This task simulates ALMA observation including 12-m, ACA 7-m and total power arrays, and images and analyzes simulated data.

This task makes multiple calls to simobserve (to calculate visibilities and total power spectra), followed by gridding of total power spectra (if total power is requested), concatenation of the simulated visibilities, calls to the simanalyze task for visibility inversion and deconvolution and calculation of difference and fidelity images, and feathering of single dish and interferometric data.

These steps may not all be familiar to new users, so the simalma task runs by default in a "dryrun" mode, in which it assesses the user's input parameters and sky model, and prints an informational report including the required calls to other CASA tasks, both to the screen and to a text file in the project directory (defined below).

The user can modify their parameters based on the information, then either run with dryrun=False to actually call the other tasks to create the simulated data, or run the other tasks individually one at a time to better understand and control the process.

NOTE: The ALMA project is refining the optimal method of combining the three types of data. If that best practice is changed after this release of CASA, the user can control the process by modifying the calls to the other CASA tasks.



project parameter

root filename for all output files.  A subdirectory will be
created, and all created files will be placed in that subdirectory
including the informational report.


skymodel parameter

input image (used as a model of the sky)
* simalma requires a CASA or fits image. If you merely have a grid of
numbers, you will need to write them out as fits or write a
CASA script to read them in and use the ia tool to create an image
and insert the data.
* simalma does NOT require a coordinate system in the header. If the
coordinate information is incomplete, missing, or you would like to
override it, set the appropriate "in" parameters. NOTE that setting
those parameters simply changes the header values, ignoring
any values already in the image. No regridding is performed.
* If you have a proper Coordinate System, simalma will do its best to
generate visibilities from that, and then create a synthesis image
according to the specified user parameters.
* You can manipulate an image header manually with the "imhead" task.

inbright parameter

peak brightness to scale the image to in Jy/pixel,
or "" for unchanged

       * NOTE: "unchanged" will take the numerical values in your image
         and assume they are in Jy/pixel, even if it says some other unit
         in the header.   

indirection parameter

central direction to place the sky model image,
or "" to use whatever is in the image already 

incell parameter

spatial pixel size to scale the skymodel image,
or "" to use whatever is in the image already.

incenter parameter

frequency to use for the center channel (or only channel,
if the skymodel is 2D)  e.g. "89GHz",
or "" to use what is in the header.

inwidth parameter

width of channels to use, or "" to use what is in the image
should be a string representing a quantity with units e.g. "10MHz"

* NOTE: only works reliably with frequencies, not velocities
* NOTE: it is not possible to change the number of spectral planes
of the sky model, only to relabel them with different frequencies
That kind of regridding can be accomplished with the CASA toolkit.

complist parameter

component list model of the sky, added to or instead of skymodel

compwidth parameter

bandwidth of components; if simulating from components only,
this defines the bandwidth of the MS and output images

setpointings parameter

if true, calculate a map of pointings and write ptgfile.
* if graphics are on, display the pointings shown on the model image
* observations with the ALMA 12m and ACA 7m arrays will observe a
region of size "mapsize" using the same hexagonal algorithm as
the ALMA OT, with Nyquist sampling.
* The total power array maps a slightly (+1 primary beam) larger area
than the 12m array does, to improve later image combination.
It samples the region with lattice grids of spacing 0.33 lambda/D.
* if setpointings=false, read pointings from ptgfile.  

ptgfile parameter

a text file specifying directions in the same
format as the example, and optional integration times, e.g.
#Epoch     RA          DEC      TIME(optional)
J2000 23h59m28.10 -019d52m12.35 10.0
* if the time column is not present in the file, it will use
"integration" for all pointings.

         * NOTE: at this time the file should contain only science pointings:
         simalma will observe these until totaltime is used up. 

integration parameter

Time interval for each integration e.g '10s'

       * NOTE: to simulate a "scan" longer than one integration, use
         setpointings to generate a pointing file, and then edit the
         file to increase the time at each point to be larger than
         the parameter integration time. 

direction parameter

mosaic center direction e.g 'J2000 19h00m00 -40d00m00'
if unset, will use the center of the skymodel image.
* can optionally be a list of pointings, otherwise
* simobserve will cover a region of size mapsize according to maptype  

mapsize parameter

angular size of mosaic map to simulate.
* set to "" to cover the model image

antennalist parameter

vector of ascii files containing antenna positions,
one for each configuration of 7m or 12m dishes.
* NOTE: In this task, it should be an ALMA configuration.
* standard arrays are found in your CASA data repository,
* a string of the form "alma;0.5arcsec" will be parsed into a
12m ALMA configuration - see
* examples: ['alma.cycle2.5.cfg','aca.cycle2.i.cfg']


hourangle parameter

hour angle of observation e.g. '-3h'
* note that if you don't add a unit, it will assume seconds.


totaltime parameter

total time of observations. This should either be a scalar
time quantity expressed as a string e.g. '1h', '3600sec', '10min',
or a vector of such quantities, corresponding to the elements of
the antennalist vector, e.g. ['5min','20min','3h'].  If you
specify a scalar, that will be used for the highest resolution
12m configuration in antennalist, and any lower resolution 12m
configurations, any 7m configurations, and any TP configurations
will have observing times relative to totaltime of 0.5, 2,and 4,


tpnant parameter

the number of total power antennas to use in simulation.


tptime parameter

if tpnant>0, the user must specify the observing time for
total power as a CASA quantity e.g. '4h'.  

       * NOTE: this is not broken up among multiple days -
         a 20h track will include observations below the horizon,
         which is probably not what is desired.

pwv parameter

precipitable water vapor if constructing an atmospheric model.
Set 0 for noise-free simulation. When pwv>0, thermal noise is
applied to the simulated data.
* J. Pardo's ATM library will be used to construct anatmospheric
profile for the ALMA site:
altitude 5000m, ground pressure 650mbar, relhum=20%,
a water layer of pwv at altitude of 2km,
the sky brightness temperature returned by ATM, and internally
tabulated receiver temperatures.
See the documentation of simobserve for more details.  

image parameter

option to invert and deconvolve the simulated MeasurementSet(s)
* NOTE: interactive clean or more parameters than the subset visible
here are available by simply running the clean task directly.
* if graphics turned on, display the clean image and residual image
* uses Cotton-Schwab clean for single fields and Mosaic gridding
for multiple fields (with Clark PSF calculation in minor cycles).


imsize parameter

image size in spatial pixels (x,y)
0 or -1 will use the model image size; example: imsize=[500,500]


imdirection parameter

phase center for synthesized image.  default is to
center on the sky model.


cell parameter

cell size e.g '10arcsec'.  "" defaults to the skymodel cell


niter parameter

number of clean/deconvolution iterations, 0 for no cleaning


threshold parameter

flux level to stop cleaning


graphics parameter

view plots on the screen, saved to file, both, or neither
verbose -- print extra information to the logger and terminal
overwrite -- overwrite existing files in the project subdirectory
please see the documents of simobserve and simanalyze for
the list of outputs produced.