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simobserve for ATCA

PostPosted: Fri Jul 31, 2020 9:09 pm
by bnorfolk
Hi all,

I'm attempting to pass a radiative transfer model synthetic image through simobserve in CASA in order to measure the residuals between my 34GHz transition disk image (obs on 04/05/16) and a "degraded" synthetic image.

I feel confident with most of the options in the task except for estimating the noise, I know the phase noise option covers any possible cloud cover ect. and setting that to True is fine, but I'm not sure how estimate the thermal noise.

Obviously this needs to be set to manual (thermalnoise='tsys-manual') as ATCA doesn't satisfy the ATM library by J. Pardo's for an atmospheric profile of the ALMA site (thermalnoise='tsys-atm'). The manual entries are the sky temperature at said frequency (t_sky), and the zenith opacity at said frequency (tau0).

Any tips on these variables or advice on the whole process would be greatly appreciated.

Cheers,
Brodie

Re: simobserve for ATCA

PostPosted: Mon Aug 03, 2020 12:01 pm
by Mark.Wieringa
Hi Brodie,

Unfortunately I don't have much to offer here. There was an attempt to get the Miriad opacity code into CASA 5 years ago, but it doesn't look like it is easily accessible from the user level.
The atcafiller tool has an opacities function, but I'm not sure how to get the corresponding Tsky.
You can get to the atcafiller tool (in casa 5) like this:

Code: Select all
from taskinit import casac
atf = casac.atcafiller()
help(atf.opacities)

Help on method opacities in module __casac__.atcafiller:

opacities(self, *args, **kwargs) unbound __casac__.atcafiller.atcafiller method
    opacities(self, fghz, tempk=300.0, humi=50.0, press=1010.0, height=200.0) -> std::vector< double >
   
   
   
    Summary
            Calculate opacity correction
   
   
    Description
   
    This function does the actual filling of the data from rpfits format
    files to a MeasurementSet. You may want to run select before fill, to
    reduce the amount of data you read in.
   
   
   
    Input Parameters:
            fghz             array of frequencies
            tempk            surface temperature in K 300.0
            humi             humidity in % 50.0
            press            surface pressure in hPa 1010.0
            height           observatory height in m 200.0
   
    Example:
   
    #
    atf = atcafiller()
    opac=atf.opacities([22.0,23.0],300.,50.,1013.,200.)
    print opac
    del atf



Cheers,

Mark

Re: simobserve for ATCA

PostPosted: Mon Aug 03, 2020 4:08 pm
by bnorfolk
Thanks Mark, any help is greatly appreciated.