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Knowledgebase : Offline Data Reduction and/or CASA
Data observed from 03 January, 2017 (with DA42) and from 25 December, 2016 (with DA50) until the February 2017 shutdown (31 January 2017), and that was run through either manual or pipeline calibration and imaging prior to 21 February, 2017, will have ...
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 for Cycle 0 data: * 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 C...
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 t...
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...
The FITS products delivered to the PIs are not complete. They mostly serve the purpose to show that the requested parameters are reached and do not always cover the full bandwidth, all spectral windows, or all fields. For many scientific use-cases, (re...
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. ...
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 ...
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...
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...
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 Correlators chapter of the 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, Bl...
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. More information can be found in the Data Weights And Combination CASA ...
Below is a short explanation for how noise is correlated in CASA with mstransform and tclean, and attached is a PDF file with more detailed information. If one takes independent channels, and interpolates between them, one obtains correlated channe...
You can create your own copy of the Observatories table by taking it from the "/data/geodetic" directory in your CASA installation and then editing your copy with the browsetable task in CASA. Once you have your own copy, e.g. in the directory "/home/m...
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 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 -12dB taper and 0...
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...
For projects that were imaged using the pipeline after April 2017, scriptForPI.py may produce an error when trying to restore data. --------------------------------------------------------------------------- RuntimeError Traceback (most recent call last...
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 for Cycles 1 and after are linked to from the "CASA Simulator and Configuration Files [1]" section of the Tools page [2] in the ALMA Science Portal. Configuration files for Cycle 0 are available from the Cycle 0...
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 ...
The behavior of hifa_restoredata (formerly hif_restoredata) has been changed such that starting with CASA 5.1.1, it now requires the pipeline manifest in order for it to work. The old hif_restoredata has been removed from 5.1.1, which means the ability to...
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 scriptForP...
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...