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Knowledgebase : Offline Data Reduction and/or CASA
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 [https://casa.nrao.edu/casadocs/casa-5.6.0/calibration-and-visibility-data/single-dish-calibra...
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 https://casa.nrao.edu [https://casa.nrao.edu] ) using task "impor...
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) & Total Power Data (TP) data and combining with 12-m data is described in the CASA Guide M100 Band3 [https://casaguides.nrao.edu/index.php/M100_Band3]. [https://casaguides.nrao.edu/index.php/...
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 the ...
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 use this file to edit variables and import modules you wan...
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...
Calibrated measurement sets are now directly provided by the ARCs. More information on the process is given below: The EU ARC: calibrated measurement sets can be requested through the Helpdesk [https://help.almascience.org/]. A detailed explanation is gi...
The ALMA TP data is generally reduced using the TP data reduction pipeline which performs calibration and imaging; only in exceptional cases are ALMA TP data manually reduced using standard scripts. Details regarding the calibration and imaging of TP data...
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 antenna ...
As described in Correlators chapter of the Technical Handbook [http://almascience.org/documents-and-tools/], 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 ...
A description for how visibility weights are defined and calibrated in CASA is available in this memo [http://casa.nrao.edu/Memos/CASA-data-weights.pdf] and as an appendix in the CASA cookbook [https://casa.nrao.edu/casadocs/casa-5.6.0/calibration-and-vis...
Beginning in CASA 5.6, tclean() has a new parameter _PERCHANWEIGHTDENSITY_ which has a default value of _TRUE_. Previous CASA versions did not offer per-channel UV-density weighting, and so in effect, _PERCHANWEIGHTDENSITY_ was _FALSE_. This Knowledgebase...
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. The link to the attachment is at the end of this article. If one takes independent channels, and ...
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...
Mosaic images of the 7-m array generated with CASA versions <5.1.1 (for the product images, these CASA versions were used in Cycles 1-4) and mosaic images of the both 12-m and 7-m array generated with CASA version 5.1.1 to 5.3 (for the product images, the...
Restoring the calibrated measurement set ------------------------------------------------- Calibration is the first step of processing interferometric data. Many users will want to recreate the calibrated measurement set and perform the second step (imag...
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 velocity ...
What you see in your data package when you download it from the archive will depend on whether the imaging and calibration have been performed by the pipeline, or one or both via a manual process. For Cycle 4 Imaging pipeline data and on, the products ar...
After downloading your data from the ALMA Archive you can check what version of CASA was used for the QA2 process in one of the following ways: * Check the qa2_report found in the qa directory * Check the README file at the MOUS level * Check the t...
A visibility amplitude calibration error originating in the combined effect of correlator spectral normalization and Tsys calibration has been discovered in ALMA interferometer observations (through cycle 7) of fields containing very strong astronomical e...
The global variables SPACESAVING, USEMS, and DOSPLIT 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 ASDM...
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 0.75...
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 [http://casaguides.nrao.edu/]. Of particular interest will be the ALMA CASAguides available here [http://casaguides.nrao.edu/index.php?title=ALMAguides]. You may find information ...
Representative array configuration files for Cycles 1 and after are linked to from the "CASA Simulator and Configuration Files [http://almascience.org/tools/casa-simulator]" section of the Tools page [http://almascience.org/tools] in the ALMA Science Port...
Since Cycle 5, the PI has had the ability to input a range of resolutions in the OT (a single value is considered a very tiny range). Based on this information, the OT writes a range of acceptable angular resolution into the Scheduling Block as follows: ...
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 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...