
triple mode is often not appropriate for them. However if the
resolution is modest on the selected baselines, triple mode can
In "scalar" mode, the amplitude of the data and model are compared.
This is also robust to phase errors, but will experience a noise
bias when the signal to noise is poor. Planets are often sufficiently
strong that noise bias is not an issue.
In "vector" mode, the real part of the data is compare with the model.
The data need to be phase calibrated.
For planets, this parameter can be used to discard data for baselines
that are significantly resolved. Data for a particular baseline will
be discarded when the expected flux density on that baseline is
less than the clip factor times the total flux density. The clip
parameter takes on values between 0 to 1.0, with the default being 0
(ie the default is to accept all data).
PGPLOT device to plot the model data as well as the visibility
data. The default is to not produce a plot. No plot is produced
in triple mode.
Extra processing options. Several can be given, separated by commas.
noapply Do not apply the scale factor - just evaluate it.
nospec Do not try to determine and correct the spectral index across
Revision: 1.15, 2014/06/05 03:49:06 UTC
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