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2.4.1 simulator - Tool

Tool for simulation



simulator provides a unified interface for simulation of telescope processing. It can create a MeasurementSet from scratch or read in an existing MeasurementSet, it can predict synthesis data onto the (u,v) coordinates or single dish data onto (ra,dec) points, and it can corrupt this data through Gaussian errors or through specific errors residing in (anti-) calibration tables. In the observing phase, simulator tries to act like a (simple) telescope. You first make a simulator tool, with the name of the MeasurementSet that you wish to construct. Next you use the various set* methods to set up the observing (sources, spectral windows, etc.). Each such setup should be given a unique name that will be used in the next step. Then you call the observe method for each observing scan you wish to make. Here you specify the source name, spectral windoow name, and observing times. After this, you have a MeasurementSet that is complete but empty. In the next phase, you fill the MeasurementSet with data from a model and then corrupt the measurements (if desired). To fill it in with a model, use the predict method. NOTE: sm.predict assumes the model image units are Jy/pixel, and in fact will overwrite the brightness units of the image itself! Finally, to apply errors, first set up the various effects using the relevant set* methods, and then call corrupt.

Some important points (mostly for the cognoscenti):

simulator changes some columns to the MeasurementSet to store results of processing. The following columns in the MS are particularly important:

The original observed visibilities are in a column called DATA. These are normally not altered by any processing in CASA. However, this simulation program does overwrite these values.
During a calibration process, as carried out by e.g. calibrater, the visibilities may be corrected for calibration effects. This corrected visibilities are stored in a column CORRECTED_DATA which is created on demand.
During various phases of processing, the visibilities as predicted from some model are required. These model visibilities are stored in a column MODEL_DATA. The ft function of the imager tool should be used to calculate the model visibility for a model image or componentmodels.

Standard tools such as the table module and the ms can be used to access and possibly change these (and all other) columns.

simulator is a tool that performs simulation of synthesis data, including (optionally) creation of a MeasurementSet, prediction of model data, and corruption by various physical effects.


simulator Construct a simulator tool
open Construct a simulator tool and creating a new MeasurementSet
openfromms Construct a simulator tool using an already existing MS
close Close the newsimulator tool
done Close the newsimulator tool
name Provide the name of the attached MeasurementSet
summary Summarize the current state
type Return the type of this tool
settimes Set integration time, etc.
observe Observe a given configuration
observemany Observe a given configuration
setlimits Set limits for observing
setauto Set autocorrelation weight
setconfig Set the antenna configuration
setknownconfigSet the antenna configuration to a known array
setfeed Set the feed parameters
setfield Set one or more observed fields
setmosaicfield Set observed mosaic fields
setspwindow Set one or more spectral windows
setdata Set the data parameters selection for subsequent processing
predict Predict astronomical data from an image
setoptions Set various processing options
setvp Set the voltage pattern model for subsequent processing
corrupt Corrupt the data with visibility errors
reset Reset the corruption terms
setbandpass Set the bandpasses
setapply Arrange for corruption by existing cal tables
setgain Set the gains
settrop Set tropospheric gain corruptions
setpointingerrorSet the Pointing error
setleakage Set the polarization leakage
oldsetnoise Set the noise level fixed sigma (mode=simplenoise) or Brown’s equation (mode=calculate) OBSOLETE VERSION
setnoise Set the noise level fixed sigma (mode=simplenoise) or Brown’s equation using the ATM model for frequency-dependent atmospheric opacity (mode=tsys-atm) or Brown’s equation, manually specifying the zenith opacity (constant across the band) and atmospheric temperature (mode=tsys-manual)
setpa Corrupt phase by the parallactic angle
setseed Set the seed for the random number generator

    simulator.simulator - Function - Function
    simulator.openfromms - Function
    simulator.close - Function
    simulator.done - Function - Function
    simulator.summary - Function
    simulator.type - Function
    simulator.settimes - Function
    simulator.observe - Function
    simulator.observemany - Function
    simulator.setlimits - Function
    simulator.setauto - Function
    simulator.setconfig - Function
    simulator.setknownconfig - Function
    simulator.setfeed - Function
    simulator.setfield - Function
    simulator.setmosaicfield - Function
    simulator.setspwindow - Function
    simulator.setdata - Function
    simulator.predict - Function
    simulator.setoptions - Function
    simulator.setvp - Function
    simulator.corrupt - Function
    simulator.reset - Function
    simulator.setbandpass - Function
    simulator.setapply - Function
    simulator.setgain - Function
    simulator.settrop - Function
    simulator.setpointingerror - Function
    simulator.setleakage - Function
    simulator.oldsetnoise - Function
    simulator.setnoise - Function
    simulator.setpa - Function
    simulator.setseed - Function

More information about CASA may be found at the CASA web page

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