Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/research/workshops/2011/ALMA/Villard_ALMA_simulations.pdf Дата изменения: Wed May 18 07:15:18 2011 Дата индексирования: Tue Feb 5 13:02:47 2013 Кодировка: Поисковые слова: п п п п п

Simula'ng observa'ons with ALMA
Eric Villard (ALMA JAO)


simdata is a CASA task
· · · · · · · simdata replaces simdata2, star'ng from 3.1 inp simdata, to list the parameters default simdata, to reset the parameters go simdata, to run, or simply go if ac've task tget simdata, to load parameters help simdata, to obtain the online help simdata is a wrapper to the sm tool
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simdata is structured
· simdata has 6 subtasks, run in the order:
1. 2. 3. 4. 5. 6. modifymodel setpoin'ngs predict thermalnoise image analyze

· The output of each subtask can be re used in subsequent runs.
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modifymodel
skymodel inbright indirec'on incell incenter inwidth # # # # # # model image to observe or modify set peak surface brightness e.g. "1.2Jy/pixel" or "" "J2000 19h00m00 40d00m00" or "" cell/pixel size e.g. "0.1arcsec" or "" frequency of center channel e.g. "89GHz" or "" channel width e.g. "10MHz" or ""

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setpoin'ngs
integra'on direc'on mapsize maptype poin'ngspacing # # # # # integra'on (sampling) 'me "J2000 19h00m00 40d00m00" or "" to center on model angular size of map or "" to cover model hexagonal, square, etc spacing in between poin'ngs or "" for 0.5 PB

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predict
complist compwidth antennalist refdate total'me caldirec'on calflux sdantlist sdant # # # # # # op'onal componentlist to observe with skymodel op'onal bandwidth if simula'ng from components only antenna posi'on file or "" for no interferometric MS 'me/date of observa'on *see help total 'me of observa'on pt source calibrator [experimental]

# single dish antenna pos. file or "" for no total power MS # single dish antenna index in file

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thermalnoise
thermalnoise = 'tsys atm' user_pwv # Precipitable Water Vapor in mm t_ground # ambient temperature OR thermal t_groun t_sky tau0 noise = 'tsys manual' d # ambient temperature # atmospheric temperature # zenith opacity

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image
vis modelimage imsize cell niter threshold weigh'ng mask outertaper stokes # # # # # # # # # # Measurement Set(s) to image prior image to use in clean e.g. exis'ng single dish image output image size in pixels (x,y) or 0 to match model cell size with units or "" to equal model maximum number of itera'ons (0 for dirty image) flux level (+units) to stop cleaning weigh'ng to apply to visibili'es clean mask see help clean uv taper on outer baselines in uv plane Stokes params to image

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analyze
showarray showuv showpsf showmodel showconvolved showclean showresidual showdifference showfidelity # # # # # # # # # like plotants display uv coverage display synthesized (dirty) beam display sky model at original resolu'on display sky model convolved with output beam display the synthesized image display the clean residual image display difference image display fidelity

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3c288 at 240GHz (B6), with compact ES array (1)
taskname = 'simdata' default(taskname) project = 'sim' modifymodel = T skymodel = '3c288.fits' indirec'on = 'J2000 12h00m00 23d00m00' incenter = '240GHz' inwidth = '2GHz' direc'on = 'J2000 12h00m00 23d00m00' antennalist = 'CompactCycle0.txt ' total'me = '21600s' image = T niter = 0 weigh'ng = 'briggs' analyze = T showarray = T showconvolved = T showdifference = F showfidelity = F graphics = 'file' overwrite = T simdata()

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3c288 at 240GHz (B6), with compact ES array (2)

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3c288 at 350GHz (B7), with compact ES array (1)
taskname = 'simdata' default(taskname) project = 'sim2' modifymodel = T skymodel = '3c288.fits' indirec'on = 'J2000 12h00m00 23d00m00' incenter = '350GHz' inwidth = '2GHz' direc'on = 'J2000 12h00m00 23d00m00' mapsize = '' poin'ngspacing = '' antennalist = 'CompactCycle0.txt' total'me = '21600s' image = T niter = 0 weigh'ng = 'briggs' analyze = T showarray = T showconvolved = T showdifference = F showfidelity = F graphics = 'file' overwrite = T simdata()
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3c288 at 350GHz (B7), with compact ES array (2)

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Corrup'ng data with thermal noise
taskname = 'simdata' default(taskname) project = 'sim3' modifymodel = T skymodel = '3c288.fits' indirec'on = 'J2000 12h00m00 23d00m00' incenter = '350GHz' inwidth = '2GHz' direc'on = 'J2000 12h00m00 23d00m00' mapsize = '' poin'ngspacing = '' antennalist = 'ExtendedCycle0.txt' total'me = '21600s' thermalnoise = 'tsys atm' user_pwv = 5 image = T vis = '$project.noisy.ms' niter = 0 weigh'ng = 'briggs' analyze = T showarray = T showconvolved = T showdifference = F showfidelity = F graphics = 'file' overwrite = T simdata()

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Other possible data corrup'ons
· · · · · · · · · Anenua'on by the troposphere Atmospheric phase fluctua'ons Addi've random noise Constant cross polariza'on Fluctua'ons in complex receiver gain Bandpass shape Poin'ng errors Antenna dependent feed posi'on angle More informa'on at: hnps://safe.nrao.edu/wiki/pub/ALMA/ SimulatorCookbook/corruptguide.pdf
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Outputs of simdata
sim.diff/ sim.absdiff/ sim.fidelity/ sim.flux/ sim.image/ sim.image.flat/ sim.model/ sim.ms/ sim.psf/ sim.ptg.txt sim.quick.psf/ sim.residual/ sim.residual.flat/ sim.skymodel/ sim.skymodel.flat/ sim.skymodel.flat.regri sim.skymodel.flat.regri sim.absconv/ d/ d.conv/ Difference between 2d cleaned image and 2d input sky convolved with output synthesized beam Absolute of previous Fidelity image Clean flux image (clean components, not convolved with clean beam gaussian) Clean image Clean image moment 0 Clean components Simulated visibili'es Interferometric beam, full inversion with weigh'ng List of poin'ngs PSF from uv coverage, no weigh'ng Clean residual Clean residual moment 0 Original sky model (4d) Moment 0 of previous Previous regridded Previous convolved by output synthesized beam Absolute of previous

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For more informa'on:
hnp://casaguides.nrao.edu/index.php? 'tle=Main_Page#Simula'ng_Observa'ons

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