simobserve – visibility simulation task – simulation task

Description

This task simulates interferometric or total power measurment sets It is currently optimized for JVLA and ALMA, although many observatories are included, and adding your own is simply a matter of providing an antenna location file (see below).

simobserve is meant to work in conjunction with the simanalyze task - Calling simobserve one more times will produce simulated measurement set(s), which are then gridded, inverted and deconvolved into output simulated images using simanalyze.

ALMA users are encouraged to use the simalma task, which provides additional information on the multiple simobserve and simanalyze calls required to simulate an ALMA observation which may consist of 12m interferometric, 7m interferometric, and 12m total power data.

More information and examples are availible at

http://casaguides.nrao.edu/index.php?title=Simulating_Observations_in_CASA

Please contact CASA experts with any questions.

Parameters

Title

Parameter	Default	Description
project	'sim'
skymodel	''	model image to observe
inbright	''
indirection	''
incell	''
incenter	''
inwidth	''
complist	''
compwidth	'"8GHz"'
setpointings	True
ptgfile	'$project.ptg.txt'
integration	'10s'
direction	numpy.array( [  ] )
mapsize	numpy.array( [ '','' ] )
maptype	'hexagonal'
pointingspacing	''
caldirection	''
calflux	'1Jy'
obsmode	'int'
refdate	'2014/01/01'
hourangle	'transit'
totaltime	'7200s'
antennalist	''
sdantlist	'aca.tp.cfg'
sdant	int(0)
outframe	'LSRK'
thermalnoise	'tsys-atm'
user_pwv	float(0.5)
t_ground	float(270.)
t_sky	float(260.)
tau0	float(0.1)
seed	int(11111)
leakage	float(0.0)
graphics	'both'
verbose	False
overwrite	True

Parameter Explanations

project

'sim'

root prefix for output file names

skymodel

''

• 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

''

scale surface brightness of brightest pixel e.g. “1.2Jy/pixel”

indirection

''

set new direction e.g. “J2000 19h00m00 -40d00m00”

incell

''

set new cell/pixel size e.g. “0.1arcsec”

incenter

''

set new frequency of center channel e.g. “89GHz” (required even for 2D model)

inwidth

''

set new channel width e.g. “10MHz” (required even for 2D model)

complist

''

componentlist to observe

compwidth

'"8GHz"'

bandwidth of components

setpointings

True

ptgfile

'$project.ptg.txt'

list of pointing positions

integration

'10s'

integration (sampling) time

direction

numpy.array( [  ] )

“J2000 19h00m00 -40d00m00” or “” to center on model

mapsize

numpy.array( [ '','' ] )

angular size of map or “” to cover model

maptype

'hexagonal'

hexagonal, square (raster), ALMA, etc

pointingspacing

''

spacing in between pointings or “0.25PB” or “” for ALMA default INT=lambda/D/sqrt(3), SD=lambda/D/3

caldirection

''

pt source calibrator [experimental]

calflux

'1Jy'

obsmode

'int'

observation mode to simulate [int(interferometer)|sd(singledish)|””(none)]

refdate

'2014/01/01'

date of observation - not critical unless concatting simulations

hourangle

'transit'

hour angle of observation center e.g. “-3:00:00”, “5h”, “-4.5” (a number without units will be interpreted as hours), or “transit”

totaltime

'7200s'

total time of observation or number of repetitions

antennalist

''

interferometer antenna position file

sdantlist

'aca.tp.cfg'

single dish antenna position file

sdant

int(0)

single dish antenna index in file

outframe

'LSRK'

spectral frame of MS to create

thermalnoise

'tsys-atm'

add thermal noise: [tsys-atm|tsys-manual|””]

user_pwv

float(0.5)

Precipitable Water Vapor in mm

t_ground

float(270.)

ambient temperature

t_sky

float(260.)

atmospheric temperature

tau0

float(0.1)

zenith opacity

seed

int(11111)

random number seed

leakage

float(0.0)

cross polarization (interferometer only)

graphics

'both'

display graphics at each stage to [screen|file|both|none]

verbose

False

overwrite

True

overwrite files starting with $project