EVLA 3-bit Tutorial G192 - CASA4.1

From CASA Guides
Jump to: navigation, search

This is an advanced Jansky VLA data reduction tutorial that calibrates and images a 3-bit dataset.

This CASA Guide is for CASA version 4.1.0.

Overview

This article describes the calibration and imaging of the protostar G192.16-3.84. The data were taken in Ka-band using the VLA's 3-bit samplers and widely-spaced basebands centered at 29 and 36.5 GHz. Each baseband has over 4 GHz of bandwidth comprised of 32 128-MHz spectral windows. In this tutorial, we will examine, flag, and calibrate the data, including the the corrections for the requantizer gains (which are necessary for 3-bit data calibration and harmless on 8-bit data). We will then image and analyze the calibrated data, using wideband imaging techniques.

This is a more advanced tutorial, so if you are a relative novice (and particularly for VLA continuum calibration and imaging), it is strongly recommended that you start with the EVLA Continuum Tutorial 3C391 (at least read it through) before proceeding with this tutorial.

In addition, on the MainPage of the CASA Guides you can find these helpful pages:

In this tutorial we will be invoking the tasks as function calls. You can cut and paste these to your casapy session. We also recommend that you copy all the commands you use, with any relevant commentary, to a text file. This is very good practice when tackling large datasets. If you wish, you can use the Script Extractor to create a file with the tutorial commands, which can subsequently be edited and annotated as desired.

Occasionally we will be setting Python variables (e.g., as lists for flags) outside the function call so make sure you set those before running the task command. Note that when you call a CASA task as a function, any task parameters that are not set in the function call will be used with their default values. This means they will not use values you set in any previous calls or outside the call. See Getting_Started_in_CASA#Task_Execution for more on calling tasks and setting parameters in the scripting interface.

NOTE: If you find that the figures on the right margin of the browser window overlap the text too much and make reading difficult, you can adjust the width of the browser window.

Obtaining the Data

The data for this tutorial were taken with the VLA as part of its commissioning phase. They comprise the scheduling block (SB) TVER0004.sb14459364.eb14492359.56295.26287841435, which was run on 2013-01-03 from 6:18 to 7:47 UT (its raw size is 57.04 GB).

The data can be downloaded directly from http://casa.nrao.edu/Data/EVLA/G192/G192_6s.ms.tar.gz (dataset size: 18 GB)

Your first step will be to unzip and untar the file in a terminal (before you start CASA):

tar -xzvf G192_6s.ms.tar.gz

If you are brave enough, you can also get the data directly from the VLA archive. Go to the NRAO Science Data Archive, and search for "TVER0004.sb14459364" in the Archive File ID field. Then select the dataset and choose a time-averaging value of 6 seconds. (Although the data were taken in A-configuration, we will not be imaging outside of the center of the field, so we aren't too worried about time-average smearing and will take advantage of averaging to reduce the dataset size.) Also select the "Create tar file" option.

In addition, only the fields used for analysis and observation are included in the downloadable file. This can be accomplished using the split task in CASA:

# In CASA
split('TVER0004.sb14459364.eb14492359.56295.26287841435.ms', outputvis='G192_6s.ms', \
      datacolumn='all', field='3,6,7,10', keepflags=False, spw='2~65')

(If you're downloading from the archive and feeling ambitious, you could also select only the scans with fields 3, 6, 7, and 10 in the "Select scans for MS or AIPS FITS" box.) This will create a file equivalent to what is used at the start of this tutorial.

Finally, you will need to modify some information in the SOURCE and FIELD tables of the measurement set (this has already been done for you in the file available for download, but must be done by hand if obtaining from the archive). Follow the instructions here to make these changes.

Starting CASA

To start CASA, type:

casapy

This will run a script to initialize CASA, setting paths appropriately. It will also start writing to a file called ipython-<unique-stamp>.log, which will contain a record of all the text you enter at the CASA prompt, as well as casapy-<unique-stamp>.log, which will contain all the messages that are printed to the CASA logger window.

A logger window will also appear. Note that you can rescale this window or change the font size as desired (the latter is under "View").

Examining the MS

We use listobs to summarize our MS:

# In CASA
listobs('G192_6s.ms', listfile='G192_listobs.txt')

This will write the output to a file called G192_listobs.txt, which we can print to the terminal using the cat command:

# In CASA
cat G192_listobs.txt
================================================================================
           MeasurementSet Name:  /lustre/mkrauss/casa_guides/3bit/G192_6s.ms      MS Version 2
================================================================================
   Observer: Dr. Debra Shepherd     Project: uid://evla/pdb/7303457  
Observation: EVLA
Data records: 10061248       Total integration time = 4557 seconds
   Observed from   03-Jan-2013/06:31:51.0   to   03-Jan-2013/07:47:48.0 (UTC)

   ObservationID = 0         ArrayID = 0
  Date        Timerange (UTC)          Scan  FldId FieldName             nRows     SpwIds   Average Interval(s)    ScanIntent
  03-Jan-2013/06:31:48.0 - 06:36:42.0     6      0 3c147-J0542+49         1019200  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 5.94, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [CALIBRATE_FLUX#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:46:15.0 - 06:46:54.0    10      1 gcal-J0603+174          145600  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57, 5.57] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:47:09.0 - 06:47:54.0    11      2 G192.16-3.84            163200  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65, 5.65] [OBSERVE_TARGET#UNSPECIFIED]
              06:48:06.0 - 06:48:39.0    12      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:48:51.0 - 06:49:39.0    13      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              06:49:51.0 - 06:50:24.0    14      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:50:36.0 - 06:51:24.0    15      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              06:51:36.0 - 06:52:09.0    16      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:52:19.5 - 06:53:09.0    17      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              06:53:21.0 - 06:53:54.0    18      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:54:06.0 - 06:54:54.0    19      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              06:55:06.0 - 06:55:39.0    20      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:55:51.0 - 06:56:39.0    21      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              06:56:51.0 - 06:57:24.0    22      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:57:36.0 - 06:58:24.0    23      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              06:58:36.0 - 06:59:12.0    24      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              06:59:21.0 - 07:00:12.0    25      2 G192.16-3.84            187200  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67] [OBSERVE_TARGET#UNSPECIFIED]
              07:00:19.5 - 07:00:57.0    26      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:01:06.0 - 07:01:57.0    27      2 G192.16-3.84            187200  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67] [OBSERVE_TARGET#UNSPECIFIED]
              07:02:03.0 - 07:02:42.0    28      1 gcal-J0603+174          125184  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99, 5.99] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:02:48.0 - 07:03:36.0    29      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:03:48.0 - 07:04:21.0    30      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:04:33.0 - 07:05:21.0    31      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:05:33.0 - 07:06:06.0    32      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:06:18.0 - 07:07:06.0    33      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:07:18.0 - 07:07:51.0    34      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:08:03.0 - 07:08:51.0    35      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:09:03.0 - 07:09:36.0    36      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:09:48.0 - 07:10:36.0    37      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:10:46.5 - 07:11:21.0    38      1 gcal-J0603+174          123200  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49, 5.49] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:11:33.0 - 07:12:21.0    39      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:12:33.0 - 07:13:06.0    40      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:13:18.0 - 07:14:06.0    41      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:14:16.5 - 07:14:51.0    42      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:15:01.5 - 07:15:51.0    43      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:16:03.0 - 07:16:36.0    44      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:16:48.0 - 07:17:39.0    45      2 G192.16-3.84            187200  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67] [OBSERVE_TARGET#UNSPECIFIED]
              07:17:48.0 - 07:18:24.0    46      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:18:33.0 - 07:19:24.0    47      2 G192.16-3.84            187200  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67, 5.67] [OBSERVE_TARGET#UNSPECIFIED]
              07:19:30.0 - 07:20:09.0    48      1 gcal-J0603+174          124864  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:20:18.0 - 07:21:06.0    49      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:21:15.0 - 07:21:48.0    50      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:22:00.0 - 07:22:48.0    51      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:23:00.0 - 07:23:33.0    52      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:23:45.0 - 07:24:33.0    53      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:24:45.0 - 07:25:18.0    54      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:25:30.0 - 07:26:18.0    55      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:26:30.0 - 07:27:03.0    56      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:27:15.0 - 07:28:03.0    57      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:28:15.0 - 07:28:48.0    58      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:29:00.0 - 07:29:48.0    59      2 G192.16-3.84            166400  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [OBSERVE_TARGET#UNSPECIFIED]
              07:30:00.0 - 07:30:33.0    60      1 gcal-J0603+174          124800  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5, 5.5] [CALIBRATE_AMPLI#UNSPECIFIED, CALIBRATE_PHASE#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
              07:40:27.0 - 07:47:51.0    64      3 3c84-J0319+413         1537600  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]  [6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6] [CALIBRATE_BANDPASS#UNSPECIFIED, OBSERVE_TARGET#UNSPECIFIED]
           (nRows = Total number of rows per scan) 
Fields: 4
  ID   Code Name                RA               Decl           Epoch   SrcId      nRows
  0    E    3c147-J0542+49      05:42:36.137916 +49.51.07.23356 J2000   0        1019200
  1    D    gcal-J0603+174      06:03:09.130269 +17.42.16.81070 J2000   1        3264448
  2    NONE G192.16-3.84        05:58:13.540000 +16.31.58.30001 J2000   2        4240000
  3    F    3c84-J0319+413      03:19:48.160102 +41.30.42.10305 J2000   3        1537600
Spectral Windows:  (64 unique spectral windows and 1 unique polarization setups)
  SpwID  Name            #Chans   Frame   Ch1(MHz)  ChanWid(kHz)  TotBW(kHz) BBC Num  Corrs          
  0      EVLA_KA#A1C1#2     128   TOPO   34476.000      1000.000    128000.0      10  RR  LL
  1      EVLA_KA#A1C1#3     128   TOPO   34604.000      1000.000    128000.0      10  RR  LL
  2      EVLA_KA#A1C1#4     128   TOPO   34732.000      1000.000    128000.0      10  RR  LL
  3      EVLA_KA#A1C1#5     128   TOPO   34860.000      1000.000    128000.0      10  RR  LL
  4      EVLA_KA#A1C1#6     128   TOPO   34988.000      1000.000    128000.0      10  RR  LL
  5      EVLA_KA#A1C1#7     128   TOPO   35116.000      1000.000    128000.0      10  RR  LL
  6      EVLA_KA#A1C1#8     128   TOPO   35244.000      1000.000    128000.0      10  RR  LL
  7      EVLA_KA#A1C1#9     128   TOPO   35372.000      1000.000    128000.0      10  RR  LL
  8      EVLA_KA#A1C1#10    128   TOPO   35500.000      1000.000    128000.0      10  RR  LL
  9      EVLA_KA#A1C1#11    128   TOPO   35628.000      1000.000    128000.0      10  RR  LL
  10     EVLA_KA#A1C1#12    128   TOPO   35756.000      1000.000    128000.0      10  RR  LL
  11     EVLA_KA#A1C1#13    128   TOPO   35884.000      1000.000    128000.0      10  RR  LL
  12     EVLA_KA#A1C1#14    128   TOPO   36012.000      1000.000    128000.0      10  RR  LL
  13     EVLA_KA#A1C1#15    128   TOPO   36140.000      1000.000    128000.0      10  RR  LL
  14     EVLA_KA#A1C1#16    128   TOPO   36268.000      1000.000    128000.0      10  RR  LL
  15     EVLA_KA#A1C1#17    128   TOPO   36396.000      1000.000    128000.0      10  RR  LL
  16     EVLA_KA#A2C2#18    128   TOPO   36476.000      1000.000    128000.0      11  RR  LL
  17     EVLA_KA#A2C2#19    128   TOPO   36604.000      1000.000    128000.0      11  RR  LL
  18     EVLA_KA#A2C2#20    128   TOPO   36732.000      1000.000    128000.0      11  RR  LL
  19     EVLA_KA#A2C2#21    128   TOPO   36860.000      1000.000    128000.0      11  RR  LL
  20     EVLA_KA#A2C2#22    128   TOPO   36988.000      1000.000    128000.0      11  RR  LL
  21     EVLA_KA#A2C2#23    128   TOPO   37116.000      1000.000    128000.0      11  RR  LL
  22     EVLA_KA#A2C2#24    128   TOPO   37244.000      1000.000    128000.0      11  RR  LL
  23     EVLA_KA#A2C2#25    128   TOPO   37372.000      1000.000    128000.0      11  RR  LL
  24     EVLA_KA#A2C2#26    128   TOPO   37500.000      1000.000    128000.0      11  RR  LL
  25     EVLA_KA#A2C2#27    128   TOPO   37628.000      1000.000    128000.0      11  RR  LL
  26     EVLA_KA#A2C2#28    128   TOPO   37756.000      1000.000    128000.0      11  RR  LL
  27     EVLA_KA#A2C2#29    128   TOPO   37884.000      1000.000    128000.0      11  RR  LL
  28     EVLA_KA#A2C2#30    128   TOPO   38012.000      1000.000    128000.0      11  RR  LL
  29     EVLA_KA#A2C2#31    128   TOPO   38140.000      1000.000    128000.0      11  RR  LL
  30     EVLA_KA#A2C2#32    128   TOPO   38268.000      1000.000    128000.0      11  RR  LL
  31     EVLA_KA#A2C2#33    128   TOPO   38396.000      1000.000    128000.0      11  RR  LL
  32     EVLA_KA#B1D1#34    128   TOPO   26976.000      1000.000    128000.0      13  RR  LL
  33     EVLA_KA#B1D1#35    128   TOPO   27104.000      1000.000    128000.0      13  RR  LL
  34     EVLA_KA#B1D1#36    128   TOPO   27232.000      1000.000    128000.0      13  RR  LL
  35     EVLA_KA#B1D1#37    128   TOPO   27360.000      1000.000    128000.0      13  RR  LL
  36     EVLA_KA#B1D1#38    128   TOPO   27488.000      1000.000    128000.0      13  RR  LL
  37     EVLA_KA#B1D1#39    128   TOPO   27616.000      1000.000    128000.0      13  RR  LL
  38     EVLA_KA#B1D1#40    128   TOPO   27744.000      1000.000    128000.0      13  RR  LL
  39     EVLA_KA#B1D1#41    128   TOPO   27872.000      1000.000    128000.0      13  RR  LL
  40     EVLA_KA#B1D1#42    128   TOPO   28000.000      1000.000    128000.0      13  RR  LL
  41     EVLA_KA#B1D1#43    128   TOPO   28128.000      1000.000    128000.0      13  RR  LL
  42     EVLA_KA#B1D1#44    128   TOPO   28256.000      1000.000    128000.0      13  RR  LL
  43     EVLA_KA#B1D1#45    128   TOPO   28384.000      1000.000    128000.0      13  RR  LL
  44     EVLA_KA#B1D1#46    128   TOPO   28512.000      1000.000    128000.0      13  RR  LL
  45     EVLA_KA#B1D1#47    128   TOPO   28640.000      1000.000    128000.0      13  RR  LL
  46     EVLA_KA#B1D1#48    128   TOPO   28768.000      1000.000    128000.0      13  RR  LL
  47     EVLA_KA#B1D1#49    128   TOPO   28896.000      1000.000    128000.0      13  RR  LL
  48     EVLA_KA#B2D2#50    128   TOPO   28976.000      1000.000    128000.0      14  RR  LL
  49     EVLA_KA#B2D2#51    128   TOPO   29104.000      1000.000    128000.0      14  RR  LL
  50     EVLA_KA#B2D2#52    128   TOPO   29232.000      1000.000    128000.0      14  RR  LL
  51     EVLA_KA#B2D2#53    128   TOPO   29360.000      1000.000    128000.0      14  RR  LL
  52     EVLA_KA#B2D2#54    128   TOPO   29488.000      1000.000    128000.0      14  RR  LL
  53     EVLA_KA#B2D2#55    128   TOPO   29616.000      1000.000    128000.0      14  RR  LL
  54     EVLA_KA#B2D2#56    128   TOPO   29744.000      1000.000    128000.0      14  RR  LL
  55     EVLA_KA#B2D2#57    128   TOPO   29872.000      1000.000    128000.0      14  RR  LL
  56     EVLA_KA#B2D2#58    128   TOPO   30000.000      1000.000    128000.0      14  RR  LL
  57     EVLA_KA#B2D2#59    128   TOPO   30128.000      1000.000    128000.0      14  RR  LL
  58     EVLA_KA#B2D2#60    128   TOPO   30256.000      1000.000    128000.0      14  RR  LL
  59     EVLA_KA#B2D2#61    128   TOPO   30384.000      1000.000    128000.0      14  RR  LL
  60     EVLA_KA#B2D2#62    128   TOPO   30512.000      1000.000    128000.0      14  RR  LL
  61     EVLA_KA#B2D2#63    128   TOPO   30640.000      1000.000    128000.0      14  RR  LL
  62     EVLA_KA#B2D2#64    128   TOPO   30768.000      1000.000    128000.0      14  RR  LL
  63     EVLA_KA#B2D2#65    128   TOPO   30896.000      1000.000    128000.0      14  RR  LL
Sources: 256
  ID   Name                SpwId RestFreq(MHz)  SysVel(km/s) 
  0    3c147-J0542+49      0     -              -            
  0    3c147-J0542+49      1     -              -            
  0    3c147-J0542+49      2     -              -            
  0    3c147-J0542+49      3     -              -            
  0    3c147-J0542+49      4     -              -            
  0    3c147-J0542+49      5     -              -            
  0    3c147-J0542+49      6     -              -            
  0    3c147-J0542+49      7     -              -            
  0    3c147-J0542+49      8     -              -            
  0    3c147-J0542+49      9     -              -            
  0    3c147-J0542+49      10    -              -            
  0    3c147-J0542+49      11    -              -            
  0    3c147-J0542+49      12    -              -            
  0    3c147-J0542+49      13    -              -            
  0    3c147-J0542+49      14    -              -            
  0    3c147-J0542+49      15    -              -            
  0    3c147-J0542+49      16    -              -            
  0    3c147-J0542+49      17    -              -            
  0    3c147-J0542+49      18    -              -            
  0    3c147-J0542+49      19    -              -            
  0    3c147-J0542+49      20    -              -            
  0    3c147-J0542+49      21    -              -            
  0    3c147-J0542+49      22    -              -            
  0    3c147-J0542+49      23    -              -            
  0    3c147-J0542+49      24    -              -            
  0    3c147-J0542+49      25    -              -            
  0    3c147-J0542+49      26    -              -            
  0    3c147-J0542+49      27    -              -            
  0    3c147-J0542+49      28    -              -            
  0    3c147-J0542+49      29    -              -            
  0    3c147-J0542+49      30    -              -            
  0    3c147-J0542+49      31    -              -            
  0    3c147-J0542+49      32    -              -            
  0    3c147-J0542+49      33    -              -            
  0    3c147-J0542+49      34    -              -            
  0    3c147-J0542+49      35    -              -            
  0    3c147-J0542+49      36    -              -            
  0    3c147-J0542+49      37    -              -            
  0    3c147-J0542+49      38    -              -            
  0    3c147-J0542+49      39    -              -            
  0    3c147-J0542+49      40    -              -            
  0    3c147-J0542+49      41    -              -            
  0    3c147-J0542+49      42    -              -            
  0    3c147-J0542+49      43    -              -            
  0    3c147-J0542+49      44    -              -            
  0    3c147-J0542+49      45    -              -            
  0    3c147-J0542+49      46    -              -            
  0    3c147-J0542+49      47    -              -            
  0    3c147-J0542+49      48    -              -            
  0    3c147-J0542+49      49    -              -            
  0    3c147-J0542+49      50    -              -            
  0    3c147-J0542+49      51    -              -            
  0    3c147-J0542+49      52    -              -            
  0    3c147-J0542+49      53    -              -            
  0    3c147-J0542+49      54    -              -            
  0    3c147-J0542+49      55    -              -            
  0    3c147-J0542+49      56    -              -            
  0    3c147-J0542+49      57    -              -            
  0    3c147-J0542+49      58    -              -            
  0    3c147-J0542+49      59    -              -            
  0    3c147-J0542+49      60    -              -            
  0    3c147-J0542+49      61    -              -            
  0    3c147-J0542+49      62    -              -            
  0    3c147-J0542+49      63    -              -            
  1    gcal-J0603+174      0     -              -            
<snip>        
  2    G192.16-3.84        0     -              -            
<snip>        
  3    3c84-J0319+413      63    -              -            
Antennas: 26:
  ID   Name  Station   Diam.    Long.         Lat.                Offset from array center (m)                ITRF Geocentric coordinates (m)        
                                                                     East         North     Elevation               x               y               z
  0    ea01  N48       25.0 m   -107.37.38.1  +33.59.06.2       -855.2759     9405.9595      -25.9351 -1600374.885000 -5036704.201000  3562667.881900
  1    ea02  N56       25.0 m   -107.37.47.9  +34.00.38.4      -1105.2071    12254.3069      -34.2426 -1600128.383400 -5035104.146500  3565024.672100
  2    ea03  N16       25.0 m   -107.37.10.9  +33.54.48.0       -155.8511     1426.6436       -9.3827 -1601061.956000 -5041175.880700  3556058.037600
  3    ea05  W08       25.0 m   -107.37.21.6  +33.53.53.0       -432.1184     -272.1472       -1.5070 -1601614.092200 -5042001.650900  3554652.508900
  4    ea06  N32       25.0 m   -107.37.22.0  +33.56.33.6       -441.7237     4689.9748      -16.9332 -1600781.042100 -5039347.435200  3558761.533000
  5    ea07  E40       25.0 m   -107.32.35.4  +33.52.16.9       6908.8279    -3240.7316       39.0057 -1595124.924100 -5045829.461500  3552210.685200
  6    ea09  E24       25.0 m   -107.35.13.4  +33.53.18.1       2858.1754    -1349.1257       13.7290 -1598663.097500 -5043581.389700  3553767.027800
  7    ea10  E32       25.0 m   -107.34.01.5  +33.52.50.3       4701.6588    -2209.7063       25.2191 -1597053.120700 -5044604.691600  3553059.009300
  8    ea11  W56       25.0 m   -107.44.26.7  +33.49.54.6     -11333.2153    -7637.6824       15.3542 -1613255.404300 -5042613.085000  3548545.901400
  9    ea12  E08       25.0 m   -107.36.48.9  +33.53.55.1        407.8285     -206.0065       -3.2272 -1600801.926000 -5042219.366500  3554706.448200
  10   ea13  W24       25.0 m   -107.38.49.0  +33.53.04.0      -2673.3434    -1784.5870       10.4960 -1604008.742800 -5042135.827600  3553403.728800
  11   ea14  W16       25.0 m   -107.37.57.4  +33.53.33.0      -1348.7083     -890.6269        1.3068 -1602592.853600 -5042055.005300  3554140.703900
  12   ea15  W72       25.0 m   -107.48.24.0  +33.47.41.2     -17419.4730   -11760.2869       14.9578 -1619757.314900 -5042937.673700  3545120.385300
  13   ea16  N08       25.0 m   -107.37.07.5  +33.54.15.8        -68.9252      433.1901       -5.0683 -1601147.956700 -5041733.824100  3555235.952500
  14   ea17  E48       25.0 m   -107.30.56.1  +33.51.38.4       9456.5938    -4431.6366       37.9317 -1592894.088800 -5047229.121000  3551221.221100
  15   ea18  E72       25.0 m   -107.24.42.3  +33.49.18.0      19041.8754    -8769.2059        4.7234 -1584460.867200 -5052385.599300  3547599.997600
  16   ea19  W64       25.0 m   -107.46.20.1  +33.48.50.9     -14240.7600    -9606.2738       17.1055 -1616361.584300 -5042770.519200  3546911.442800
  17   ea20  N72       25.0 m   -107.38.10.5  +34.04.12.2      -1685.6775    18861.8403      -43.4734 -1599557.932000 -5031396.371000  3570494.760600
  18   ea21  E64       25.0 m   -107.27.00.1  +33.50.06.7      15507.6045    -7263.7280       67.1961 -1587600.190400 -5050575.873800  3548885.396600
  19   ea22  N24       25.0 m   -107.37.16.1  +33.55.37.7       -290.3745     2961.8582      -12.2374 -1600930.087700 -5040316.398500  3557330.387000
  20   ea23  N64       25.0 m   -107.37.58.7  +34.02.20.5      -1382.3750    15410.1463      -40.6373 -1599855.675100 -5033332.371000  3567636.622500
  21   ea24  W40       25.0 m   -107.41.13.5  +33.51.43.1      -6377.9740    -4286.7919        8.2191 -1607962.456900 -5042338.214500  3551324.943600
  22   ea25  W48       25.0 m   -107.42.44.3  +33.50.52.1      -8707.9407    -5861.7854       15.5265 -1610451.925400 -5042471.123100  3550021.056800
  23   ea26  W32       25.0 m   -107.39.54.8  +33.52.27.2      -4359.4561    -2923.1223       11.7579 -1605808.647100 -5042230.071500  3552459.203400
  24   ea27  E16       25.0 m   -107.36.09.8  +33.53.40.0       1410.0316     -673.4696       -0.7909 -1599926.110000 -5042772.967300  3554319.791200
  25   ea28  N40       25.0 m   -107.37.29.5  +33.57.44.4       -633.6167     6878.5984      -20.7748 -1600592.764000 -5038121.352000  3560574.847300

This task displays a lot of information about the MS. We can see that the observation was performed with the EVLA, and the included integration time is 4557 seconds (1.3 hour). The number of data records (10,061,248) is approximately equal to the number of baselines (N_antenna * [N_antenna - 1] / 2) X the number of integrations (observing time / time-average binning) X the number of spectral windows. For this observation, this is roughly 325 baselines (26X25/2) X 760 integrations (4557s total/6s avg) X 64 spectral windows = 15,808,000. Note that this is high by ~50%; this is because the "total time" reported is simply (start time) - (end time) of the MS, which includes periods of flagged data and scans that were excluded from the final MS. Extra exercise: examine the MS using browsetable to see what a data record looks like (equivalent to a row, as displayed by this task).

The most useful parts of the listobs output are the scan, field, and spectral window listings. From the spectral window information, we can see that there are a total of 64 (0 through 63) spectral windows in this dataset, each with 128 channels, and that they are all at Ka-band (which spans 26.5 - 40.0 GHz).

The field listing shows four sources:

  • 3C147 (Field ID 0), the flux calibration source;
  • J0603+174 (1), used for calibrating the complex gains;
  • G192.16-3.84 (2), the science target; and
  • 3C84 (3), used for calibrating the spectral bandpass.

Note the rapid switching between G192 and J0603: this will help us accurately perform and transfer the gain phase for these high-frequency data. There was also a pointing calibration source in the original MS, but since this calibration was already applied during observing, we did not retain this source (in the interests of limiting dataset size).

Flagging the MS

online flags plotted from flagcmd

The online flags, which are a record of known bad data produced by the VLA online system, were applied by the archive when it generated the MS. However, it's good to have a sense of what was deleted in this process. A record of the flags is stored in a table in the MS called FLAG_CMD. (In fact, the information for this table is actually a subdirectory within the MS; you can see this by listing the contents of G192_6s.ms.)

You can examine the commands stored in the FLAG_CMD table using flagcmd:

# In CASA
flagcmd(vis='G192_6s.ms', inpmode='table', action='list', \
        useapplied=True)
  • useapplied=True: tells the task to list flags that have already been applied to the MS (which includes all online flags; otherwise, they would be ignored)

The flag information will be printed to the logger (all 2870 rows). The majority of the flags are "ANTENNA_NOT_ON_SOURCE" -- most of these were generated as a result of the fast switching between G192 and the phase calibrator.

You can also plot the commands stored in the FLAG_CMD table:

# In CASA
myrows = range(2868)
flagcmd(vis='G192_6s.ms', inpmode='table', action='plot', \
        useapplied=True, tablerows=myrows)

Note that we are only plotting the first 2868 rows. This is because the last two are from flagging zeros in the data (caused by correlator errors) and data which have been flagged due to antenna shadowing. (Since the data were taken in the most widely spaced A-configuration, little if any data were likely affected by shadowing.) Note that you can omit the tablerows selection and plot those too -- you will just get lines at the bottom marked as "All" antennas for these flags.

By default, this will bring up a matplotlib plotter. You can have it plot to a PNG file instead:

# In CASA
flagcmd(vis='G192_6s.ms', inpmode='table', action='plot', tablerows=myrows, 
        useapplied=True, plotfile='PlotG192_flagcmd_4.1.png')

The flags as plotted in the figure to the above right look normal. They are color-coded by REASON, and you see the ANTENNA_NOT_ON_SOURCE flags between scans, some FOCUS_ERROR flags here and there, and the occasional SUBREFLECTOR_ERROR flag also between scans (most likely after band changes when the subreflector rotates to pick up the new feed on the ring, some are slower than others). You want to be wary of long blocks of unexpected flags, which might be false alarms and cause you to flag too much data. In that case, look at the data itself in plotms (see below for examples) to decide whether or not to apply all flags. (Note: for the dataset in this tutorial, we have already deleted all the flagged data to reduce the file size, so you won't be able to inspect the flagged data within the MS. To do so, you will need to download the original dataset from the NRAO Science Data Archive.)

plotants plotter

To plot up the antenna positions in the array:

# In CASA
plotants('G192_6s.ms')

NOTE: if after this point (or any other) you get "table locks", which may occur erroneously and are sometimes triggered by plotting tasks, use clearstat to clear them:

# In CASA
clearstat

Now we examine the MS looking for bad data to flag. We will use plotms to bring up an interactive GUI that will display 2-D Y vs. X style line plots. NOTE: We do not recommend using the editing/flagging features of plotms. It is very easy to mess up your data this way. Also, to improve speed we will be restricting the scope of plotting, so most box/flag operations would not get rid of all the bad data -- although they would appear to delete it, which is misleading.

We will instead use plotms to identify bad data and then use flagcmd to flag it. This will also allow full scripting of the flagging, which is ultimately the best way to keep track of what's been deleted. Given the large dataset sizes now being generated, reproducibility is extremely important. Imagine spending a day flagging your data, then a disk error corrupts the MS: it's imperative that you have an automated way to regenerate your work! This is also why we also encourage you to keep a running file with all the commands you use to process a dataset.

NOTE: If you need an introduction to plotms, see:

WARNING: The Flag FlagThoseData.png button on the plotms GUI is close to other buttons you will be using, in particular the one that deletes boxes you have drawn DeleteBox.png. Be careful you don't hit the Flag button by mistake!

To get an idea of the data layout, plot a single baseline (ea02&ea05), channel (31, for all spectral windows), and polarization (RR) versus time. Note that limiting the selected data with appropriate filters is extremely helpful when plotting large datasets:

plotms of ea02&ea05 amp vs time
# In CASA
plotms(vis='G192_6s.ms', field='', spw='*:31~31', \
       antenna='ea02&ea05', xaxis='time', yaxis='amp', \
       correlation='rr', coloraxis='field')

Here, we can see the alternating phase calibration and science target scans, as well as the (brighter) bandpass calibrator at the end of the observation. Feel free to play with ways to view -- for example, you can change the size of the plotted points, if they are too small to see easily, by setting "Unflagged Points Symbol" to "Custom" and increasing the number of pixels under "Style".

plotms baseline amplitudes for field 3

Look for bad antennas by picking the bandpass calibrator and plotting baselines. We color the points by "antenna1" to see which antennas might be troublesome:

# In CASA
plotms(vis='G192_6s.ms', field='3', spw='*:31~31', \
       antenna='', xaxis='baseline',\
       yaxis='amp', coloraxis='antenna1')

You should be able to see that three of the antennas have lower amplitudes than the rest. Boxing with the Mark Regions MarkRegionsButton.png tool and using the Locate Casaplotms-locate-tool.png tool will show in the logger that these are antennas ea01, ea10 and ea19; indeed, checking the Operator Log for this observation shows that these antennas have collimation offsets and that the data have been corrupted. We will delete these antennas.

plotms field 3 ea05 and ea13 amp vs frequency

Now look at the raw spectral bandpasses of baselines to ea05. It is in the inner core of the array and a prospective reference antenna. Since we plan to flag them, we will exclude antennas ea01, ea10, and ea19 using negation (represented by "!") in the selection, and iterate by antenna:

# In CASA
plotms(vis='G192_6s.ms', field='3', \
       antenna='ea05;!ea01;!ea10;!ea19', \
       xaxis='frequency', yaxis='amp', 
       coloraxis='corr', iteraxis='antenna')

The plot for ea05 and ea13 shows that ea13's RCP is weak, as noted in the log file as well. We will flag this antenna, since current restrictions do not allow for single-polarization data to be imaged if it's part of a full-polarization dataset.

Also, note that spectral windows 16 through 31 for antenna ea18 look very suspicious. We need to keep an eye on these data.

For antenna ea24, there appear to be some issues with spectral windows 47 and 48, and the RCP of spw 40 also looks problematic, so we'll flag this as well.

plotms field 3 ea05 and ea18 phase vs frequency

Now plot the phases, iterating through baselines to ea05:

# In CASA
plotms(vis='G192_6s.ms', field='3', \
       antenna='ea05;!ea01;!ea10;!ea13;!ea19', \
       xaxis='frequency', yaxis='phase', \
       coloraxis='spw', iteraxis='antenna')

You see the slopes due to residual delays. Mostly a turn or less over a 128-MHz subband, but there are some outliers. Step through to ea18. You see that there are jumps between spectral windows for spw 16-31 (see plot on the right). This reinforces our suspicion that something is wrong with these data and we will flag them as well.

To carry out the flagging, we again use flagcmd in the mode where it takes a list of command strings:

# In CASA
flaglist = ['antenna="ea01,ea10,ea19,ea13"',
            'antenna="ea24" spw="40,47~48"',
            'antenna="ea18" spw="16~31"']
flagcmd(vis='G192_6s.ms', inpmode='list', inpfile=flaglist, \
        action='apply', flagbackup=True)

These commands will be carried out as well as being added to the FLAG_CMD table (marked as applied). Before applying the flags, a backup version will be stored as flagcmd_1, in case you would like to restore the flagged data to the MS (this can be done using flagmanager).

Plot the data again, now that is has been flagged:

# In CASA
plotms(vis='G192_6s.ms', field='3', antenna='ea05', \
       xaxis='frequency', yaxis='amp')
plotms field 3 ea05 amp vs frequency

Now let's look at our phase calibrator -- it is weaker, and we can see some RFI:

# In CASA
plotms(vis='G192_6s.ms', field='1', antenna='ea05', \
       xaxis='frequency', yaxis='amp', scan='10,20,30,40,50,60')

Note that we've chosen a subset of scans to limit the amount of data being plotted. This will give a sense of whether there was RFI (or other issues) present in the observation, but will obviously not display everything. Later on, when we plot the calibrated data, we will need to again inspect for possible bad data (and will iterate and recalibrate).

Use the Zoom button ZoomButton.png, Mark Regions MarkRegionsButton.png and Locate Casaplotms-locate-tool.png to identify the frequency/channels of the RFI. In particular, we note the following:

  • 27.228 GHz (spw 33 ch 124)
  • 27.707 GHz (spw 37 ch 91)
  • 27.81-27.811 GHz (spw 38 ch 66-67)
  • 27.819-27.821 GHz (spw 38 ch 75-77)
  • 28.894 GHz (spw 46 ch 126)
  • 28.976 GHz (spw 48 ch 0)
  • 29.684-20.685 GHz (spw 53 ch 68-69)
  • 30.976 GHz (spw 63 ch 80) very strong
  • 35.782 GHz (spw 10 ch 26)
  • 36.523 GHz (spw 15 ch 127)
  • 37.946 GHz (spw 27 ch 62)
  • 37.948 GHz (spw 27 ch 64)

Flag these channels:

# In CASA
flaglist = ['spw="33:124,37:91,38:66~67;75~77,46:126,48:0"', \
            'spw="53:68~69,63:80,10:26,15:127,27:62,27:64"']
flagcmd(vis='G192_6s.ms', inpmode='list', inpfile=flaglist, \
        action='apply', flagbackup=True)

When this is finished, it's useful to have a look at the flagged data. To reload the plotms window taking the new flags into account, check the "force reload" box and click on "Plot." (As a shortcut, you can also hold down the "Shift" key while clicking on the "Plot" button to force reload a plot.)

Finally, split off the good data, without retaining the flagged data. This will allow us to work on the data without having to start completely over (if we mess something up badly) as well as letting us do simpler data selections.

# In CASA
# Remove any existing split data, otherwise split will not happen
os.system('rm -rf G192_flagged_6s.ms')
split(vis='G192_6s.ms', outputvis='G192_flagged_6s.ms', \
      datacolumn='data', keepflags=False)
  • keepflags=False: again, to limit the size of the MS, we do not propagate flagged data to the split-off MS.

You now have a MS called G192_flagged_6s.ms in your working area. This should be 16GB in size, which you can see while still at the CASA command prompt by typing:

# In CASA
os.system('du -sh G192_flagged_6s.ms')

Note that the built-in system function allows one to execute UNIX shell commands within a CASA session. (Some, like ls, don't need this extra wrapper, but most are not automatically understood.)

plotms antenna2 vs. time "datastream" plot

At this point it is useful to plot a "datastream" view of the dataset to show what antennas are present at what time. You can do this using

# In CASA
plotms(vis='G192_flagged_6s.ms', xaxis='time', yaxis='antenna2', \
       plotrange=[-1,-1,0,26], coloraxis='field')

This shows the times where data is present on baselines TO a given Antenna2 (which means there is no line for ea01 which is antenna 0). You can pick up ea01 (and drop ea28) by setting yaxis='antenna1'. To the right we show this plot. You see that for the most part, the antennas are present for the entire observation. One exception to this is antenna ea16, which comes in a little late on the first scan of G192.

Calibration

Before proceeding with calibration, we will summarize the split flagged MS:

# In CASA
listobs('G192_flagged_6s.ms', listfile='G192_flagged_listobs.txt')

As before, cat'ing the file shows that there are now 6,958,621 data records present, and 22 antennas remaining in the MS.

Setting the flux density scale

It is now time to begin calibration. The general data reduction strategy is to derive a series of scaling factors or corrections from the calibrators, which, in addition with a priori calibration information, are collectively applied to the science data. For much more discussion of the philosophy, strategy, and implementation of calibration of synthesis data within CASA, see Synthesis Calibration in the CASA Cookbook and User Reference Manual .

Before calibrating, we insert a model for the flux calibration source 3C147 into the MS. In order to do this, we first have to locate the model image on our system with setjy, which we will also use to set the flux density scale. The setjy task has an option to list possible available model images:

# In CASA
setjy(vis='G192_flagged_6s.ms', listmodels=True)

which sends output to your terminal (but not the logger). For example, on an NRAO workstation:

No candidate modimages matching '*.im* *.mod*' found in .

Candidate modimages (*) in /usr/lib64/casapy/release/4.1.0/data/nrao/VLA/CalModels:
3C138_A.im  3C138_L.im	3C138_U.im  3C147_C.im	3C147_Q.im  3C147_X.im	3C286_K.im  3C286_S.im	3C48_A.im  3C48_L.im  3C48_U.im
3C138_C.im  3C138_Q.im	3C138_X.im  3C147_K.im	3C147_S.im  3C286_A.im	3C286_L.im  3C286_U.im	3C48_C.im  3C48_Q.im  3C48_X.im
3C138_K.im  3C138_S.im	3C147_A.im  3C147_L.im	3C147_U.im  3C286_C.im	3C286_Q.im  3C286_X.im	3C48_K.im  3C48_S.im  README

The relevant image for our purposes is 3C147_A.im, in the directory /usr/lib64/casapy/release/4.1.0/data/nrao/VLA/CalModels/. Your system may show a different location (for example /home/casa/data/nrao/VLA/CalModels/, or /Applications/CASA.app/Contents/data/nrao/VLA/CalModels on a Mac). Since it knows about this image, we only have to give the image name and not the entire path. Otherwise, you will need to give it the entire path.

We can now run the setjy task using the appropriate model:

# In CASA
setjy(vis='G192_flagged_6s.ms', field='0', scalebychan=True, \
      modimage='3C147_A.im')
plotms of model amp vs freq for 3C147
  • scalebychan=True: will fill the model with per-channel values; otherwise, setjy would use a single value per spectral window.
  • usescratch=False: put the model in the header instead of creating scratch columns in the MS. This will take up considerably less disk space.

We can plot the model data using plotms:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='0', antenna='ea02&ea05', \
       xaxis='freq', yaxis='amp', ydatacolumn='model')

Inspecting the logger report shows that 3C147 is about 0.98 Jy at the lower end of the band to 0.67 Jy at the upper end.

Deriving a priori calibrations

Some calibration products are carried along throughout the calibration process and used as priors for subsequent calibration steps. These include the antenna position corrections, gain-elevation curves, tropospheric opacity corrections, and requantizer gains.

Antenna position corrections

We use gencal to determine any antenna-position corrections that need to be applied to the data. This is based on a database of corrections with the time they were determined and when they were applied by the observing system, compared to the times in your observations.

# In CASA
gencal('G192_flagged_6s.ms', caltable='calG192.antpos', \
       caltype='antpos', antenna='')

You should see in the logger:

No offsets found for this MS
*** Warning *** No offsets found. No caltable created.
gencal::::casa	An error occurred running task gencal.

Although it looks like the task has failed, reading the warning and error show that in fact, there simply aren't any antenna corrections to apply (despite the fact the fact that the Observer Log lists antennas as having recently moved).

Gain-elevation curves

In CASA 4.1, we have the option to use gencal to create calibration tables containing the gain curves and tropospheric opacity corrections for the antennas. Although you can still use the gaincurve=True and opacity options in the calibration tasks, we will make use of this new feature (note that the gaincurve=True will be phased out in future CASA releases):

# In CASA
gencal('G192_flagged_6s.ms', caltable='calG192.gaincurve', \
       caltype='gc')

Tropospheric opacity corrections

plotweather output

The opacity of the observation can be computed from a seasonal model and/or weather station information. We will use the plotweather task to display the weather information and to calculate the zenith opacities for each spectral window. After the zenith opacities are derived, gencal will recompute for the correct elevation of the data automatically using e^{(-\csc[el]\tau_z)} to create the opacity-correction calibration table.

To start, we want to plot the opacity of the atmosphere at the time this observation was taken so it can be corrected for in subsequent calibrations. plotweather plots the weather conditions at the time of observation and calculates the atmospheric opacities based on these data, in combination with a seasonal model that contains long-term statistics at the VLA site. Using seasonal_weight=0.5 (the default value) gives both equal weights:

We will be running plotweather in a way that will assign the opacity list (one entry for each spectral window in ascending order) to the variable myTau:

# In CASA
myTau = plotweather(vis='G192_flagged_6s.ms', doPlot=T)

The logger should display:

##########################################
##### Begin Task: plotweather        #####
plotweather(vis="G192_flagged_6s.ms",seasonal_weight=0.5,doPlot=True,plotName="")
2013-06-18 21:47:00 INFO plotweather	SPW : Frequency (GHz) : Zenith opacity (nepers)
 0  :   34.476  :  0.03
 1  :   34.604  :  0.031
 2  :   34.732  :  0.031
 3  :   34.860  :  0.031
 4  :   34.988  :  0.032
<snip>
61  :   30.640  :  0.024
62  :   30.768  :  0.024
63  :   30.896  :  0.024
wrote weather figure: G192_flagged_6s.ms.plotweather.png
##### End Task: plotweather          #####
##########################################

It also creates a file G192_flagged_6s.ms.plotweather.png with the elevation of the sun, the wind speed and direction, the temperature, precipitable water vapor (PWV) as functions of time over the observation (view this file with your preferred image viewer like gthumb, xv or Preview), and assigns the myTau variable to the full list of opacities per spectral window.

We can now create a calibration table for the opacities with gencal using the calmode='opac' parameter. We could input the opacities directly, but it's easier to use the myTau variable with a little Python:

# In CASA
SPWs = []
for window in range(0,64):
    SPWs.append(str(window))
# In CASA
spwString = ','.join(SPWs)
gencal(vis='G192_flagged_6s.ms', caltable='calG192.opacity',
       caltype='opac', spw=spwString, parameter=myTau)

Requantizer gain corrections

Finally, we will use gencal to create a calibration table containing corrections for the requantizer gains. Although this is only necessary for 3-bit data, such as our G192 dataset, it can be done for 8-bit datasets without any ill effects. For 3-bit data, this step is needed to account for the small gain changes (~5-10%) that result from resetting the quantizer gains as the correlator changes to a new 3-bit configuration. (Here is more information on observing with the 3-bit system.)

# In CASA
gencal('G192_flagged_6s.ms', caltable='calG192.requantizer', \
       caltype='rq')

The caltables we have generated (calG192.gaincurve, calG192.opacity, and calG192.requantizer) will need to be pre-applied in subsequent calibration steps.

Calibrating delays and initial bandpass solutions

plotcal G0 phase ant 0~15
plotcal G0 phase ant 16~26
plotcal K0 delay vs. antenna
plotcal B0 bandpass amp ant ea06 spw 0-31
plotcal B0 bandpass amp ant ea06 spw 32-63

First, we do a phase-only calibration solution on a narrow range of channels near the center of each spectral window on the bandpass calibrator 3C84 to flatten them with respect to time before solving for the bandpass. The range 60~68 should work. Pick a reference antenna near the center of the array -- ea05 is a reasonable choice (see above):

# In CASA
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G0', \
        field='3', spw='*:60~68', \
        gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                   'calG192.opacity'], \
        gaintype='G', refant='ea05', calmode='p', \
        solint='int', minsnr=3)
  • refant='ea05' : use ea05 as the reference antenna
  • solint='int' : do a per-integration solve (every 6 seconds, since we've time-averaged the data)
  • minsnr=3 : apply a minimum signal-to-noise cutoff. Solutions with less than this value will be flagged
  • gaintable=['calG192.gaincurve', 'calG192.requantizer', 'calG192.opacity'] : pre-apply the gaincurve, opacity, and requantizer caltables

Plot the phase solutions (using full phase range, -180 to 180, instead of autorange):

# In CASA
plotcal(caltable='calG192.G0', xaxis='time', yaxis='phase', \
        iteration='antenna', plotrange=[-1,-1,-180,180])

Step through the antenna-based solutions. They look good (and fairly flat over the scans).

NOTE: When you are done plotting and want to use the caltable in another task, use the Quit button on the GUI to dismiss the plotter and free up the lock on the caltable. You should see a message in your terminal window saying "Resetting plotcal" which means you are good to go!

If you want to make single-page multipanel plots (like those shown to the right), particularly for a hardcopy (where it only shows the first page), you can do:

# In CASA
plotcal(caltable='calG192.G0', xaxis='time', yaxis='phase', \
        antenna='0~10,12~15', subplot=531, iteration='antenna', \
        plotrange=[-1,-1,-180,180], fontsize=8.0, \
        markersize=3.0, figfile='plotG192_plotcal_G0p1.png')
plotcal(caltable='calG192.G0', xaxis='time', yaxis='phase', \
        antenna='16~26', subplot=531, iteration='antenna', \
        plotrange=[-1,-1,-180,180], fontsize=8.0, \
        markersize=3.0, figfile='plotG192_plotcal_G0p2.png')

We can now solve for the residual antenna-based delays that we saw in phase vs. frequency. This uses the gaintype='K' option in gaincal. Note that this currently does not do a "global fringe-fitting" solution for delays, but instead does a baseline-based delay solution for all baselines to the reference antenna, treating these as antenna-based delays. In most cases with high-enough S/N to get baseline-based delay solutions this will suffice. We avoid the edge channels of each spectral window by selecting channels 5~122:

# In CASA
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.K0', \
        gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                   'calG192.G0', 'calG192.opacity'], \
        field='3', spw='*:5~122', gaintype='K', \
        refant='ea05', solint='inf', minsnr=3)

Note that we have also pre-applied our initial phase table. We can plot the delays, in nanoseconds, as a function of antenna index (you will get one for each subband and polarization):

# In CASA
plotcal(caltable='calG192.K0', xaxis='antenna', yaxis='delay')

The delays range from around -5 to 4 nanoseconds.

Now we solve for the antenna bandpasses using the previous tables:

# In CASA
bandpass(vis='G192_flagged_6s.ms', caltable='calG192.B0', \
         gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                    'calG192.G0', 'calG192.K0', 'calG192.opacity'], \
         field='3', refant='ea05', solnorm=False, \
         bandtype='B', solint='inf', gaincurve=False)

WARNING: You must set solnorm=False here or later on you will find some offsets between spw due to how amplitude scaling adjusts weights internally during solving.

plotcal B0 bandpass phase ant ea06 spw 0-31
plotcal B0 bandpass phase ant ea06 spw 32-63

You will see in the terminal some reports of solutions failing due to "Insufficient unflagged antennas" -- note that these are for the channels we flagged earlier.

This is the first amplitude-scaling calibration that we do, so it is important to have used the calG192.gaincurve caltable (or set gaincurve=True) as well as the calG192.opacity caltable (or set opacity appropriately).

Plot the resulting bandpasses in amplitude and phase:

# In CASA
plotcal(caltable='calG192.B0', xaxis='freq', yaxis='amp', \
        spw='0~31', iteration='antenna')
#
plotcal(caltable='calG192.B0', xaxis='freq', yaxis='amp', \
        spw='32~63', iteration='antenna')
#
plotcal(caltable='calG192.B0', xaxis='freq', yaxis='phase', \
        iteration='antenna', spw='0~31', \
        plotrange=[-1,-1,-180,180])
#
plotcal(caltable='calG192.B0', xaxis='freq', yaxis='phase', \
        iteration='antenna', spw='32~63', \
        plotrange=[-1,-1,-180,180])

In the bandpass phase you no longer see the residual antenna delays (just residual spw phase offsets from the delay solution registration), but there are some band edge effects apparent.

Bootstrapping the bandpass calibrator spectrum

Unfortunately, our flux density calibrator was not bright enough at Ka-band to use as the bandpass calibration source. Since there is no a priori spectral information for our chosen bandpass calibrator, 3C84, we need to bootstrap to find its spectral index, then recalibrate with this information in order to avoid folding the intrinsic spectral shape of 3C84 into our calibration.

First, we use the initial round of bandpass calibration to create gain solutions for the flux and bandpass calibrators:

# In CASA
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1', field='0,3', \
        gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                   'calG192.opacity', 'calG192.K0', \
                   'calG192.B0'], \
        gaintype='G', refant='ea05', calmode='ap', solint='30s', minsnr=3)

Have a look at the phase and amplitude solutions, stepping through antenna. We look at the sources individually since they're fairly widely separated in time:

# In CASA
plotcal(caltable='calG192.G1', xaxis='time', yaxis='amp', \
        field='0', iteration='antenna')
#
plotcal(caltable='calG192.G1', xaxis='time', yaxis='amp', \
        field='3', iteration='antenna')
#
plotcal(caltable='calG192.G1', xaxis='time', yaxis='phase', \
        iteration='antenna', plotrange=[-1,-1,-180,180], \
        field='0')
#
plotcal(caltable='calG192.G1', xaxis='time', yaxis='phase', \
        iteration='antenna', plotrange=[-1,-1,-180,180], \
        field='3')

The solutions all look reasonable and relatively constant with time.

Now that we have gain solutions for the flux and bandpass calibrators, we can use fluxscale to scale the gain amplitudes of the bandpass calibrator:

# In CASA
flux1 = fluxscale(vis='G192_flagged_6s.ms', caltable='calG192.G1', \
                  fluxtable='calG192.F1', reference='0', \
                  transfer='3', listfile='3C84.fluxinfo', fitorder=1)
  • flux1 = ...: by providing a variable flux1, we allow fluxscale to use this for the output dictionary it returns with lots of information about the flux scaling.
  • fluxtable='calG192.F1': this is the output scaled gain table. Since we are only using this to find the spectral index of 3C84, we won't be using this table.
  • listfile='3C84.fluxinfo': an output file that contains the derived flux values and fit information.
  • fitorder=1: only find a spectral index, ignoring curvature in the spectrum.

The last line in the file (and displayed in the logger) shows:

# Fitted spectrum for 3c84-J0319+413 with fitorder=1: Flux density = 29.8756 +/- 0.0381046 (freq=32.4488 GHz) spidx=-0.598929 +/- 0.0105201
plotms of model amp vs freq for 3C84
3C84 flux values returned by fluxscale

Using the information in the returned flux dictionary, we can plot the derived spectrum:

# In CASA
freq = flux1['freq'] / 1e9
srcFlux = flux1['3']['fluxd']
srcErr = flux1['3']['fluxdErr']
pl.clf()
pl.plot(freq, srcFlux, 'bo')
pl.show()

Note the bump around 37 GHz -- what is this? We will not be able to account for it with the simple spectral index model, but still, ours is a good first approximation.

We can use the model from fluxscale to fill the MODEL column with 3C84's spectral information using setjy:

# In CASA
setjy(vis='G192_flagged_6s.ms', field='3', scalebychan=True, \
      fluxdensity=[29.8756, 0, 0, 0], spix=-0.598929, \
      reffreq='32.4488GHz')

Checking with plotms that the data have been appropriately filled:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='3', antenna='ea05&ea02', \
       xaxis='freq', yaxis='amp', ydatacolumn='model')
plotcal B0 bootstrapped bandpass amp ant ea06 spw 0-31
plotcal B0 bootstrapped bandpass amp ant ea06 spw 32-63
plotcal B0 bootstrapped bandpass phase ant ea06 spw 0-31
plotcal B0 bootstrapped bandpass phase ant ea06 spw 32-63

Finally, we redo the previous calibration using this new model information. Although the commands are the same as what we issued earlier, keep in mind that the model values for the bandpass calibrator have changed, and therefore the results of these calibration calculations will differ:

# In CASA
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G0.b', \
        field='3', spw='*:60~68', \
        gaintable=['calG192.gaincurve', \
                   'calG192.requantizer', 'calG192.opacity'], \
        gaintype='G', refant='ea05', calmode='p', \
        solint='int', minsnr=3) 
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.K0.b', \
        gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                   'calG192.G0.b', 'calG192.opacity'], \
        field='3', spw='*:5~122', gaintype='K', \
        refant='ea05', solint='inf', minsnr=3)
#
bandpass(vis='G192_flagged_6s.ms', caltable='calG192.B0.b', \
         gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                    'calG192.G0.b', 'calG192.K0.b', \
                    'calG192.opacity'], \
         field='3', refant='ea05', solnorm=False, \
         bandtype='B', solint='inf')

It's a good idea to inspect these solutions as well:

# In CASA
plotcal(caltable='calG192.B0.b', xaxis='freq', yaxis='amp', \
        spw='0~31', iteration='antenna')
#
plotcal(caltable='calG192.B0.b', xaxis='freq', yaxis='amp', \
        spw='32~63', iteration='antenna')
#
plotcal(caltable='calG192.B0.b', xaxis='freq', yaxis='phase', \
        iteration='antenna', spw='0~31', \
        plotrange=[-1,-1,-180,180])
#
plotcal(caltable='calG192.B0.b', xaxis='freq', yaxis='phase', \
        iteration='antenna', spw='32~63', \
        plotrange=[-1,-1,-180,180])

They look virtually unchanged from the previous solutions, with the exception that the amplitude scaling is corrected for the spectrum of 3C84. Now that we have the final version of our bandpass calibration, we can proceed to the full calibration of the dataset.

Final phase and amplitude calibration

plotcal G1.int per-int phase ea06
plotcal G1.inf per-scan phase ea06

Now we will compute calibrators' gain phases using the full bandwidth. We will do the calibrators one at a time and append subsequent solutions, since we will use different solution intervals. For 3C147 and 3C84, we obtain one solution per integration (these are bright enough); for J0603+174, we will use 12 s solution intervals:

# In CASA
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1.int', \
        gaintable=['calG192.requantizer','calG192.gaincurve', \
                   'calG192.opacity', \
                   'calG192.K0.b','calG192.B0.b'], \
        field='0', refant='ea05', solnorm=F, \
        solint='int', gaintype='G', calmode='p')
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1.int', \
        gaintable=['calG192.requantizer','calG192.gaincurve', \
                   'calG192.opacity', \
                   'calG192.K0.b','calG192.B0.b'], \
        field='1', refant='ea05', solnorm=F, \
        solint='12s', gaintype='G', calmode='p', \
        append=True)
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1.int', \
        gaintable=['calG192.requantizer','calG192.gaincurve', \
                   'calG192.opacity', \
                   'calG192.K0.b','calG192.B0.b'], \
        field='3', refant='ea05', solnorm=F, \
        solint='int', gaintype='G', calmode='p', \
        append=True)

These will get applied when solving for amplitudes, and when calibrating the calibrators themselves.

The phases track nicely with time:

# In CASA
plotcal(caltable='calG192.G1.int', xaxis='time', yaxis='phase', \
        iteration='antenna', plotrange=[-1,-1,-180,180])

To apply phase calibration to the target, we make a second table for the gain calibrator (J0603+174) with one solution per scan:

# In CASA
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1.inf', \
        gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                   'calG192.opacity', \
                   'calG192.K0.b', 'calG192.B0.b'], \
        field='1', refant='ea05', solnorm=F, \
        solint='inf', gaintype='G', calmode='p')

These scan phases will get interpolated by applycal onto our target. These look good as well:

# In CASA
plotcal(caltable='calG192.G1.inf', xaxis='time', yaxis='phase', \
        iteration='antenna', plotrange=[-1,-1,-180,180])

Now solve for amplitudes on a per scan interval, after applying the per-integration phases. Do these separately using gainfield so phases don't get transferred across fields. Note that gaincal uses linear interpolation of the previously determined phases by default, so set this to "nearest" if you want to override.

# In CASA
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G2', \
        gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                   'calG192.opacity', 'calG192.K0.b', \
                   'calG192.B0.b', 'calG192.G1.int'], \
        gainfield=['', '', '', '3', '3', '0'], \
        interp=['', '', '', 'nearest', 'nearest', 'nearest'], \
        field='0', refant='ea05', solnorm=F, \
        solint='inf', gaintype='G', calmode='a')
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G2', \
        gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                   'calG192.opacity', 'calG192.K0.b', \
                   'calG192.B0.b', 'calG192.G1.int'], \
        gainfield=['', '', '', '3', '3', '1'], \
        interp=['', '', '', 'nearest', 'nearest', 'nearest'], \
        field='1', refant='ea05', solnorm=F, \
        solint='inf', gaintype='G', calmode='a', append=True)
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G2', \
        gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                   'calG192.opacity', 'calG192.K0.b', \
                   'calG192.B0.b', 'calG192.G1.int'], \
        gainfield=['', '', '', '3', '3', '3'], \
        interp=['', '', '', 'nearest', 'nearest', 'nearest'], \
        field='3', refant='ea05', solnorm=F, \
        solint='inf', gaintype='G', calmode='a', append=True)
#
plotcal G2 per-scan amp ant ea06

Have a look at the amplitudes:

# In CASA
plotcal(caltable='calG192.G2', xaxis='time', yaxis='amp', \
        iteration='antenna')

This is the table we will apply to the data.

Now, we need to use fluxscale to transfer the amplitude gains from 3C147:

# In CASA
flux2 = fluxscale(vis='G192_flagged_6s.ms', caltable='calG192.G2', \
                  fluxtable='calG192.F2', reference='0')

where we have now captured the returned dictionary in the Python variable flux2.

The logger output gives:

Found reference field(s): 3C147
Found transfer field(s):  gcal-J0603+174 3c84-J0319+413
Flux density for gcal-J0603+174 in SpW=0 is: 0.252043 +/- 0.00779693 (SNR = 32.3259, N = 44)
Flux density for gcal-J0603+174 in SpW=1 is: 0.250608 +/- 0.00785259 (SNR = 31.9141, N = 44)
Flux density for gcal-J0603+174 in SpW=2 is: 0.250149 +/- 0.00783195 (SNR = 31.9395, N = 44)
Flux density for gcal-J0603+174 in SpW=3 is: 0.249326 +/- 0.00870076 (SNR = 28.6556, N = 44)
Flux density for gcal-J0603+174 in SpW=4 is: 0.24779 +/- 0.00860759 (SNR = 28.7873, N = 44)
<snip>
Flux density for gcal-J0603+174 in SpW=60 is: 0.280642 +/- 0.00884987 (SNR = 31.7115, N = 44)
Flux density for gcal-J0603+174 in SpW=61 is: 0.279742 +/- 0.00874457 (SNR = 31.9904, N = 44)
Flux density for gcal-J0603+174 in SpW=62 is: 0.278071 +/- 0.00910153 (SNR = 30.5521, N = 44)
Flux density for gcal-J0603+174 in SpW=63 is: 0.277588 +/- 0.00955455 (SNR = 29.0529, N = 44)
Flux density for 3c84-J0319+413 in SpW=0 is: 1.01141 +/- 0.0316725 (SNR = 31.9333, N = 44)
Flux density for 3c84-J0319+413 in SpW=1 is: 0.994812 +/- 0.0326974 (SNR = 30.4248, N = 44)
Flux density for 3c84-J0319+413 in SpW=2 is: 1.00473 +/- 0.0314246 (SNR = 31.9729, N = 44)
Flux density for 3c84-J0319+413 in SpW=3 is: 1.0042 +/- 0.0325531 (SNR = 30.8479, N = 44)
<snip>
Flux density for 3c84-J0319+413 in SpW=60 is: 1.00232 +/- 0.0243617 (SNR = 41.1434, N = 44)
Flux density for 3c84-J0319+413 in SpW=61 is: 1.00589 +/- 0.0248197 (SNR = 40.5277, N = 44)
Flux density for 3c84-J0319+413 in SpW=62 is: 1.01762 +/- 0.0240088 (SNR = 42.3855, N = 44)
Flux density for 3c84-J0319+413 in SpW=63 is: 1.01145 +/- 0.0249814 (SNR = 40.488, N = 44)
Fitted spectrum for gcal-J0603+174 with fitorder=1: Flux density = 0.264382 +/- 0.000149793 (freq=32.4488 GHz) spidx=-0.834342 +/- 0.00458913
Fitted spectrum for 3c84-J0319+413 with fitorder=1: Flux density = 1.00101 +/- 0.00121263 (freq=32.4488 GHz) spidx=0.00866148 +/- 0.0100409
Storing result in calG192.F2
Writing solutions to table: calG192.F2

You may see slightly different numbers on your machine. Note that "N" here is the number of antennas x the number of polarizations used for the calculations; in this case, there are 22 unflagged antennas and 2 polarizations.

Also, note that the flux-scaled amplitudes for 3C84 are all almost exactly 1 Jy. This is not because the actual flux of 3C84 is 1 Jy, of course. Rather, remember that the spectrum and flux information is now included in the bandpass table. When we apply the calibration, in the next section, you will see that 3C84's flux does indeed come out as expected.

Applying the Calibration and Final Editing

Next we apply all our accumulated calibration tables to the flagged MS. We apply these to the calibration fields individually, using the appropriate gainfields and interpolation for each:

  • For 3C147 (field 0) we did per-integration phase solutions and a single scan amplitude, so use "linear" and "nearest" interpolation, respectively;
  • for the nearby gain calibrator (field 1) we did 12-s phase and per-scan amplitude solutions, for which we will use "linear" and "nearest" interpolation, respectively;
  • for G192 (field 2), we will calibrate with field 1, using the per-scan solutions and "linear" interpolation; and finally,
  • for the bandpass calibrator 3C84 (field 3), we did per-integration phase solutions and a single scan amplitude, so use "linear" and "nearest" interpolation respectively.
3C147 with calibration applied
3C147 with calibration applied, amp vs. baseline
# In CASA
applycal(vis='G192_flagged_6s.ms', field='0', \
         gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                    'calG192.opacity', 'calG192.K0.b', \
                    'calG192.B0.b', 'calG192.G1.int', \
                    'calG192.G2'], \
         gainfield=['', '', '', '', '', '0', '0'],
         interp=['', '', '', 'nearest', 'nearest', 'linear', \
                 'nearest'], calwt=False)
#
applycal(vis='G192_flagged_6s.ms', field='1', \
         gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                    'calG192.opacity', 'calG192.K0.b', \
                    'calG192.B0.b', 'calG192.G1.int', \
                    'calG192.F2'], \
         gainfield=['', '', '', '', '', '1', '1'],
         interp=['', '', '', 'nearest', 'nearest', 'linear', \
                 'nearest'], calwt=False)
#
applycal(vis='G192_flagged_6s.ms', field='2', \
         gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                    'calG192.opacity', 'calG192.K0.b', \
                    'calG192.B0.b', 'calG192.G1.inf', \
                    'calG192.F2'], \
         gainfield=['', '', '', '', '', '1', '1'],
         interp=['', '', '', 'nearest', 'nearest', 'linear', \
                 'linear'], calwt=False)
#
applycal(vis='G192_flagged_6s.ms', field='3', \
         gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                    'calG192.opacity', 'calG192.K0.b', \
                    'calG192.B0.b', 'calG192.G1.int', \
                    'calG192.F2'], \
         gainfield=['', '', '', '', '', '3', '3'],
         interp=['', '', '', 'nearest', 'nearest', 'linear', \
                 'nearest'], calwt=False)

Because we used usesratch=False in setjy, the CORRECTED_DATA scratch column will be created the first time you run applycal. This will take a few minutes to write, increasing the size of the MS to 30 GB, and will store the calibrated data.

We can examine the corrected data for 3C147, avoiding spectral window edges, and binning the data in time and frequency:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='0', \
       xaxis='frequency', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='baseline')

See figure above right. There is some suspicious data in the frequency range 38.15-38.26 GHz (spw 29). We can plot around this frequency range with respect to time, to see if it's isolated RFI or something we should flag from the whole dataset:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='0', \
       xaxis='time', yaxis='amp', \
       ydatacolumn='corrected', spw='29:5~122', \
       averagedata=True, avgchannel='16', \
       avgtime='', coloraxis='baseline')

Indeed, something looks wrong for the time interval 6:35:00-6:36:40 for this spectral window. Flag these data:

# In CASA
flagdata(vis='G192_flagged_6s.ms', field='0', \
         spw='29', timerange='6:35:00~6:36:40')

It's also instructive to plot the corrected amplitude as a function of baseline:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='0', \
       xaxis='baseline', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='antenna1')

Looks good now!

Next, we examine the corrected data for the gain calibrator, J0603+174, again avoiding spectral window edges. This time, we will bin the data even more in frequency, since it's a fainter source:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='1', \
       xaxis='frequency', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='32', \
       avgtime='6000s', coloraxis='baseline')

This generally looks quite good. Plot with respect to baseline as well:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='1', \
       xaxis='baseline', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='32', \
       avgtime='6000s', coloraxis='antenna1')

A few antennas look a little noisier, but nothing bad enough to flag for now.

Finally, we examine the corrected data for 3C84:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='3', \
       xaxis='frequency', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='baseline')

In general, it looks good, though there is one rather suspicious baseline dropping below the rest of the data. Box a few data points and use the "Locate" button to find that this is ea03&ea07. Plotting the same baseline for 3C147, we see that it doesn't look the best there either, so we will flag this baseline:

# In CASA
flagdata(vis='G192_flagged_6s.ms', antenna='ea03&ea07')

Now, let's plot amplitude vs. baseline:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='3', \
       xaxis='baseline', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='antenna1')

Looks good!

Finally, let's plot amplitude vs. phase:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='3', \
       xaxis='phase', yaxis='amp', \
       xdatacolumn='corrected', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='baseline')

There is less than 2 degrees of phase scatter, and a plot vs. frequency shows that this is mostly in the highest frequencies. We will keep all these data.

Recalibration

Since we flagged additional data, we will now go back and recalibrate:

# In CASA
# Clear the corrected data and model from header
clearcal('G192_flagged_6s.ms', addmodel=False)
#
setjy(vis='G192_flagged_6s.ms', field='0', scalebychan=True, \
      modimage='3C147_A.im')
#
setjy(vis='G192_flagged_6s.ms', field='3', scalebychan=True, \
      fluxdensity=[29.8756, 0, 0, 0], spix=-0.598929, \
      reffreq='32.4488GHz')
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G0.b.2', field='3', \
        spw='*:60~68', gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                                  'calG192.opacity'], \
        gaintype='G', refant='ea05', calmode='p', solint='int', minsnr=3) 
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.K0.b.2', \
        field='3', spw='*:5~122', gaintype='K', \
        gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                   'calG192.G0.b.2', 'calG192.opacity'], \
        refant='ea05', solint='inf', minsnr=3)
#
bandpass(vis='G192_flagged_6s.ms', caltable='calG192.B0.b.2', \
         field='3', refant='ea05', solnorm=False, \
         gaintable=['calG192.gaincurve', 'calG192.requantizer', \
                    'calG192.G0.b.2', 'calG192.K0.b.2', 'calG192.opacity'], \
         bandtype='B', solint='inf')
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1.int.2', \
        field='0', refant='ea05', solnorm=F, \
        gaintable=['calG192.requantizer','calG192.gaincurve', \
                   'calG192.opacity', \
                   'calG192.K0.b.2','calG192.B0.b.2'], \
        solint='int', gaintype='G', calmode='p')
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1.int.2', \
        field='1', refant='ea05', solnorm=F, \
        gaintable=['calG192.requantizer','calG192.gaincurve', \
                   'calG192.opacity', \
                   'calG192.K0.b.2','calG192.B0.b.2'], \
        solint='12s', gaintype='G', calmode='p', \
        append=True)
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1.int.2', \
        field='3', refant='ea05', solnorm=F, \
        gaintable=['calG192.requantizer','calG192.gaincurve', \
                   'calG192.opacity', \
                   'calG192.K0.b.2','calG192.B0.b.2'], \
        solint='int', gaintype='G', calmode='p', \
        append=True)
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G1.inf.2', \
        field='1', refant='ea05', solnorm=F, \
        gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                   'calG192.opacity', \
                   'calG192.K0.b.2', 'calG192.B0.b.2'], \
        solint='inf', gaintype='G', calmode='p')
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G2.2', \
        field='0', refant='ea05', solnorm=F, \
        gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                   'calG192.opacity', 'calG192.K0.b.2', \
                   'calG192.B0.b.2', 'calG192.G1.int.2'], \
        gainfield=['', '', '', '3', '3', '0'], \
        interp=['', '', '', 'nearest', 'nearest', 'nearest'], \
        solint='inf', gaintype='G', calmode='a')
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G2.2', \
        field='1', refant='ea05', solnorm=F, \
        gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                   'calG192.opacity', 'calG192.K0.b.2', \
                   'calG192.B0.b.2', 'calG192.G1.int.2'], \
        gainfield=['', '', '', '3', '3', '1'], \
        interp=['', '', '', 'nearest', 'nearest', 'nearest'], \
        solint='inf', gaintype='G', calmode='a', append=True)
#
gaincal(vis='G192_flagged_6s.ms', caltable='calG192.G2.2', \
        field='3', refant='ea05', solnorm=F, \
        gaintable=['calG192.requantizer', 'calG192.gaincurve', \
                   'calG192.opacity', 'calG192.K0.b.2', \
                   'calG192.B0.b.2', 'calG192.G1.int.2'], \
        gainfield=['', '', '', '3', '3', '3'], \
        interp=['', '', '', 'nearest', 'nearest', 'nearest'], \
        solint='inf', gaintype='G', calmode='a', append=True)
#
flux3 = fluxscale(vis='G192_flagged_6s.ms', caltable='calG192.G2.2', \
                  fluxtable='calG192.F2.2', reference='0')
#
applycal(vis='G192_flagged_6s.ms', field='0', \
         gaintable=['calG192.requantizer', 'calG192.gaincurve', 'calG192.opacity', 'calG192.K0.b.2', 'calG192.B0.b.2', 'calG192.G1.int.2', 'calG192.G2.2'], \
         gainfield=['', '', '', '', '', '0', '0'], \
         interp=['', '', '', 'nearest', 'nearest', 'linear', 'nearest'], calwt=False)
#
applycal(vis='G192_flagged_6s.ms', field='1', \
         gaintable=['calG192.requantizer', 'calG192.gaincurve', 'calG192.opacity', 'calG192.K0.b.2', 'calG192.B0.b.2', 'calG192.G1.int.2', 'calG192.F2.2'], \
         gainfield=['', '', '', '', '', '1', '1'], \
         interp=['', '', '', 'nearest', 'nearest', 'linear', 'nearest'], calwt=False)
#
applycal(vis='G192_flagged_6s.ms', field='2', \
         gaintable=['calG192.requantizer', 'calG192.gaincurve', 'calG192.opacity', 'calG192.K0.b.2', 'calG192.B0.b.2', 'calG192.G1.inf.2', 'calG192.F2.2'], \
         gainfield=['', '', '', '', '', '1', '1'], \
         interp=['', '', '', 'nearest', 'nearest', 'linear', 'linear'], calwt=False)
#
applycal(vis='G192_flagged_6s.ms', field='3', \
         gaintable=['calG192.requantizer', 'calG192.gaincurve', 'calG192.opacity', 'calG192.K0.b.2', 'calG192.B0.b.2', 'calG192.G1.int.2', 'calG192.F2.2'], \
         gainfield=['', '', '', '', '', '3', '3'], \
         interp=['', '', '', 'nearest', 'nearest', 'linear', 'nearest'], calwt=False)

The recalibration will take a little while -- it was over 1.5 hours on our system -- so this is a good time to work on a different project or grab some lunch!

The fluxscale output this time around is slightly different:

Found reference field(s): 3C147
Found transfer field(s):  gcal-J0603+174 3c84-J0319+413
Flux density for gcal-J0603+174 in SpW=0 is: 0.252049 +/- 0.00779748 (SNR = 32.3244, N = 44)
Flux density for gcal-J0603+174 in SpW=1 is: 0.250619 +/- 0.00784916 (SNR = 31.9294, N = 44)
Flux density for gcal-J0603+174 in SpW=2 is: 0.250149 +/- 0.00783732 (SNR = 31.9177, N = 44)
Flux density for gcal-J0603+174 in SpW=3 is: 0.249327 +/- 0.00869472 (SNR = 28.6757, N = 44)
Flux density for gcal-J0603+174 in SpW=4 is: 0.247794 +/- 0.00861206 (SNR = 28.7729, N = 44)
<snip>
Flux density for gcal-J0603+174 in SpW=60 is: 0.280654 +/- 0.00883115 (SNR = 31.78, N = 44)
Flux density for gcal-J0603+174 in SpW=61 is: 0.279748 +/- 0.00876293 (SNR = 31.924, N = 44)
Flux density for gcal-J0603+174 in SpW=62 is: 0.27807 +/- 0.00912204 (SNR = 30.4833, N = 44)
Flux density for gcal-J0603+174 in SpW=63 is: 0.277579 +/- 0.00954328 (SNR = 29.0863, N = 44)
Flux density for 3c84-J0319+413 in SpW=0 is: 1.01141 +/- 0.0316702 (SNR = 31.9356, N = 44)
Flux density for 3c84-J0319+413 in SpW=1 is: 0.994812 +/- 0.0326958 (SNR = 30.4262, N = 44)
Flux density for 3c84-J0319+413 in SpW=2 is: 1.00473 +/- 0.0314171 (SNR = 31.9805, N = 44)
Flux density for 3c84-J0319+413 in SpW=3 is: 1.00419 +/- 0.0325563 (SNR = 30.8449, N = 44)
Flux density for 3c84-J0319+413 in SpW=4 is: 1.00361 +/- 0.0333546 (SNR = 30.0893, N = 44)
<snip>
Flux density for 3c84-J0319+413 in SpW=60 is: 1.00232 +/- 0.0243542 (SNR = 41.156, N = 44)
Flux density for 3c84-J0319+413 in SpW=61 is: 1.00588 +/- 0.0248152 (SNR = 40.5347, N = 44)
Flux density for 3c84-J0319+413 in SpW=62 is: 1.01771 +/- 0.0239908 (SNR = 42.4207, N = 44)
Flux density for 3c84-J0319+413 in SpW=63 is: 1.01143 +/- 0.0249739 (SNR = 40.4996, N = 44)
Fitted spectrum for gcal-J0603+174 with fitorder=1: Flux density = 0.264388 +/- 0.000149708 (freq=32.4488 GHz) spidx=-0.834284 +/- 0.00458657
Fitted spectrum for 3c84-J0319+413 with fitorder=1: Flux density = 1.00109 +/- 0.00122518 (freq=32.4488 GHz) spidx=0.00940404 +/- 0.010148
3C147 with calibration applied, amp vs. phase
J0603+174 with calibration applied, amp vs. phase
3C84 with calibration applied, amp vs. phase

As always, it's a good idea to check the corrected data with plotms. Plots of corrected amplitude vs. baseline:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='0', \
       xaxis='baseline', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='antenna1')
#
plotms(vis='G192_flagged_6s.ms', field='1', \
       xaxis='baseline', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='32', \
       avgtime='6000s', coloraxis='antenna1')
#
plotms(vis='G192_flagged_6s.ms', field='3', \
       xaxis='baseline', yaxis='amp', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='antenna1')

And, finally, corrected amplitude vs. corrected phase:

# In CASA
plotms(vis='G192_flagged_6s.ms', field='0', \
       xaxis='phase', yaxis='amp', \
       xdatacolumn='corrected', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='baseline')
#
plotms(vis='G192_flagged_6s.ms', field='1', \
       xaxis='phase', yaxis='amp', \
       xdatacolumn='corrected', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='32', \
       avgtime='6000s', coloraxis='baseline')
#
plotms(vis='G192_flagged_6s.ms', field='3', \
       xaxis='phase', yaxis='amp', \
       xdatacolumn='corrected', \
       ydatacolumn='corrected', spw='*:5~122', \
       averagedata=True, avgchannel='8', \
       avgtime='1000s', coloraxis='baseline')

Everything looks good, and the recalibration made only minor adjustments since there wasn't very much additional flagged data.

Now split off the data for the calibrators and target field, so we can restore easily in case any issues corrupt the MSs. Also, first remove any existing split data, otherwise split will not work:

# In CASA
os.system('rm -rf 3C147_split_6s.ms')
split(vis='G192_flagged_6s.ms', outputvis='3C147_split_6s.ms', \
      datacolumn='corrected', field='0')
#
os.system('rm -rf J0603_split_6s.ms')
split(vis='G192_flagged_6s.ms', outputvis='J0603_split_6s.ms', \
      datacolumn='corrected', field='1')
#
os.system('rm -rf G192_split_6s.ms')
split(vis='G192_flagged_6s.ms', outputvis='G192_split_6s.ms', \
      datacolumn='corrected', field='2')
#
os.system('rm -rf 3C84_split_6s.ms')
split(vis='G192_flagged_6s.ms', outputvis='3C84_split_6s.ms', \
      datacolumn='corrected', field='3')

We can now move on to imaging.

Imaging

The G192 data were taken in the VLA's highest-resolution A-configuration at Ka-band. To determine the best parameters for imaging, it helps to start with the relevant information in the Observational Status Summary:

  • Synthesized beam is 0.059" at 33 GHz with a primary beam field of view of 1.4 arcmin (82")

Our data spans 27.0-38.4 GHz: this is a relatively large fractional bandwidth, resulting in substantial variation of the field of view over the entire frequency range. The FOV = 45 arcmin / Frequency (GHz), giving 1.7 arcmin at 27 GHz and 1.2 arcmin at 38.4 GHz. Likewise, the synthesized beam ranges from 0.072" at 27 GHz to 0.051" at 38.4 GHz. We want to subsample the synthesized beam by a factor of 3-4, so will use a cellsize of 0.015". To cover the full FOV, we would want a minimum image size of 6800 pixels. However, there isn't much outside the center of the field for G192 -- this is what gave us leeway to average to 6 seconds -- so, to save time, will will only image a 1280x1280 pixel field (19.2"x19.2").

We will also use the Briggs robust (with robust=0.5) weighting, which is a compromise between uniform and natural weighting, and will give reasonable resolution but will allow us to still see larger scale structure.

Due to the numerology of FFTW's (which clean uses under the hood for FFTs) optimal sizes, imsize should be an even number with prime factors chosen from 2, 3, 5, and 7. Since 1280 = (2^8)*5, it will give us optimal clean performance.

For more information on using clean, in particular on using the interactive GUI, see EVLA_Continuum_Tutorial_3C391#Imaging.

NOTE: If you are pressed for time, then you might want to jump ahead to cleaning both basebands, and while it is cleaning you can read the other Imaging descriptions.

Cleaning a single spectral window

Let us start by interactively cleaning one spectral window in the lower-frequency baseband (spw 48). (For Ka-band, the higher-numbered spectral-window baseband is actually the lower-frequency baseband.) NOTE: this first time will take a few minutes at start to create scratch columns in the MS in case we want to do self-calibration later.

Note that interrupting clean by Ctrl+C may corrupt your visibilities -- you may be better off choosing to let clean finish. We are working on a way to prevent this from happening, but for the moment it's best to avoid Ctrl+C.

viewer showing clean spw48 1280x1280 restored image
# In CASA
# Removing any previous cleaning information
# This assumes you want to start this clean from scratch
# If you want to continue this from a previous clean run, 
# the rm -rf system command should be be skipped
os.system ('rm -rf imgG192_6s_spw48*')
clean(vis='G192_split_6s.ms', spw='48:5~122', \
      imagename='imgG192_6s_spw48', \
      mode='mfs', nterms=1, niter=10000, \
      imsize=[1280], cell=['0.015arcsec'], \
      imagermode='csclean', cyclefactor=1.5, \
      weighting='briggs', robust=0.5, \
      interactive=True)
  • Click on the wrench icon ViewerWrench.png to bring up the Data Display Options, and change the color scale to "Hot Metal 1" under "basic settings"
  • Zoom in 3 times
  • Box the point-like source and clean for 50 iterations.
  • Stop cleaning when the residuals look like noise (this will probably happen after the first 50 iterations).
  • To stop, click the red Clean-stop.png button.

When clean is finished, we can look at the restored image:

# In CASA
viewer('imgG192_6s_spw48.image')

The restored image is shown above. It's a very good idea to stick with the Hot Metal 1 color scale throughout this Guide, since it does a better job of revealing faint emission than the default scheme.

Check the rms of the residuals using the imstat task:

# In CASA
mystat = imstat('imgG192_6s_spw48.residual')
print 'Residual standard deviation = '+str(mystat['sigma'][0])

In this particular case, it's 136 uJy; yours will likely be slightly different.

Cleaning the lower-frequency baseband

clean boxes spw32-63
clean spw32-63 restored image center

Here we will image the entire lower-frequency baseband (spw 32-63). Follow the same iterative procedure as before, and get the best residuals you can without "cleaning the noise".

# In CASA
# Removing any previous cleaning information
# This assumes you want to start this clean from scratch
# If you want to continue this from a previous clean run, 
# the rm -rf system command should be be skipped
os.system ('rm -rf imgG192_6s_spw32-63*')
clean(vis='G192_split_6s.ms', spw='32~63:5~122', \
      imagename='imgG192_6s_spw32-63', \
      mode='mfs', nterms=1, niter=10000, \
      imsize=[1280], cell=['0.015arcsec'], \
      imagermode='csclean', cyclefactor=1.5, \
      weighting='briggs', robust=0.5, \
      interactive=True)
#
viewer('imgG192_6s_spw32-63.image')
mystat = imstat('imgG192_6s_spw32-63.residual')
print 'Residual standard deviation = '+str(mystat['sigma'][0])
  • Because of the increased bandwidth, it is easier to see two fainter point sources.
  • Be careful cleaning sources that lie near or on sidelobe peaks.
  • Clean the central emission region first (50 iterations) to reduce the sidelobe level before adding any more components. The screenshot above shows the interactive clean window after 50 iterations with the three clean boxes we created.

For this run, the rms is 23 uJy. To the right is a zoom-in on the center of the restored image.

Finally, we will fit the central point source to determine its flux. First, create a box region around the source in the viewer, and save it as G192.crtf (View -> Regions -> File; see the screenshot below right). Note that you can drag the Regions window out of the main Viewer window if it's taking up too much space.

Use this region to fit the source flux:

# In CASA
myfit = imfit('imgG192_6s_spw32-63.image', region='G192.crtf')
print 'Source flux = '+str(myfit['results']['component0']['flux']['value'][0])+'+/-'+str(myfit['results']['component0']['flux']['error'][0])
saving CASA region for G192

The derived flux is 2.64 +/- 0.04 mJy. Also, have a look at the logger output:

Image component size (convolved with beam) ---
       --- major axis FWHM:     80.01 +/- 0.98 marcsec
       --- minor axis FWHM:     71.51 +/- 1.01 marcsec
       --- position angle: 63.2 +/- 2.2 deg
   
Clean beam size ---
       --- major axis FWHM: 0.06 arcsec
       --- minor axis FWHM: 0.06 arcsec
       --- position angle: 29.00 deg
Image component size (deconvolved from beam) ---
       --- major axis FWHM:     51.3 +/- 1.8 marcsec
       --- minor axis FWHM:     37.7 +/- 2.3 marcsec
       --- position angle: 78.5 +/- 6.3 deg

Although it appears point-like, G192 is actually resolved! The deconvolved size of around 45 milliarcseconds corresponds to a size of 90 AU (assuming a distance of approximately 2 kpc). Indeed, this is thought to be the accretion disk around the protostar! (See this article for the initial report, using 43 GHz data, of the accretion disk around G192.)

Cleaning the upper-frequency baseband

clean spw32-63 restored image center

Now we will image the entire upper-frequency baseband (spw 0-31). Follow the same iterative procedure as before, and get the best residuals you can without "cleaning the noise".

# In CASA
# Removing any previous cleaning information
# This assumes you want to start this clean from scratch
# If you want to continue this from a previous clean run, 
# the rm -rf system command should be be skipped
os.system ('rm -rf imgG192_6s_spw0-31*')
clean(vis='G192_split_6s.ms', spw='0~31:5~122', \
      imagename='imgG192_6s_spw0-31', \
      mode='mfs', nterms=1, niter=10000, \
      imsize=[1280], cell=['0.015arcsec'], \
      imagermode='csclean', cyclefactor=1.5, \
      weighting='briggs', robust=0.5, \
      interactive=True)
#
viewer('imgG192_6s_spw0-31.image')
mystat = imstat('imgG192_6s_spw0-31.residual')
print 'Residual standard deviation = '+str(mystat['sigma'][0])
myfit = imfit('imgG192_6s_spw0-31.image', region='G192.crtf')
print 'Source flux = '+str(myfit['results']['component0']['flux']['value'][0])+'+/-'+str(myfit['results']['component0']['flux']['error'][0])

For this run, the rms is 31 uJy, and the source flux is 3.07 +/- 0.06 mJy. Again, imfit finds that the source is extended. To the right is a zoom-in on the center of the restored image.

Cleaning both basebands using two MFS Taylor terms

From the individual images of the upper- and lower-frequency basebands, we can see that the source spectrum of G192 is relatively flat, with a spectral index of approximately


\alpha = \log(S_1 / S_2) / \log(\nu_1 / \nu_2) 

 = \log(3.07 / 2.64) / \log(36.5 / 29.0) 

 = 0.66,

where the convention for the spectral index alpha is that


S \propto \nu^\alpha.

Within a single baseband, neglecting to account for the spectral index will make little difference -- however, when we combine the two basebands, it is best to account for the spectral variation across the total band. For this, we will set nterms=2 in clean.

This option creates two "Taylor term" images -- an average intensity image (with suffix .image.tt0), and a spectral slope image (with suffix .image.tt1), which is intensity x alpha (where alpha is the spectral index). For convenience, there is also a spectral index image (with suffix .image.alpha). These Taylor expansions are with respect to the "reference frequency" of the image (by default the center frequency of the selected spectral window, but can be specified using the reffreq parameter in clean).

We will clean the complete dataset using nterms=2 Note: if you're feeling a bit lazy, and trust your previous set of clean boxes, you can also set mask='imgG192_6s_spw0-31.mask' or mask='imgG192_6s_spw32-63.mask' to use these as a starting point rather than running an interactive clean session. In this case, you should modify the threshold and niter parameters to avoid over-cleaning.

# In CASA
# Removing any previous cleaning information
# This assumes you want to start this clean from scratch
# If you want to continue this from a previous clean run, 
# the rm -rf system command should be be skipped
os.system ('rm -rf imgG192_6s_spw0-63_mfs2*')
clean(vis='G192_split_6s.ms', spw='0~63:5~122', \
      imagename='imgG192_6s_spw0-63_mfs2', \
      mode='mfs', nterms=2, niter=10000, gain=0.1, \
      threshold='0.0mJy', psfmode='clark', imsize=[1280], \
      cell=['0.015arcsec'], \
      weighting='briggs', robust=0.5, interactive=True)
#
mystat = imstat('imgG192_6s_spw0-63_mfs2.residual.tt0')
print 'Residual standard deviation = '+str(mystat['sigma'][0])
myfit = imfit('imgG192_6s_spw0-63_mfs2.image.tt0', region='G192.crtf')
print 'Source flux = '+str(myfit['results']['component0']['flux']['value'][0])+'+/-'+str(myfit['results']['component0']['flux']['error'][0])

For this run, the rms is 19.7 uJy, and the peak of the emission from G192 is 1.8 mJy, and the integrated source flux is 2.86 +/- 0.04 mJy (as before, the source is found to be extended). You can use the viewer to load the average intensity image:

# In CASA
viewer('imgG192_6s_spw0-63_mfs2.image.tt0')
clean spw0-63 mfs nterms=2 load alpha with LEL

Since the spectral index image is very noisy in the lower-intensity regions, we will use immath task to filter the spectral index image explicitly, using a Lattice Expression Language (LEL) expression:

# In CASA
immath(imagename=['imgG192_6s_spw0-63_mfs2.image.alpha', 
                  'imgG192_6s_spw0-63_mfs2.image.tt0'],
       mode='evalexpr',
       expr='IM0[IM1>2.0E-4]',
       outfile='imgG192_6s_spw0-63_mfs2.image.alpha.filtered')

This will use 0.2 mJy (10 x the rms) as the cutoff. You can then view or manipulate the filtered alpha image as usual.

We can also use LEL to filter the alpha image on intensity on-the-fly when we load the raster via the Open Data panel, by specifying a LEL string in the LEL box instead of selecting the image from the directory listing. The LEL string

'imgG192_6s_spw0-63_mfs2.image.alpha'['imgG192_6s_spw0-63_mfs2.image.tt0'>2E-04]

will replicate what we did above. The middle figure to the right shows the Open Data panel with our LEL string in it. Just click the Raster button to load this.

clean spw0-63 mfs nterms=2 tt0 and alpha (filtered at 0.2 mJy in tt0)
clean spw0-63 mfs nterms=2 alpha and alpha error (filtered at 0.2 mJy in tt0)

The lower panel to the right shows the intensity and LEL-filtered alpha images side-by-side in the viewer, zoomed in on the brightest source of emission. Creating a box around this region and double-clicking reveals that the spectral index varies from around -0.33 to 1.4, with the pixels in the brightest portion of the image at around 0.8, similar to what we found by hand using the information from the single-baseband images.

To get a sense of the probable errors for this spectral index information, we perform a similar filtering operation on the imgG192_6s_spw0-63_mfs2.image.alpha.error>/tt> image:

# In CASA
immath(imagename=['imgG192_6s_spw0-63_mfs2.image.alpha.error', 
                  'imgG192_6s_spw0-63_mfs2.image.tt0'],
       mode='evalexpr',
       expr='IM0[IM1>2E-4]',
       outfile='imgG192_6s_spw0-63_mfs2.image.alpha.error.filtered')

Now, we can load both the <tt>alpha and alpha.error images side-by-side in the viewer:

# In CASA
viewer('imgG192_6s_spw0-63_mfs2.image.alpha.filtered')

As one might expect, the errors are higher outside the emission peak (see the screenshot on the right). However, it seems possible that the .error image is underestimating the true errors on the mfs-calculated spectral index, since the central brightest pixels only have errors of around 0.15, when we calculated an alpha of 0.66 (compared with the mfs-calculated alpha of 0.8). If we were planning to use the reported spectral index information for publication, we would need to go through a more thorough investigation of the actual error analysis and spectral index.

Analyzing the image

From imstat on the final combined-baseband image, we got an image rms of 19.7 uJy. A reasonable question to ask is what we would expect the image rms to be: one way to estimate this is to determine the effective on-source time, then input the appropriate parameters to the VLA exposure calculator to determine the expected rms.

# In CASA
listobs('G192_split_6s.ms', listunfl=True)

This will show:

ID   Code Name                RA               Decl           Epoch   SrcId      nRows    nUnflRows
0    NONE G192.16-3.84        05:58:13.540000 +16.31.58.30001 J2000   0        2931890   2901697.32

Note that the "nUnflRows," or number of unflagged rows, is 2901697.32. Every row is a single baseline-integration-spw record, as you probably learned if you looked at the MS with browsetable. So, to use this to calculate an "effective" exposure time for the VLA Exposure Calculator for 22 antennas (22*21/2 = 231 baselines), we find that time = 2901697.32 * 6 seconds / 231 baselines / 64 spectral windows = 1178 seconds = 19.6 minutes. Our effective bandwidth is 7552 MHz, taking into account the spectral window selection. Using the median frequency of 32.7 GHz, the VLA exposure calculator reports that we should achieve an image rms of 13.5 uJy. Although our actual rms is somewhat higher, this is not unexpected; we have not done any self-calibration, for example.

Next, we will do some rough analysis on the spectral index to determine an intensity-weighted mean spectral index for G192. The .image.tt1 from our mfs is an intensity times alpha image (see the figure to the right). Let's filter this Taylor-term image by intensity as we did with the .alpha image:

# In CASA
# Removing any file output from previous runs, so immath will proceed
os.system('rm -rf imgG192_6s_spw0-63_mfs2.image.tt1.filtered')
immath(imagename=['imgG192_6s_spw0-63_mfs2.image.tt1',
                  'imgG192_6s_spw0-63_mfs2.image.tt0'],
       mode='evalexpr',
       expr='IM0[IM1>2E-4]',
       outfile='imgG192_6s_spw0-63_mfs2.image.tt1.filtered')
#
# Removing any file output from previous runs, so immath will proceed
os.system('rm -rf imgG192_6s_spw0-63_mfs2.image.tt0.filtered')
immath(imagename=['imgG192_6s_spw0-63_mfs2.image.tt0'],
       mode='evalexpr',
       expr='IM0[IM0>2E-4]',
       outfile='imgG192_6s_spw0-63_mfs2.image.tt0.filtered')

We can use the same region we created for imstat. Let us compute the intensity-weighted spectral index over this region by averaging these masked images using imstat and computing the ratio:

# In CASA
mystat = imstat('imgG192_6s_spw0-63_mfs2.image.tt1.filtered',
                region='G192.crtf')
avgtt0alpha = mystat['mean'][0]
#
mystat = imstat('imgG192_6s_spw0-63_mfs2.image.tt0.filtered',
                region='G192.crtf')
avgtt0 = mystat['mean'][0]
avgalpha = avgtt0alpha / avgtt0
print 'G192 intensity-weighted alpha = ' + str(avgalpha)

We get:

G192 intensity-weighted alpha = 0.737300481129

This is pretty close to the value we found from the single-baseband images of alpha = 0.66, validating the results from mfs with nterms=2.

What to do next: some exercises for the user

Here are a number of things you can try after completing this tutorial:

  1. Use self-calibration to improve the data and re-clean to make a better image. See this tutorial for more information on self-calibration.
  2. Investigate the data further to see if any more flagging is needed.
  3. Image the calibrators. What sort of dynamic range can you get on them? Is self-calibration needed (and if so what dynamic range do you get when you use it)?
  4. Try the testautoflag task (in 3.3.0 and later) to automatically flag bad data (though there is not much left, really). There is more information on running testautoflag in this tutorial.

Credits

The Jansky Very Large Array (VLA) is a partnership of the United States, Canada, and Mexico. The VLA is funded in the United States by the National Science Foundation, in Canada by the National Research Council, and in Mexico by the Comisión Nacional de Investigación Científica y Tecnológica (CONICyT).

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Last checked on CASA Version 4.1.0.