Difference between revisions of "CASA Contributed Script: vlacal-setjy"

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(Created page with "<div style="background-color: salmon"> <div style="background-color: salmon; margin: 20px"> <br> This page is currently under development. Please do not use this guide until t...")
 
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== Introduction ==
 
Flux-density calibration for the VLA typically involves an observation of one of four primary calibrators: 3C286, 3C48, 3C138 and 3C147. Models for these sources are distributed as part of the CASA package and model visibilities are predicted using the task [https://casadocs.readthedocs.io/en/stable/api/tt/casatasks.imaging.setjy.html setjy]. The most current models available in  
 
Flux-density calibration for the VLA typically involves an observation of one of four primary calibrators: 3C286, 3C48, 3C138 and 3C147. Models for these sources are distributed as part of the CASA package and model visibilities are predicted using the task [https://casadocs.readthedocs.io/en/stable/api/tt/casatasks.imaging.setjy.html setjy]. The most current models available in  
 
[https://casadocs.readthedocs.io/en/stable/api/tt/casatasks.imaging.setjy.html setjy] are accessible using the flux-density standard [https://iopscience.iop.org/article/10.3847/1538-4365/aa6df9 Perley Butler 2017] (hereafter PB17), which is based on observations conducted on or before January 2016.  
 
[https://casadocs.readthedocs.io/en/stable/api/tt/casatasks.imaging.setjy.html setjy] are accessible using the flux-density standard [https://iopscience.iop.org/article/10.3847/1538-4365/aa6df9 Perley Butler 2017] (hereafter PB17), which is based on observations conducted on or before January 2016.  
  
Given the significant, recent variability in some primary calibrators (i.e., 3C48 and 3C147) NRAO staff are creating a new flux-density standard based on more recent observations.  Instead of packaging these new models with CASA, NRAO will host a database that is continually updated with the latest monitoring data which will have an approximately monthly cadence. A new flux-density standard will be added to the task [https://casadocs.readthedocs.io/en/stable/api/tt/casatasks.imaging.setjy.html setjy]  to make use of these new models (estimated release date 2023). Until the new version of [https://casadocs.readthedocs.io/en/stable/api/tt/casatasks.imaging.setjy.html setjy] is released, this contributed script vlacal-setjy.py can be executed to obtain the newest models from the database.  This casaguide provides documentation and examples of how to use this script.
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Given the recent and significant variability in some primary calibrators (i.e., 3C48 and 3C147) NRAO staff are in the process of creating a new flux-density standard based on more recent observations.  Instead of packaging these new models with CASA, NRAO will host a database that is continually updated with the latest monitoring data (having an approximately monthly cadence). A new flux-density standard will be added to the task [https://casadocs.readthedocs.io/en/stable/api/tt/casatasks.imaging.setjy.html setjy]  to make use of these new models (estimated release date 2023). Until the new version of [https://casadocs.readthedocs.io/en/stable/api/tt/casatasks.imaging.setjy.html setjy] is released, this contributed script vlacal-setjy.py can be executed to obtain the newest models from the database.  This casaguide provides documentation and examples of how to use this script.
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== Obtaining the script ==
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The script [http://www.aoc.nrao.edu/~jmarvil/vlacal-setjy.py vlacal-setjy.py is available for download here].  Please save a copy in your local working directory, e.g.,
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<source lang="python">
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# in CASA
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!wget www.aoc.nrao.edu/~jmarvil/vlacal-setjy.py
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</source>
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== Loading the functions ==
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Next, you will want to run the script in CASA, e.g.,
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<source lang="python">
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# in CASA
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execfile('vlacal-setjy.py')
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</source>
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This will import functions that you can now run from your CASA session.  You will need to run the script each time you start CASA if you want these functions to be available (or add the above to [https://casadocs.readthedocs.io/en/latest/api/configuration.html?highlight=startup.py#startup-py startup.py]). Note that you will not need to open the script in an editor or make any modifications to it.

Revision as of 16:00, 31 October 2021


This page is currently under development. Please do not use this guide until this message has been removed.


Introduction

Flux-density calibration for the VLA typically involves an observation of one of four primary calibrators: 3C286, 3C48, 3C138 and 3C147. Models for these sources are distributed as part of the CASA package and model visibilities are predicted using the task setjy. The most current models available in setjy are accessible using the flux-density standard Perley Butler 2017 (hereafter PB17), which is based on observations conducted on or before January 2016.

Given the recent and significant variability in some primary calibrators (i.e., 3C48 and 3C147) NRAO staff are in the process of creating a new flux-density standard based on more recent observations. Instead of packaging these new models with CASA, NRAO will host a database that is continually updated with the latest monitoring data (having an approximately monthly cadence). A new flux-density standard will be added to the task setjy to make use of these new models (estimated release date 2023). Until the new version of setjy is released, this contributed script vlacal-setjy.py can be executed to obtain the newest models from the database. This casaguide provides documentation and examples of how to use this script.


Obtaining the script

The script vlacal-setjy.py is available for download here. Please save a copy in your local working directory, e.g.,

# in CASA
!wget www.aoc.nrao.edu/~jmarvil/vlacal-setjy.py


Loading the functions

Next, you will want to run the script in CASA, e.g.,

# in CASA
execfile('vlacal-setjy.py')

This will import functions that you can now run from your CASA session. You will need to run the script each time you start CASA if you want these functions to be available (or add the above to startup.py). Note that you will not need to open the script in an editor or make any modifications to it.