simulator - Tool

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2.4.1 simulator - Tool

Tool for simulation
Requires:

Synopsis

Description

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, an atmospheric model, or through specific errors residing in (anti-) calibration tables.

In the observing phase, simulator creates a MeasurementSet and calculates uvw values. 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 (antenna locations, sources, spectral windows, etc.). Then you call the observe method for each observing scan you wish to make, or observemany to create several scans. You specify the source name, spectral window name, and observing times. After this, you have a MeasurementSet that is complete but visibilities=0.

In the prediction phase, you fill a MeasurementSet (either one newly created or a pre-existing one, perhaps from a real telescope) with data from a model or componentlist, and then corrupt the measurements (if desired).

NOTE: sm.predict assumes model image units are Jy/pixel, and in fact will overwrite the brightness units of the image itself!

The ft function of the imager tool can also be used to calculate the model visibility for a model image or componentmodels.

To apply errors, first set up the various effects using the relevant set* methods, and then call corrupt.

Some important details: - One call to observe generates one scan (all rows have the same SCAN_NUMBER). - The start and stop times specified to observe need not be contiguous and so one can simulate antenna drive times or other gaps. - Currently there is only a rudimentary method to calculate patterns of observing (mosaicing), since it is easy to do this via sequences of calls of observe, or simutil::calcpointings, or the simobserve task - The heavy duty columns (DATA, FLAG, IMAGING_WEIGHT, etc. are tiled. New tiles are generated for each scan. Thus the TSM files will not get very large. - predict(incremental=False) calculates new visibilities and replaces the DATA column, - predict(incremental=True) calculates new visibilities, adds them to the DATA column - predict for any value of incremental then sets CORRECTED_DATA equal to DATA, and MODEL_DATA to 1

Methods

simulator	Construct a simulator tool
open	Construct a simulator tool and create a new MeasurementSet
openfromms	Construct a simulator tool using an already existing MS
close	Close the simulator tool
done	Close the simulator 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
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 or components

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
setpointingerror	Set 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

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