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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):
- 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.
- Currently there is no facility for patterns of observing, such as mosaicing, since it is easy to do this via sequences of calls of observe.
- 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.
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|
|setknownconfig||Set 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|
|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|
simulator.open - Function
simulator.openfromms - Function
simulator.close - Function
simulator.done - Function
simulator.name - 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
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