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mfboot

Section: User Commands (1)
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NAME

mfboot - Set the flux scale of a visibility dataset.  

PERSON RESPONSIBLE

rjs  

CATEGORIES

calibration  

DESCRIPTION

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.  

PARAMETERS

vis
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.
line
Normal uv data "line" parameter, with the normal defaults. See the help on "line" for more information.
select
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.
flux
Three numbers, giving the source flux density, a reference frequency (in GHz) and the source spectral index. 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.

mode
MFBOOT can process the data in one of three modes: "triple", "scalar" and "vector". The default is "triple" for point sources and "scalar" for planets.

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 be used.

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.

clip
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).
device
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.
options
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
         the band


 

Index

NAME
PERSON RESPONSIBLE
CATEGORIES
DESCRIPTION
PARAMETERS

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Time: 18:35:38 GMT, July 05, 2011