Difference between revisions of "EVLA 6cmWideband Tutorial SN2010FZ"

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and was run on 2010-07-11 from 21:28 to 22:28 UT (size 37.74GB).
 
and was run on 2010-07-11 from 21:28 to 22:28 UT (size 37.74GB).
  
For the purposes of this tutorial, we have provided the raw SDM data (as would be extracted from the archive) as well as measurement sets created by filling the data (with the importevla task) and upon time-averaging to 10s (after application of the online flags).   
+
For the purposes of this tutorial, we have provided the raw SDM data (as would be extracted from the archive) as well as measurement sets created by filling the data (with the {{importevla}} task) and upon time-averaging to 10s (after application of the online flags).   
  
 
To start your tutorial, depending on which dataset you start with, proceed to:
 
To start your tutorial, depending on which dataset you start with, proceed to:
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For the purposes of this tutorial, we assume that the SDM is resident on disk, in this case at the location
 
For the purposes of this tutorial, we assume that the SDM is resident on disk, in this case at the location
<pre>/lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065</pre>.   
+
<tt>/lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065</tt>.   
 
Use the actual location of your data when you carry out the commands.
 
Use the actual location of your data when you carry out the commands.
  
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</source>
 
</source>
  
Here we had the task create (but not apply) the online flagging commands, plus flags for zero-clipping and shadowing.  The timeranges for the online flags were extended by 1.5sec (the integration time was 1sec) to account for some timing mismatches present in the EVLA data at this time.  These online flags indicated times where the antennas were not on source (e.g. slewing) or had other detectable faults. The created flagging commands will be stored in the <pre>FLAG_CMD</pre> MS table and can be applied later.  Note that if you set <pre>applyflags=True</pre> here then after filling the task will go ahead and apply the flags for you.  
+
Here we had the task create (but not apply) the online flagging commands, plus flags for zero-clipping and shadowing.  The timeranges for the online flags were extended by 1.5sec (the integration time was 1sec) to account for some timing mismatches present in the EVLA data at this time.  These online flags indicated times where the antennas were not on source (e.g. slewing) or had other detectable faults. The created flagging commands will be stored in the <tt>FLAG_CMD</tt> MS table and can be applied later.  Note that if you set <tt>applyflags=True</tt> here then after filling the task will go ahead and apply the flags for you.  
  
For the purposes of this exercise, in order to save time and disk space, we have turned off the automatic creation of flag column backups by setting <pre>flagbackup=False</pre>.  If we make a mistake and need to recover flags then we will have to rerun all previous commands.  We recommend that for real data processing that you leave the default value <pre>flagbackup=True</pre> in this and subsequent tasks.
+
For the purposes of this exercise, in order to save time and disk space, we have turned off the automatic creation of flag column backups by setting <pre>flagbackup=False</pre>.  If we make a mistake and need to recover flags then we will have to rerun all previous commands.  We recommend that for real data processing that you leave the default value <tt>flagbackup=True</tt> in this and subsequent tasks.

Revision as of 12:41, 25 August 2011

Overview

This article describes the calibration and imaging of a single-pointing 6cm EVLA wideband continuum dataset on the galaxy NGC2967 (UGC5180) which was the location of the supernova candidate SN2010FZ. No supernova was detected in this observation, but the galactic continuum emission from this face-on spiral is adequately imaged. The data were taken in RSRO mode, with 1024 MHz of bandwidth in each of two widely spaced basebands (comprised each of 8 128 MHz spectral windows), spanning 4.5 to 7.5 GHz. We will use wideband imaging techniques in this tutorial.

This is a more advanced tutorial, and if you are a relative novice (and particularly for EVLA continuum calibration and imaging), it is strongly recommended that you start with the EVLA Continuum Tutorial 3C391 before tackling this dataset. We will not include basic information on CASA processing in this tutorial.

CASA Versions

This tutorial was written for the CASA Version 3.2.1 (release r15198 26 May 2011).

Obtaining the Data

The scheduling block (SB) processed appears in the EVLA archive under program AS1015 as AS1015_sb1658169_1.55388.89474846065 and was run on 2010-07-11 from 21:28 to 22:28 UT (size 37.74GB).

For the purposes of this tutorial, we have provided the raw SDM data (as would be extracted from the archive) as well as measurement sets created by filling the data (with the importevla task) and upon time-averaging to 10s (after application of the online flags).

To start your tutorial, depending on which dataset you start with, proceed to:

  • To start with the raw SDM data: Start with the section below titled "Importing your EVLA data from SDM". This is where you would start if you were reducing data from the archive.
  • To start with the raw filled MS: Start with the section below titled "Application of Online Flags and averaging your MS".
  • To start with the flagged and averaged MS: Start with the section below titled "Examining and Flagging your averaged MS".

Importing your EVLA data from SDM

For the purposes of this tutorial, we assume that the SDM is resident on disk, in this case at the location /lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065. Use the actual location of your data when you carry out the commands.

The listsdm task will print out a summary of the scans, fields, spectral windows, and antennas present in your SDM.

# In CASA
listsdm('/lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065')

We use the importevla task to convert the SDM dataset from the archive to a CASA Measurement Set (MS).

# In CASA
importevla(asdm='/lustre/smyers/AS1015/AS1015_sb1658169_1.55388.89474846065', \
           vis='SN2010FZ_filled.ms',online=True,flagzero=True, \
           shadow=True,applyflags=False,tbuff=1.5,flagbackup=False)

Here we had the task create (but not apply) the online flagging commands, plus flags for zero-clipping and shadowing. The timeranges for the online flags were extended by 1.5sec (the integration time was 1sec) to account for some timing mismatches present in the EVLA data at this time. These online flags indicated times where the antennas were not on source (e.g. slewing) or had other detectable faults. The created flagging commands will be stored in the FLAG_CMD MS table and can be applied later. Note that if you set applyflags=True here then after filling the task will go ahead and apply the flags for you.

For the purposes of this exercise, in order to save time and disk space, we have turned off the automatic creation of flag column backups by setting

flagbackup=False

. If we make a mistake and need to recover flags then we will have to rerun all previous commands. We recommend that for real data processing that you leave the default value flagbackup=True in this and subsequent tasks.