#
# stub function definition file for docstring parsing
#
[docs]def simobserve(project='sim', skymodel='', inbright='', indirection='', incell='', incenter='', inwidth='', complist='', compwidth='"8GHz"', comp_nchan=1, setpointings=True, ptgfile='$project.ptg.txt', integration='10s', direction='', mapsize=['', ''], maptype='hexagonal', pointingspacing='', caldirection='', calflux='1Jy', obsmode='int', refdate='2014/01/01', hourangle='transit', totaltime='7200s', antennalist='', sdantlist='aca.tp.cfg', sdant=0, outframe='LSRK', thermalnoise='tsys-atm', user_pwv=0.5, t_ground=270., t_sky=260., tau0=0.1, seed=11111, leakage=0.0, graphics='both', verbose=False, overwrite=True):
r"""
visibility simulation task
[`Description`_] [`Examples`_] [`Development`_] [`Details`_]
Parameters
- project_ (string='sim') - Root prefix for output file names
- skymodel_ (string='') - model image to observe
.. raw:: html
<details><summary><i> skymodel != '' </i></summary>
- inbright_ (string='') - Peak brightness to scale the image to in Jy/pixel
- indirection_ (string='') - Set new direction, e.g. J2000 19h00m00 -40d00m00
- incell_ (string='') - Set new cell/pixel size, e.g. 0.1arcsec
- incenter_ (string='') - Set new frequency of center channel e.g. 89GHz (required even for 2D model)
- inwidth_ (string='') - Set new channel width, e.g. "10MHz" (required even for 2D model)
.. raw:: html
</details>
- complist_ (string='') - Componentlist to observe
.. raw:: html
<details><summary><i> complist != '' </i></summary>
- compwidth_ (string='"8GHz"') - Bandwidth of components
- comp_nchan_ (int=1) - Channelization of components
.. raw:: html
</details>
- setpointings_ (bool=True) - Calculate a map of pointings?
.. raw:: html
<details><summary><i> setpointings = True </i></summary>
- integration_ (string='10s') - Integration (sampling) time
- direction_ (stringVec='') - Mosaic center direction, e.g J2000 19h00m00 -40d00m00
- mapsize_ (stringVec=['', '']) - Angular size of mosaic map to simulate.
- maptype_ (string='hexagonal') - how to calculate the pointings for the mosaic observation: hexagonal, square (raster), ALMA, etc.
- pointingspacing_ (string='') - Spacing in between pointings e.g. 0.25PB. ALMA default: INT=lambda/D/sqrt(3), SD=lambda/D/3
.. raw:: html
</details>
.. raw:: html
<details><summary><i> setpointings = False </i></summary>
- ptgfile_ (string='$project.ptg.txt') - List of pointing positions
- integration_ (string='10s') - Integration (sampling) time
.. raw:: html
</details>
- obsmode_ (string='int') - Observation mode to simulate [int(interferometer)|sd(singledish)|(none)]
.. raw:: html
<details><summary><i> obsmode = int </i></summary>
- antennalist_ (string='') - Interferometer antenna position file
- refdate_ (string='2014/01/01') - Date of observation. Not critical unless concatting simulations
- hourangle_ (string='transit') - Hour angle of observation center, e.g. -3:00:00, 5h
- totaltime_ (string='7200s') - Total time of observation or number of repetitions
- caldirection_ (string='') - pt source calibrator [experimental]
- calflux_ (string='1Jy') - pt source calibrator flux [experimental]
.. raw:: html
</details>
.. raw:: html
<details><summary><i> obsmode = sd </i></summary>
- sdantlist_ (string='aca.tp.cfg') - Single dish antenna position file
- sdant_ (int=0) - Single dish antenna index in file
- refdate_ (string='2014/01/01') - Date of observation. Not critical unless concatting simulations
- hourangle_ (string='transit') - Hour angle of observation center, e.g. -3:00:00, 5h
- totaltime_ (string='7200s') - Total time of observation or number of repetitions
.. raw:: html
</details>
.. raw:: html
<details><summary><i> obsmode = '' </i></summary>
- antennalist_ (string='') - Interferometer antenna position file
- sdantlist_ (string='aca.tp.cfg') - Single dish antenna position file
- sdant_ (int=0) - Single dish antenna index in file
.. raw:: html
</details>
- outframe_ (string='LSRK') - Spectral frame of MS to create
- thermalnoise_ (string='tsys-atm') - add thermal noise: [tsys-atm|tsys-manual|(none)]
.. raw:: html
<details><summary><i> thermalnoise = tsys-atm </i></summary>
- user_pwv_ (double=0.5) - Precipitable Water Vapor in mm
- t_ground_ (double=270.) - Ground/spillover ambient temperature in K
- seed_ (int=11111) - Random number seed
.. raw:: html
</details>
.. raw:: html
<details><summary><i> thermalnoise = tsys-manual </i></summary>
- t_ground_ (double=270.) - Ground/spillover ambient temperature in K
- t_sky_ (double=260.) - Atmospheric temperatur in K
- tau0_ (double=0.1) - Zenith opacity
- seed_ (int=11111) - Random number seed
.. raw:: html
</details>
- leakage_ (double=0.0) - Cross polarization (interferometer only)
- graphics_ (string='both') - Display graphics at each stage to [screen|file|both|none]
- verbose_ (bool=False) - Print extra information to the logger and terminal
- overwrite_ (bool=True) - Overwrite existing files in the project subdirectory
.. _Description:
Description
.. warning:: There are `Known Issues <../../notebooks/introduction.html#Known-Issues>`__ for simobserve.
This task simulates interferometric or total power
MeasurementSets. The general steps for simulation in CASA are
described on the top
`Simulation <../../notebooks/simulation.ipynb>`__
page. We describe the first two steps in more detail here.
#. Make a model image or componentlist representation of the sky
brightness distribution.
#. Use the **simobserve** task to create a MeasurementSet (uv
data).
.. rubric:: Generating a Model Image
A "model image" is a CASA image or FITS file that contains a
representation of the sky brightness distribution, and it
represents the object to be "observed" in the simulation. There
are several ways to generate a model image.
.. rubric:: Starting from an existing FITS image
The simplest option is to begin with an existing FITS image. The
image can be either a single plane (i.e., one observed frequency
channel) or a cube. A common simulation exercise is to begin with
a FITS file representing an observation of a target, then scale
the spatial axes and the flux to shift the data to what would be
observed for a similar target at a different distance. The
**simobserve** task has parameters to set the peak flux density,
coordinates on the sky, pixel size, frequency of the center
channel, and channel width.
.. rubric:: Starting from a component list
.. warning:: **WARNING**: **simobserve** does not currently handle component
lists correctly for single-dish-only simulations. It is advised
to convert the component list to an image or FITS file.
It may be useful to simulate observations of an idealized model
image consisting, for example, of point sources and Gaussians. The
CASA component list tool (**cl**) allows the user to specify a set
of point sources, Gaussians, and disks. One
can then either use that component list directly
in **simobserve**, or create a CASA image from the components, or
both. Details can be found in `this CASA
guide <http://casaguides.nrao.edu/index.php?title=Simulation_Guide_Component_Lists_%28CASA_6.5.3%29>`__.
.. rubric:: Starting from a GIF or JPG image
A user may wish to convert a GIF or JPG image to a FITS file for
simulation in CASA. The image should be converted to a 32-bit FITS
image for use with the CASA sim tools. See `this
page <http://casaguides.nrao.edu/index.php?title=Convert_jpg_to_fits>`__
for an example of using gimp to convert a JPG image to a FITS
file. Alternatively, you could use ImageMagik from the command
line, like so:
::
convert myfile.jpg myfile.fits
Then proceed to trim and convert the file in CASA like so:
::
importfits(fitsimage='myfile.fits',imagename='testimage',overwrite=T)
default 'immath'
imagename = 'testimage'
expr = 'IM0'
box = '0,0,299,299'
outfile = 'testimage2'
immath()
You can use **imhead** to modify the header parameters of the new
image, or you can use the parameters in the **simobserve** task to
modify the peak flux density, coordinates on the sky, pixel size,
frequency of the center channel, and channel width. See the
discussion below.
.. rubric:: Generating visibilities with simobserve
The task **simobserve** takes several steps to generate observed
visibilities. The major steps are:
- Modify Model: If desired, you can modify the header parameters
in your data model to mimic different observing targets. For
example, if you start with a model of M100 you might wish to
scale the axes to simulate an observation of an M100-like
galaxy that is 4X more distant.
- Set Pointings: If the angular size of your model image is
comparable or larger than the 12-m primary beam, you can
simulate observing the target as a mosaic. In this step, the
individual pointings are determined and saved in a text file.
You can also generate such a text file yourself.
- Generate visibilities: The visibilities are determined based on
the telescope and configuration specified, and the length in
time of the observation.
- Finally, noise can be added to the visibilities. The
**simobserve** task uses the
`aatm <http://www.mrao.cam.ac.uk/%7Ebn204/alma/atmomodel.html>`__
atmospheric model (based on Juan Pardo's
`ATM <http://cab.inta-csic.es/users/jrpardo/class_atm.html>`__
library) to simulate real observing conditions. It can corrupt
the data with thermal noise and atmospheric attenuation.
Corruption with an atmospheric phase screen, or adding gain
fluctuations or drift, can be added subsequently using the
**simulator** tool **sm** as described in `this CASA
guide <https://casaguides.nrao.edu/index.php?title=Corrupting_Simulated_Data_%28Simulator_Tool%29>`__.
For details, please see the descriptions of the individual
parameters below.
.. warning:: **WARNING**: It is currently not possible to generate a MS in a
frame other than J2000 e.g., if you set *indirection* to "ICRS
19h00m00 -40d00m00" it will silently assume that to actually be
"J2000 19h00m00 -40d00m00". The reference frame can be set to
ICRS during the imaging or **simanalyze** process.
.. warning:: **WARNING**: when using a simulated MS in **tclean**, it should
be considered best practice to declare the *phasecenter*
parameter using the 'J2000 xx:xx:xx.xxx +xxx.xx.xx.xxx'
notation to account for possible rounding errors that can
create an offset in the simulated image.
.. note:: **NOTE**: **simobserve** calls **sm.predict** with
**sm.setvp** (*dovp=True*). This means that the vpmanager will
be queried, and a primary beam pattern will be applied,
according to the telescope name. One can set the primary beam
for the given telescope using the **vpmanager**. In most
circumstances, **simobserve** will use synthesis gridding
(image-plane primary beam application), unless 1) there are
more than 1 pointing, AND 2) there are more than one antenna
diameter in the configuration file. In that case it will
**sm.setoptions** (*ftmachine="mosaic"*) which enables
heterogenous array simulation for ALMA, ACA, and OVRO
telescopes.
Treatment of the primary beam depends critically on parameters
set in sm.setvp() and sm.setoptions(ftmachine) - see help
sm.setvp for details. For componentlists, if sm.setvp() is run
prior to predict, then the spectral variation of each component
in the componentlist will include the multiplicative term of
the beam value for each channel frequency. So a flat spectrum
component will show the frequency variation of the beam in the
predicted visibilities.
.. rubric:: Task output
Below is a list of the products produced by the **simobserve**
task. Not all of these will necessarily be produced, depending on
input parameters selected.
.. note:: **NOTE**: To support different runs with different arrays, the
names have the configuration name from antenna list appended.
- [project].[cfg].skymodel = 4D input sky model image
(optionally) scaled
- [project].[cfg].skymodel.flat.regrid.conv = input sky regridded
to match the output image, and convolved with the output clean
beam
- [project].[cfg].skymodel.png = diagnostic figure of sky model
with pointings
- [project].[cfg].ptg.txt = list of mosaic pointings
- [project].[cfg].quick.psf = psf calculated from uv coverage
- [project].[cfg].ms = noise-free MeasurementSet
- [project].[cfg].noisy.ms = corrupted MeasurementSet
- [project].[cfg].observe.png = diagnostic figure of uv coverage
and visibilities
- [project].[cfg].simobserve.last = saved input parameters for
**simobserve** task
.. rubric:: Parameter descriptions
*project*
The root filename for all output files. This parameter should be
set to the same name as used when running **simanalyze** or
**simalma** for the directory of results generated.
*skymodel*
The input image (used as a model of the sky). **simobserve** uses
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. **simobserve** 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:: **NOTE**: Setting those parameters simply changes the header
values, ignoring any values already in the image. No regridding
is performed.
You can also manipulate an image header manually with the
**imhead** task. If you have a proper Coordinate System,
**simobserve** will do its best to generate visibilities from
that.
.. rubric:: *skymodel* expandable parameters
*inbright*
Scales the model flux densities by setting the peak brightness of
the britest pixel in Jy/pixel, or '' for unchanged.
.. warning:: **WARNING**: '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*
The central direction to place the sky model image, or '' to use
whatever is in the image already.
*incell*
The spatial pixel size to scale the skymodel image, or '' to use
whatever is in the image already.
*incenter*
The frequency to use for the center channel (or only channel, if
the skymodel is 2D). Examples: *incenter='89GHz'*, or '' to use
what is in the header. This will also become the default rest frequency, e.g. when imaging with tclean.
*inwidth*
The width of the channels to use, or '' to use what is in the
image should be a string representing a quantity with units.
Examples: *inwidth='10MHz'*
.. note:: **NOTE**: *inwidth* only works reliably with frequencies, not
velocities.
.. note:: **NOTE** **2**: 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*
A component list model of the sky, added to or instead of
*skymodel*.
.. warning:: **WARNING**: **simobserve** does not currently handle component
lists correctly for single-dish-only simulations. It is advised
to convert the component list to an image or FITS file.
.. rubric:: complist expandable parameters
*compwidth*
The bandwidth of components; if simulating from components only,
this defines the bandwidth of the MS and output images.
*comp_nchan*
The number of channels in the output MS. Validated only for a
positive integer number of channels, this parameter assumes a flat
spectrum and equal spacing when setting the channel width in the
output MS. Since variation in channel width as a function of
frequency is not currently supported, it is not advised to use
this parameter to simulate observations with spectral index or
large fractional bandwidth (use a skymodel image instead).
*setpointings*
If True, **simobserve** calculates a map of pointings based on a
set of sub-parameters and generates a pointing file. If False, it
will read the pointings from the parameter *ptgfile*.
.. rubric:: *setpointings=True* expandable parameters
*integration*
Sets the time interval for each integration. Also used with
*setpointings=False*. Examples: *integration='10s'*
.. note:: **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*
The mosaic center direction. If left unset, **simobserve** will
use the center of the skymodel image. Examples: *direction= 'J2000
19h00m00 -40d00m00';* can optionally be a list of pointings,
otherwise **simobserve** will cover a region of size *mapsize*
according to *maptype*.
*mapsize*
The angular size of mosaic map to simulate. Set to '' to cover the
model image.
*maptype*
How to calculate the pointings for the mosaic observation.
'hexagonal', 'square' (rectangular raster), 'ALMA' for the same
hex algorithm as the ALMA Cycle 1 OT or 'ALMA2012' for the
algorithm used in the Cycle 0 OT.
*pointingspacing*
Spacing in between primary beams. "0.25PB" to use 1/4 of the
primary beam FWHM, "nyquist" will use :math:`\lambda/d/2`, '' will
use :math:`\lambda/d/\sqrt(3)` for INT, :math:`\lambda/d/3` for
SD.
.. rubric:: *setpointings=False* expandable parameters
*ptgfile*
A text file specifying directions in the following format, with
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:: **NOTE**: At this time the file should contain only science
pointings: **simobserve** will observe these, then optionally
the calibrator, then the list of science pointings again, etc,
until totaltime is used up.
*obsmode*
Sets the observation mode to calculate visibilities from a
skymodel image (which may have been modified above), an optional
component list, and a pointing file (which also may have been
generated above). This parameter takes two possible values:
- interferometer (or int)
- singledish (or sd)
If simulating from a component list, you should specify
*compwidth*, the desired bandwidth. There is not currently a way
to specify the spectrum of a component, so simulations from a
componentlist only will be continuum (1 chan).
.. rubric:: *obsmode* expandable parameters ('int' or 'sd')
*refdate*
The date of simulated observation. Examples:
*refdate='2014/05/21'*
*hourangle*
The hour angle of observation, given as a string of various
possible formats. E.g., "-3:00:00", or "5h". The default setting
for this parameter is *hourangle='transit'*, which is equivalent
to 0h.
*totaltime*
The total time of an observation. Examples: *totaltime='7200s'* or
if a number without units, interpreted as the number of times to
repeat the mosaic.
.. rubric:: *obsmode='int' expandable parameters*
*antennalist*
ASCII file containing antenna positions. Each row has x, y, and z
coordinates and antenna diameter and name; header lines are
required to specify the observatory name and coordinate system. If
the configuration file does not include antenna names, the station
name will be used instead.
::
#observatory=ALMA
#COFA=-67.75,-23.02
#coordsys=LOC (local tangent plane)
# uid___A002_Xdb6217_X55ec_target.ms
# x y z diam station ant
-5.850273514 -125.9985379 -1.590364043 12. A058 DA41
-19.90369337 52.82680653 -1.892119601 12. A023 DA42
13.45860758 -5.790196849 -2.087805181 12. A035 DA43
5.606192499 7.646657746 -2.087775605 12. A001 DA44
24.10057423 -25.95933768 -2.08466565 12. A036 DA45
Standard array configuration files are found in your CASA data
repository, os.getenv("CASAPATH").split()[0]+"/data/alma/simmos/".
A string of the form "alma;0.5arcsec" will be parsed into a full
12m ALMA configuration. If *antennalist=' '*, **simobserve** will
not produce an interferometric MS. If simulating total power
observations, be sure to accurately set the parameter
*sdantlist*.
*caldirection*
An unresolved calibrator can be observed interleaved with the
science pointings. The calibrator is implemented as a point source
clean component with this specified direction and
flux= *calflux*.
*calflux*
Sets the flux density for the calibrator. Default is set to
*calflux='1Jy'*.
.. rubric:: *obsmode='sd' expandable parameters*
*sdantlist*
Single-dish antenna position file. If simulating total power
observations, be sure to accurately set the
parameter *sdantlist*. If this parameter is left unset,
**simobserve** assumes the default configuration file for a single
dish simulation (even if the configuration file is explicitly
specified in *antennalist*). Default: *sdantlist='aca.tp.cfg'.*
*sdant*
The index of the antenna in the list to use for total power.
Defaults to the first antenna on the list (*sdant=0*).
Heterogeneous total power "arrays" are not currently supported.
*thermalnoise*
Adds thermal noise to the synthesized data. This parameter takes
two possible values (not including unset ' '):
- tsys-atm: J. Pardo's ATM library will be used to construct an
atmospheric profile for the ALMA site: altitude 5000m, ground
pressure 650mbar, relhum=20%, a water layer of *user_pwv* at
altitude of 2km, the sky brightness temperature returned by
ATM, and internally tabulated receiver temperatures
- tsys-manual: instead of using the ATM model, specify the zenith
sky brightness and opacity manually. Noise is added and then
the visibility flux scale is referenced above the atmosphere.
In either mode, noise is calculated using the following
assumptions:
- an antenna spillover efficiency of 0.96,
- taper of 0.86,
- surface accuracy of 25 and 300 microns for ALMA and EVLA,
respectively, using the Ruze formula for surface efficiency,
- correlator efficiencies of 0.95 and 0.91 for ALMA and EVLA, and
- receiver temperatures:
- for ALMA: 25, 30, 40, 42, 50, 50, 72, 135, 105, 230 K
interpolated between 35, 75, 110, 145, 185, 230, 345, 409,
675, 867 GHz
- for EVLA: 500, 70, 60, 55, 100, 130, 350 K interpolated
between 0.33, 1.47, 4.89, 8.44, 22.5, 33.5, 43.3 GHz
- for SMA: 67, 116, 134, 500 K interpolated between 212, 310,
383, 660 GHz
These are only approximate numbers and do not take into account
performance at edges of receiver bands, nor are they guaranteed to
reflect the most recent measurements. Caveat emptor. Use the
**sm** tool to add noise if you want more precise control, and use
the ALMA exposure time calculator for sensitivity numbers in
proposals.
.. rubric:: *thermalnoise* expandable parameters
*t_ground*
The ambient ground/spillover temperature in K.
*seed*
Random number seed for noise generation.
.. rubric:: *thermalnoise='tsys-atm'* expandable parameters
*user_pwv*
The precipitable water vapor at zenith if constructing an
atmospheric model.
*thermalnoise='tsys-manual'* expandable parameters
*t_sky*
The atmospheric temperature in K.
*tau0*
The zenith opacity at observing frequency. See
`here <https://casaguides.nrao.edu/index.php/Corrupt>`__ for more
information on noise, in particular how to add a phase screen
using the toolkit.
*leakage*
Adds cross polarization corruption of this fractional magnitude.
*graphics*
View plots on the screen, saved to file, both, or neither.
*verbose*
Turns on or off the printing of extra information to the logger
and terminal.
*overwrite*
Overwrites existing files in the project subdirectory. Default:
False
.. _Examples:
Examples
This example was taken from the simulation CASAguide located
`here <https://casaguides.nrao.edu/index.php/Simulation_Guide_Component_Lists_(CASA_5.1)>`__.
::
default("simobserve")
project = "FITS_list"
skymodel = "Gaussian.fits"
inwidth = "1GHz"
complist = 'point.cl'
compwidth = '1GHz'
direction = "J2000 10h00m00.0s -30d00m00.0s"
obsmode = "int"
antennalist = 'alma.cycle5.1.cfg'
totaltime = "28800s"
mapsize = "10arcsec"
thermalnoise = ''
simobserve()
This example demonstrates the use of the *comp_nchan* parameter to
simulate a disk and produce a multi-channel MS (with a flat
spectrum).
::
simobserve(project="test_project",
complist="complist.cl",
compwidth="2000.00MHz",
comp_nchan=128,
integration="6.05s",
mapsize=['11.51arcsec'],
hourangle="1.5h",
totaltime="677.6s",
antennalist="antennalist.cfg2",
sdantlist="aca.tp.cfg",
thermalnoise="")
This example shows how to assign a central rest-frequency and channel width to a simulated image cube.
::
simobserve(project=‘model_cube’,
skymodel=‘skymodel.image',
inwidth='0.4MHz',
antennalist='alma.cycle6.1.cfg',
direction="J2000 16h59m41.63s -40d03m43.61s",
obsmode="int", mapsize="2arcmin",
totaltime="1800s",
thermalnoise='',
incenter='86.6425GHz')
This produces a data cube with a central rest-frequency of 86.6425 GHz and a channel width of 0.4 MHz. Note the `Known Issue for simobserve <../../notebooks/introduction.ipynb#Known-Issues>`__ that inwidth should not be specified in km/s.
.. _Development:
Development
No additional development details
.. _Details:
Parameter Details
Detailed descriptions of each function parameter
.. _project:
| ``project (string='sim')`` - root prefix for output file names
.. _skymodel:
| ``skymodel (string='')`` - Model image to observe
| * simobserve uses 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.
| * simobserve 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.
| * You can also manipulate an image header manually
| with the "imhead" task.
| * If you have a proper Coordinate System,
| simobserve will do its best to generate
| visibilities from that.
.. _inbright:
| ``inbright (string='')`` - Peak brightness to scale the image to, in Jy/pixel
| Subparameter of skymodel
| Default: '' (i.e., unchanged)
| Example: inbright='1.2Jy/pixel'
| 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:
| ``indirection (string='')`` - Central direction to place the sky model image
| Subparameter of skymodel
| Default: '' (use whatever is in the image
| already)
| Example: indirection='J2000 19h00m00
| -40d00m00'
.. _incell:
| ``incell (string='')`` - set new cell/pixel size
| Subparameter of skymodel
| Default: '' (use whatever is in the image
| already)
| Example: incell='0.1arcsec'
.. _incenter:
| ``incenter (string='')`` - Frequency to use for the center channel (or only channel,
| if the skymodel is 2D).
| Subparameter of skymodel
| Default: '' (use whatever is in the image
| already)
| This will also become the default rest frequency, e.g. when imaging with tclean.
| Example: incenter='89GHz'
.. _inwidth:
| ``inwidth (string='')`` - Set new channel width
| Subparameter of skymodel
| Default: '' (use whatever is in the image
| already)
|
| Should be a string representing a quantity with
| units e.g. inwidth='10MHz'
| NOTES:
| * Only works reliably with frequencies, not
| velocities
| * 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:
| ``complist (string='')`` - Component list model of the sky, added to or instead of skymodel.
.. _compwidth:
| ``compwidth (string='"8GHz"')`` - Bandwidth of components
| Subparameter of complist
| If simulating from components only, this defines
| the bandwidth of the MS and output images
| Example: compwidth='8GHz'
.. _comp_nchan:
| ``comp_nchan (int=1)`` - Channelization of components
| Subparameter of complist
| If simulating from components only, this defines
| the number of channels of the MeasurementSet
| Example: comp_nchan=256
.. _setpointings:
| ``setpointings (bool=True)`` - If true, calculate a map of pointings and write ptgfile. If false, read pointings from ptgfile.
| Default: True
| If graphics are on, display the pointings shown
| on the model image
.. _ptgfile:
| ``ptgfile (string='$project.ptg.txt')`` - A text file specifying directions
| Subparameter of setpointings=False
|
| The text file should have the following format,
| with optional integration times:
| 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: simobserve will observe these,
| then optionally the calibrator, then the list of
| science pointings again, etc, until totaltime is
| used up.
.. _integration:
| ``integration (string='10s')`` - Time interval for each integration
| Subparameter of setpointings=False
| Example: integration='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:
| ``direction (stringVec='')`` - Mosaic center direction.
| Subparameter of setpointings=True
| Example: "J2000 19h00m00 -40d00m00" or "" to
| center on model
| 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:
| ``mapsize (stringVec=['', ''])`` - Angular size of of mosaic map to simulate.
| Subparameter of setpointings=True
| Set to "" to cover model
.. _maptype:
| ``maptype (string='hexagonal')`` - How to calculate the pointings for the mosaic
| observation?
| Subparameter of setpointings=True
| Options: hexagonal, square (raster), ALMA, etc
| "ALMA" for the same hex algorithm as the ALMA
| Cycle 1 OT or "ALMA2012" for the algorithm used
| in the Cycle 0 OT
.. _pointingspacing:
| ``pointingspacing (string='')`` - Spacing in between pointings.
| Subparameter of setpointings=True
| Examples:
| pointingspacing="0.25PB"
| pointingspacing="" for ALMA default
| INT=lambda/D/sqrt(3), SD=lambda/D/3
.. _caldirection:
| ``caldirection (string='')`` - pt source calibrator [experimental]
.. _calflux:
| ``calflux (string='1Jy')`` - pt source calibrator flux [experimental]
.. _obsmode:
| ``obsmode (string='int')`` - Observation mode to simulate
| Options: int(interferometer)|sd(singledish)|""(none)
| Observation mode to calculate visibilities from a
| skymodel image (which may have been modified
| above), an optional component list, and a
| pointing file (which also may have been generated
| above).
| This parameter takes two possible values:
| - interferometer (or int)
| - singledish (or sd)
| * If graphics are on, this observe step will
| display the array (similar to plotants), the uv
| coverage, the synthesized (dirty) beam, and
| ephemeris information
| * If simulating from a component list, you should
| specify "compwidth", the desired bandwidth; and
| specify "comp_nchan", the desired channelization
| if more than one output channel is desired
.. _refdate:
| ``refdate (string='2014/01/01')`` - Date of simulated observation
| Subparameter of obsmode='int|sd'
| Not critical unless concatting simulations
| Example: refdate="2014/05/21"
.. _hourangle:
| ``hourangle (string='transit')`` - Hour angle of observation center.
| Subparameter of obsmode='int|sd'
| Examples:
| hourangle="-3:00:00", "5h", or "transit"
.. _totaltime:
| ``totaltime (string='7200s')`` - Total time of observation or number of repetitions
| Subparameter of obsmode='int|sd'
| Example:
| totaltime='7200s'
| If a number without units, interpreted as the
| number of times to repeat the mosaic.
.. _antennalist:
| ``antennalist (string='')`` - Text file containing antenna positions.
| Subparameter of obsmode='int|""'
| Each row has x y z coordinates and antenna diameter
| with optional station name and antenna name.
| Header lines are required to specify:
| # observatory=ALMA
| # coordsys=UTM
| If the Universal Transverse Mercator projection is
| specified, then other keywords are required:
| # datum=WGS84
| # zone=19
| # hemisphere=S
| If the observatory keyword is not defined, then the
| COFA keyword should be, using a coordinate pair:
| #COFA=-67.75,-23.02
| * Standard array configurations are found in your
| CASA data repository,
| * If "", simobserve will not not produce an
| interferometric MS
| * A string of the form "alma;0.5arcsec" will be
| parsed into a full 12m ALMA configuration.
.. _sdantlist:
| ``sdantlist (string='aca.tp.cfg')`` - single dish antenna position file
| Subparameter of obsmode='sd|""'
.. _sdant:
| ``sdant (int=0)`` - Index of the antenna in the list to use for total power.
| Subparameter of obsmode='sd|""'
| Default: first antenna on the list.
.. _outframe:
| ``outframe (string='LSRK')`` - spectral frame of MS to create
| Subparameter of obsmode='sd|""'
.. _thermalnoise:
| ``thermalnoise (string='tsys-atm')`` - add thermal noise.
| Options: tsys-atm, tsys-manual, ""
| This parameter accepts two settings:
| - tsys-atm: J. Pardo's ATM library will be used
| to construct an atmospheric profile for the ALMA
| site: altitude 5000m, ground pressure 650mbar,
| relhum=20%, a water layer of user_pwv at altitude
| of 2km, the sky brightness temperature returned
| by ATM, and internally tabulated receiver
| temperatures.
| - tsys-manual: instead of using the ATM model,
| specify the zenith sky brightness and opacity
| manually. Noise is added and then the visibility
| flux scale is referenced above the atmosphere.
| If left unset (empty string) no thermalnoise
| corruption is performed.
|
| In either mode, noise is calculated using an
| antenna spillover efficiency of 0.96, taper of
| 0.86, surface accuracy of 25 and 300 microns for
| ALMA and EVLA respectively (using the Ruze
| formula for surface efficiency), correlator
| efficiencies of 0.95 and 0.91 for ALMA and EVLA,
| receiver temperatures
| for ALMA of 17, 30, 37, 51, 65,
| 83,147,196,175,230 K interpolated between 35,
| 75,110,145,185,230,345,409,675,867 GHz,
| for EVLA of 500, 70, 60, 55, 100, 130, 350 K
| interpolated between
| 0.33,1.47,4.89,8.44,22.5,33.5,43.3 GHz,
| for SMA of 67, 116, 134, 500 K interpolated
| between 212.,310.,383.,660. GHz.
| Note: These are only approximate numbers and do
| not take into account performance at edges of
| receiver bands, neither are they guaranteed to
| reflect the most recent measurements. Caveat
| emptor. Use the sm tool to add noise if you want
| more precise control, and use the ALMA exposure
| time calculator for sensitivity numbers in
| proposals.
.. _user_pwv:
| ``user_pwv (double=0.5)`` - Precipitable water vapor if constructing an atmospheric
| model (in mm)
| Subparameter of thermalnoise='tsys-atm'
.. _t_ground:
| ``t_ground (double=270.)`` - Ground/spillover temperature in K
| Subparameter of
| thermalnoise='tsys-atm|tsys-manual'
.. _t_sky:
| ``t_sky (double=260.)`` - Atmospheric temperature in K
| Subparameter of thermalnoise='tsys-manual'
.. _tau0:
| ``tau0 (double=0.1)`` - Zenith opacity at observing frequency
| Subparameter of thermalnoise='tsys-manual'
| See the Simulations CASA Guide (https://casaguides.nrao.edu) on 'Corrupting Simulated Data' for more information on noise, in particular how to add a phase screen using the toolkit
.. _seed:
| ``seed (int=11111)`` - Random number seed
| Subparameter of
| thermalnoise='tsys-atm|tsys-manual'
.. _leakage:
| ``leakage (double=0.0)`` - add cross polarization corruption of this fractional
| magnitude (interferometer only)
.. _graphics:
| ``graphics (string='both')`` - View plots on the screen, saved to file, both, or neither
| Options: screen|file|both|none
.. _verbose:
| ``verbose (bool=False)`` - Print extra information to the logger and terminal
| Default: False
| Options: True|False
.. _overwrite:
| ``overwrite (bool=True)`` - Overwrite files starting with $project
| Default: False
| Options: True|False
"""
pass