VLBA AIPS-to-CASA Primer: Difference between revisions

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The primer (or "cheat sheet") is intended to help those VLBA users who are used to calibrating and imaging their data in AIPS transition to CASA.
This primer (or "cheat sheet") is intended to help those VLBA users who are used to calibrating and imaging their data in AIPS transition to CASA.


It presents the AIPS VLBAUTIL procedures, the AIPS task(s) associated with those procedures, and the equivalent CASA task(s) and/or tool(s).
== VLBAUTIL Procedures ==
This section presents the AIPS VLBAUTIL procedures, the AIPS task(s) associated with those procedures, and the equivalent CASA task(s) and/or tool(s).


== Loading Data ==
=== Loading Data ===


Both AIPS and CASA need to take the FITS-IDI file and convert it into a format they can use.  AIPS uses the UVDATA format, and CASA uses the Measurement Set (MS) format.
Both AIPS and CASA need to take the FITS-IDI file and convert it into a format they can use.  AIPS uses the UVDATA format, and CASA uses the Measurement Set (MS) format.
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== Observation Summary ==
=== Observation Summary ===


Printing a summary of the observation is often useful for identifying the fringe finder, bandpass calibrator, phase reference calibrator, and science target.  It is also useful for locating a good time range to use for the instrumental delay correction.
Printing a summary of the observation is often useful for identifying the fringe finder, bandpass calibrator, phase reference calibrator, and science target.  It is also useful for locating a good time range to use for the instrumental delay correction.
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! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
|-
|VLBASUMM || LISTR<br/>optype 'scan' || listobs
|rowspan="2"| VLBASUMM  
|PRTAN
|rowspan="2"| listobs
|-
|LISTR<br/>optype 'scan'
|}
 
 
=== Total Electron Content Correction ===
 
 
{| class="wikitable"
|-
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
| VLBATECR || TECOR || no equivalent CASA task yet
|}
 
<b>NOTE: </b>Do not use the tec_maps tool with VLBA data.  It does not work properly for VLBI observations.
 
 
== Earth Orientation Parameter Correction ==
 
 
{| class="wikitable"
|-
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
| VLBAEOPS || CLCOR<br/>opcode 'eops' || no equivalent CASA task yet
|}
 
 
=== Sampler Corrections ===
 
 
{| class="wikitable"
|-
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
|rowspan="3"| VLBACCOR
| ACCOR
| accor
|-
| SNSMO
| smoothcal
|-
| CLCAL
| applycal
|}
 
=== Instrumental Delay Correction ===
 
<b>NOTE: </b>Many VLBA users are likely familiar with the VLBAUTIL procedure VLBAPCOR and the associated AIPS task PCCOR, which use the pulse-cal tone information from the VLBA to correct for the instrumental delay.  CASA does not currently have a means of working with the pulse-cal tones, so it cannot use this functionality.  It is an area of active development for the NRAO and JIVE CASA software engineers and scientists.
 
{| class="wikitable"
|-
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
|rowspan="2"| VLBAMPCL
| FRING
| fringefit
|-
| CLCAL
| applycal
|}
 
 
=== Global Fringe Fitting ===
 
The VLBAUTIL package contains 2 methods for doing the global fringe fit:
* VLBAFRNG does a fringe fit on every source in the observation
* VLBAFRGP does a fringe fit on the phase-reference calibrator(s) and transfers those solutions to the science target(s)
 
{| class="wikitable"
|-
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
|rowspan="2"| VLBAFRNG<br/>or VLBAFRGP
| FRING
| fringefit
|-
| CLCAL
| applycal
|}
 
 
=== Bandpass Correction ===
 
{| class="wikitable"
|-
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
| VLBABPSS || BPASS || bandpass
|}
 
 
=== Final Amplitude Calibration ===
 
{| class="wikitable"
|-
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
|rowspan="5"| VLBAAMP
| ACSCL
| accor
|-
| SNSMO
| smoothcal
|-
| CLCAL
| applycal
|-
| APCAL
| gencal
|-
| CLCAL
| applycal
|}
 
=== Parallactic Angle Correction ===
 
{| class="wikitable"
|-
! VLBAUTIL Procedure !! AIPS Task(s) !! CASA Task(s)
|-
| VLBAPANG || CLCOR<br/>opcode 'pang' || set parang=True in applycal, fringefit, and bandpass
|}
 
== Additional Tasks ==
 
{| class="wikitable"
|-
! AIPS Task !! CASA Task
|-
| SPLIT || split
|-
| IMAGR || tclean
|-
| CALIB || gaincal
|-
| POSSM || plotms
|-
| SNPLT || plotms
|-
| UVPLT || plotms
|-
| UVFLG || flagadata
|-
| FITTP || exportuvfits or exportfits
|}
|}

Latest revision as of 22:38, 2 November 2022

This primer (or "cheat sheet") is intended to help those VLBA users who are used to calibrating and imaging their data in AIPS transition to CASA.

VLBAUTIL Procedures

This section presents the AIPS VLBAUTIL procedures, the AIPS task(s) associated with those procedures, and the equivalent CASA task(s) and/or tool(s).

Loading Data

Both AIPS and CASA need to take the FITS-IDI file and convert it into a format they can use. AIPS uses the UVDATA format, and CASA uses the Measurement Set (MS) format.

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBALOAD FITLD importfitsidi


Observation Summary

Printing a summary of the observation is often useful for identifying the fringe finder, bandpass calibrator, phase reference calibrator, and science target. It is also useful for locating a good time range to use for the instrumental delay correction.

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBASUMM PRTAN listobs
LISTR
optype 'scan'


Total Electron Content Correction

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBATECR TECOR no equivalent CASA task yet

NOTE: Do not use the tec_maps tool with VLBA data. It does not work properly for VLBI observations.


Earth Orientation Parameter Correction

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBAEOPS CLCOR
opcode 'eops'		 no equivalent CASA task yet


Sampler Corrections

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBACCOR ACCOR accor
SNSMO smoothcal
CLCAL applycal

Instrumental Delay Correction

NOTE: Many VLBA users are likely familiar with the VLBAUTIL procedure VLBAPCOR and the associated AIPS task PCCOR, which use the pulse-cal tone information from the VLBA to correct for the instrumental delay. CASA does not currently have a means of working with the pulse-cal tones, so it cannot use this functionality. It is an area of active development for the NRAO and JIVE CASA software engineers and scientists.

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBAMPCL FRING fringefit
CLCAL applycal


Global Fringe Fitting

The VLBAUTIL package contains 2 methods for doing the global fringe fit:

  • VLBAFRNG does a fringe fit on every source in the observation
  • VLBAFRGP does a fringe fit on the phase-reference calibrator(s) and transfers those solutions to the science target(s)
VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBAFRNG
or VLBAFRGP 		FRING fringefit
CLCAL applycal


Bandpass Correction

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBABPSS BPASS bandpass


Final Amplitude Calibration

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBAAMP ACSCL accor
SNSMO smoothcal
CLCAL applycal
APCAL gencal
CLCAL applycal

Parallactic Angle Correction

VLBAUTIL Procedure AIPS Task(s) CASA Task(s)
VLBAPANG CLCOR
opcode 'pang'		 set parang=True in applycal, fringefit, and bandpass

Additional Tasks

AIPS Task CASA Task
SPLIT split
IMAGR tclean
CALIB gaincal
POSSM plotms
SNPLT plotms
UVPLT plotms
UVFLG flagadata
FITTP exportuvfits or exportfits
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