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1 Language
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  SIMULATE_\ Language summary

.nf
ADD__NOISE       : Add a random realization of noise
ARRAY           : Define the Telescope name
UV__TRACKS       : Define the UV coverage
.fi

The SIMULATE_\ Language contains commands use to simulate realistic
observations using input model sky brightness distributions.

.! ====================================================================
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1 ADD__NOISE
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  [SIMULATE_\]ADD__NOISE Noise [Bandwidth [Wcol]] [/FILES Input Output]

Add noise to the (initially noise free) simulated UV table. 
The Noise parameter indicates the expected point-source sensitivity
(in Jy) for the specified Bandwidth (in MHz). The channel spacing
of the data is used as bandwidth if argument Bandwidth is 0 or unspecified.
The default weight column is guessed by 
the command, but may be specified as 3rd argument if needed.


The noise is spread over visibilities according to the initial
weight distribution. 

Unless the /FILES option is present, the input UV data is
the UV__MODEL one created by command MODEL, and the output UV data
becomes the new UV__DATA, so that imaging can immediately proceed
with UV__MAP. 

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2 /FILES 
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  [SIMULATE_\]ADD__NOISE Noise [BandWidth [Wcol]] /FILES Input Output

Add thermal noise corresponding to the specified value Noise, for the
specified BandWidth (default: UV table spectral resolution). 

Input is the input UV table file name.

Output is the output UV table file name. It is overwritten if it 
already exists.

.! ====================================================================
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1 ARRAY
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  [SIMULATE_\]ARRAY Name
  
Specify which telescope (array) is used for the simulation.
The telescope defines the aperture sizes, the station coordinates,
the configuration possibilities and the available frequency range.

Known arrays include ACA, ALMA, NOEMA, SMA and VLA.

.! ====================================================================
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1 UV__TRACKS
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  [SIMULATE_\]UV__TRACKS Config [ ] [/FRAME [Size]] [/HORIZON MinEl] 
  [/HOUR__ANGLE Hmin Hmax] [/INTEGRATION Time] [/OFFSET Delay]
  [/SIZE Diameter] [/STATIONS List] [/TABLE [File [NEW]]] [/WEIGHT Mode]
  
  Simulate a UV coverage for the selected Configuration (or Station list)
of the current Telescope Array. Source declination is considered, and shadowing
accounted for.

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2 /FRAME
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  [SIMULATE_\]UV__TRACKS Config [ ] /FRAME [Size] [/HORIZON MinEl]
  [/HOUR__ANGLE Hmin Hmax] [/INTEGRATION Time] [/OFFSET Delay]
  [/SIZE Diameter] [/STATIONS List] [/TABLE [File [NEW]]] [/WEIGHT Mode]

  Indicate to plot the simulated UV coverage up to the specified Size
  (the default size depends on Telescope and Configuration).
  
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2 /HORIZON
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  [SIMULATE_\]UV__TRACKS Config [ ] /HORIZON MinEl [/FRAME [Size]]
  [/HOUR__ANGLE Hmin Hmax] [/INTEGRATION Time] [/OFFSET Delay]
  [/SIZE Diameter] [/STATIONS List] [/TABLE [File [NEW]]] [/WEIGHT Mode]

  Truncate the UV coverage at the specified lowest elevation (in Degree)
  
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2 /HOUR__ANGLE
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  [SIMULATE_\]UV__TRACKS Config [ ] /HOUR__ANGLE Hmin Hmax
  [/FRAME [Size]] [/HORIZON MinEl]  [/INTEGRATION Time] [/OFFSET Delay]
  [/SIZE Diameter] [/STATIONS List] [/TABLE [File [NEW]]] [/WEIGHT Mode]
  
  Truncate the UV coverage to the specified Hour angle range (in Hours)
  
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2 /INTEGRATION
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  [SIMULATE_\]UV__TRACKS Config [ ] /INTEGRATION Time
  [/FRAME [Size]] [/HORIZON MinEl] [/HOUR__ANGLE Hmin Hmax] [/OFFSET Delay]
  [/SIZE Diameter] [/STATIONS List] [/TABLE [File [NEW]]] [/WEIGHT Mode]
  
  Specify the "integration" time step in Minutes. A UV point is added for
each time step and each valid (no shadowed antenna) baseline.
  
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2 /OFFSET
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  [SIMULATE_\]UV__TRACKS Config [ ] /OFFSET Delay
  [/FRAME [Size]] [/HORIZON MinEl] [/HOUR__ANGLE Hmin Hmax]
  [/INTEGRATION Time] [/SIZE Diameter] [/STATIONS List]
  [/TABLE [File [NEW]]] [/WEIGHT Mode]

  Some arrays have a limited delay range. The /OFFSET option is meant 
to deal with the limitations of interferometers using fixed delay lines. 
The value should be entered in m.  It does not apply to radio 
interferometers (although some have limited delay ranges...) and 
the meaning of Delay is obscure...
 
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2 /SIZE 
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  [SIMULATE_\]UV__TRACKS Config [ ] /SIZE Diameter
  [/FRAME [Size]] [/HORIZON MinEl] [/HOUR__ANGLE Hmin Hmax]
  [/INTEGRATION Time] [/OFFSET Delay] [/STATIONS List]
  [/TABLE [File [NEW]]] [/WEIGHT Mode]
  
  Specify the aperture size (Diameter in m). The default size is taken
from the Telescope name given by the ARRAY command when this
Telescope is recognized.

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2 /STATIONS
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  [SIMULATE_\]UV__TRACKS Config [ ] /STATIONS List
  [/FRAME [Size]] [/HORIZON MinEl] [/HOUR__ANGLE Hmin Hmax]
  [/INTEGRATION Time] [/OFFSET Delay] [/SIZE Diameter]
  [/TABLE [File [NEW]]] [/WEIGHT Mode]

  Specify the list of stations used among those in the indicated Configuration.
By default, all stations are used.

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2 /TABLE 
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  [SIMULATE_\]UV__TRACKS Config [ ] /TABLE [File [NEW]]
  [/FRAME [Size]] [/HORIZON MinEl] [/HOUR__ANGLE Hmin Hmax]
  [/INTEGRATION Time] [/OFFSET Delay] [/SIZE Diameter]
  [/STATIONS List] [/WEIGHT Mode]
  
  Store the computed UV coverage in an output UV table for further use.
If argument NEW is present, a new file is created. Otherwise, the
coverage is appended to the pre-existing File (default: last one 
created in the current IMAGER session).

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2 /WEIGHT
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  [SIMULATE_\]UV__TRACKS Config [ ] /WEIGHT Mode [Values]
  [/FRAME [Size]] [/HORIZON MinEl] [/HOUR__ANGLE Hmin Hmax]
  [/INTEGRATION Time] [/OFFSET Delay] [/SIZE Diameter]
  [/STATIONS List] [/TABLE [File [NEW]]]

  Specify which method is used to derive the relative weights of the
visibilities as a function of Elevation. Mode can be
.nf
  UNIFORM   Each data point has the same weight
  AIRMASS   Weights are Airmass weighted, proportional to sin^2(Elevation)
or
  FULL AntGain Bandwidth [Opacity]
.fi
to use a standard noise equation based on Antenna gain, Opacity, system
temperature and observing bandwdith. AntGain is the Jy per K conversion factor
of the antennas, and Bandwidth the observation bandwidth in MHz.
Opacity is the Zenith opacity (default at start is 0.05, the value is sticky).
An empirical zenith Tsys is used, equal to 0.5 K times the observing frequency in GHz.

  The absolute weight can then be rescaled with a better effective noise estimate
and different bandwidth using the command ADD__NOISE that also implements a
proper noise generation on each visibility.

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1 ENDOFHELP
