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Knowledgebase : Offline Data Reduction and/or CASA
     
There are three main advantages to using CASA 3.4 or later when reducing ALMA Cycle 0 data that may have originally been reduced in earlier versions of CASA: * In CASA 3.4 the primary beam models used in CASA were improved to better account for the...
Yes there are three main issues to be aware of: * A major refactor of the calibration table format and functionality took place between CASA 3.3 and CASA 3.4. Calibration tables created in CASA 3.3 (and earlier) cannot be used in CASA 3.4 and later...
It is possible to reduce single dish ALMA data using tasks within CASA. Information on these tasks and tools can be found in the CASA User Reference & Cookbook [1]. Links: ------ [1] http://casa.nrao.edu/ref_cookbook.shtml
You can reduce data in packages other than CASA, such as AIPS, Gipsy, or Miriad. First, get the data from the ALMA archive. It will be in the "ASDM" format. Read it into CASA (obtained from http://casa.nrao.edu/current_casa.shtml) using task "importasdm"...
If you are in "optical" mode in the CASA viewer spectral profiler, only the moments sum, mean, and median are offered. If you want others, you need to switch to "non-optical" mode: Click on the "toothed wheel" icon at the top of the window (4th from the...
There is no difference in the feathering process between the Solar and other observations, except for the case that the field of view is very near the solar limb (< the diameter of the primary beam). For the limb observations, you might need to apply the ...
The process of calibrating and imaging ALMA Compact Array (ACA) data and combining with 12-m data is described in the CASA Guide M100 Band3 Combine 4.3 [1]. [2] Links: ------ [1] https://casaguides.nrao.edu/index.php/M100_Band3_Combine_4.3 [2] https:/...
The easiest way to calculate the spectral coverage of one or more SPWs in different frequency reference frames is by using plotms or viewer. For a measurement set, plotms will plot data as a function of frequency using the reference frame selected in t...
A small fraction of Cycle 0 data sets have been found to be impacted by a bug in the CASA 3.4 task 'tflagdata'. When 'tflagdata' in CASA 3.4 was used to flag SHADOWED antennas, instead the SHADOWING antennas were flagged. The impact of this bug on deli...
In your home directory you have a directory called ~/.casa/ This directory contains a file called "init.py" that executes each time you start CASA, just before the prompt is displayed. You should used this file to edit variables and import modules y...
In order to tell for sure which version of CASA was used for calibration and imaging, check the data reduction script. The data were calibrated and imaged in, for example, CASA 3.4 if the script contains the line: if re.search('^3.4', casadef.casa_ver...
How can I update Cycle 0 absolute fluxes to the Butler-JPL-Horizons 2012 model standards? Cycle 0 data reduction was done using CASA versions 3.3 and 3.4, which use the Butler-JPL-Horizons 2010 models to set the flux model for solar system objects. ...
Up to and including CASA 4.3 on Linux it has been possible to update the data repository of a CASA installation (including for example the leap seconds table) by typing at the shell prompt svn update in the "data" directory. This scheme will be...
If you reported a CASA bug or requested a new feature through the helpdesk and were told the developers have been notified, you can check development team progress here [1]. Search for your helpdesk ticket number in the top right of this webpage and...
To accurately combine ALMA data requires that the visibility weights for each set of data be calculated in the same manner. Unfortunately, the method used by CASA to calculate weights has evolved with time. Depending on the circumstances, combination o...
If your observations consist of multiple execution blocks (EBs) for the same target source with the same antenna configuration and spectral setup, combining those executions can help reach your proposed sensitivity. There are two primary methods of ima...
The following two visibility flagging issues were found in the ALMA data analysis done with the CASA package. The issues do not invalidate science results but they may have reduced the sensitivity of your observation. Since delivered datasets did pass ...
The simobserve task reads the antenna locations from a configuration file specified by the parameter "antennalist." This is a plain text file which lists x, y, and z coordinates for each antenna as well as antenna diameter and pad name. A list of anten...
As described in Section 5.5.2 of the Cycle 3 Technical Handbook [1], the window function in the ALMA correlator is applied to the time domain (lag domain) data. The Hann window is the default window, but others are available : Uniform, Hamming, Welch, ...
A description for how visibility weights are defined and calibrated in CASA is available in this memo [1] and as an appendix in the CASA cookbook [2] from version 4.2.2 onwards. NOTE: The treatment of weights depends on which version of CASA is used...
You can create your own copy of the Observatories table by taking it from the "
Due to a very subtle bug in CASA 4.7.0 which was introduced in the packaging of the release tarball after all tests had passed, exportfits writes FITS files which contain a carriage return (CR) character. This is illegal according to the FITS standard ...
Before ALMA Cycle 3, the position reference frame in MeasurementSets and Images was given as J2000. However, since the actual position reference frame of the phase calibrators used in the observations was ICRS, it was found that this label was misleadi...
Here is a little script "demo_imageregrid.py" to demonstrate how to make the grids of two images agree. The script first creates its own test data by generating two images with different coordinate systems and angular grids but with a pattern of the sam...
ALMA Cycle 0 PI or Science Verification data may have been reduced in an earlier version of CASA. In this case, the scripts that were provided in the original data delivery will most likely not work with later versions of CASA (see the Knowledgebase ar...
Sometimes packages that are distributed within the CASA installation (such as IPython, numpy etc.) become confused with non-CASA installations upon starting or working in CASA. Error messages like CASA Version 4.2.2 (r30986) Compiled on: Thu 2014/0...
CASA offers the following frames: * BARY - Solar System Barycenter, referenced to JPL ephemeris DE403. Only slightly different and more accurate than heliocentric. * LSRK - Kinematic LSR, conventional local standard of rest based on average veloc...
The global variables SPACESAVING and USEMS can be set prior to executing scriptForPI.py. The variables can be used independently or in conjunction. USEMS can be set to use pre-imported measurements sets(MS) rather than import them from the ASDMs in ...
The voltage pattern assumed by CASA (≤ version 4.3.1) for the ALMA 12-m primary beam is currently hard coded to a uniformly illuminated 10.7-m dish with 0.75m blockage, resulting in an Airy disk whose FWHM is SIMILAR to a 12m Gaussian illumination with...
Messages like SEVERE setjy Leap second table TAI_UTC seems out-of-date. SEVERE setjy Until table is updated (see aips++ manager) times and coordinates SEVERE setjy derived from UTC could be wrong by 1s or more. on Linux installations of CASA i...
In CASA versions BEFORE 4.3 there is a problem with libxml on some Linux distributions other than RHEL 5 and 6, e.g. Ubuntu 13 and Fedora 20. The libxml version shipped with CASA does not work with other system libraries. You will need to do the follow...
Data reduction manuals and recipes can be found at the CASAguides website [1]. Of particular interest will be the ALMA CASAguides available here [2]. You may find information on tutorials/workshops at * North America: NRAO Community Outreach Events...
Representative array configuration files are linked to from the "Array Configuration Files" section of the Documents and Tools page [1] in the ALMA Science Portal. Configuration files for Cycle 0 are available from the Cycle 0 Documentation page [2]. W...
It was recently discovered that the ACA 7m configuration files for Cycle 4 in the casa simulator use an incorrect primary beam, so 7m simulations may have incorrect fluxes. Simulations of the 12m array are fine. In order to fix the problem, the first l...
In CASA 4.1 channel (spectral or velocity) averaging is done by the task split, while the cvel task only interpolates the data onto a new frequency grid. To achieve both channel averaging and to move the data to a new frequency grid, one must combine s...
This is to notify all CASA users that a bug was dicovered in the code underlying the field selection mechanism in the clean task. The bug is present in CASA 3.4, 4.0, and 4.1 and affects the flux scaling and restoring beam calculations in clean. Thi...
The error message NameError: name 'h_init' is not defined indicates you are trying to execute pipeline tasks that CASA does not recognize. To verify that your active CASA session includes pipeline tasks please type tasklist at the CASA prompt. I...
The CASA task _exportfits _sets the header keyword BUNIT as 'JY/BEAM' in CASA 4.2 and earlier, whereas it is 'Jy/beam' in CASA >=4.3. The BUNIT keyword is case-sensitive and 'Jy/beam' is adopted as FITS standard. This change of the units can cause ...
Due to a change in CASA, the task hif_restoredata now searches for calibration files with the extension *.tgz. Data products that were produced using CASA versions prior to 4.7.0 contain calibration files with the extension *.tar.gz. This leads scriptF...
Cycle 0 data was processed by ALMA science staff using CASA, with scripts that reflect the best practices in ALMA data reduction. However, improvements and bug fixes to CASA are made over time, and users may wish to reprocess their data with a more rec...
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