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Knowledgebase: Archive & Data Retrieval
How can I get calibrated measurement sets to redo the imaging?
Posted by Felix Stoehr, Last modified by Sarah Wood on 15 March 2018 05:57 PM

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)imaging of the products will be required.

With the exception of Cycle 0, ALMA does not not store the calibrated visibilities (measurement sets) due to their size: they take up twice the amount of the raw data but contain very little additional information. Calibrated visibilities can be easily recreated by downloading the products and the raw data tar files and then running the scriptForPI.py using the correct CASA version. This procedure is also specified in the README file that is contained in each of the product tar files and in the ALMA QA2 Data Products document for each cycle, e.g. http://almascience.org/documents-and-tools/cycle3/ALMAQA2Products3.0.pdf .

Experience shows that downloading the raw data and recreating the visibilities is generally faster than it would be to download fully calibrated MeasurementSets.

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