Since 2020, the EU ARC offers a service which permits ALMA users to request the calibrated data for a given dataset (Member Obs Unit Set, MOUS) to be made available for download.

The service is open both for ALMA PIs or Delegees with proprietary ALMA data and for archival users wanting to use datasets for which the proprietary time has expired. Calibrator data can also be requested before the end of proprietary time (see below).

If you have identified a particular MOUS that you want to investigate, please file a normal Helpdesk ticket in the department "Archive and Data Retrieval (EU)" and select the "Data request" sub-category.

In the body of the text always specify the project code (e.g. 2015.1.09999.S, one per ticket) and  MOUS UID(s) (e.g. uid___A001_X340_X6 or uid://A001/X340/X6). You can enumerate up to 10 MOUSs in your request.

The creation and staging will be done one MOUS at a time and you will be notified by separate email for each MOUS as to where you can download the tarred MS(s).
Depending on the workload on the EU ARC systems, it may take days before your dataset is ready for you. However, the typical time is ca. 24 h.
 
Your download link will remain valid for 21 days, which means that you have 21 days from the time of the notification email to download the data.

The service features are extended regularly. Consult the README file included in the staged set of files to learn more about the dataset.

Special pipeline visibility products

For all Pipeline-imaged MOUSs , all pipeline-generated calibrated data will be generated and provided. Please refer to the ALMA pipeline documentation for details on products beyond the standard calibrated data. They may include (depending on the Cycle) continuum-subtracted and/or self-calibrated visibilities. Using these additional MSs, users can immediately profit from an advanced continuum subtraction for line observations, and from reduced noise levels obtained by self-calibration.

Calibrator data from MOUSs in proprietary time

General archive researchers can request the calibrated data for particular calibrator targets even if the MOUS is still in proprietary time: If a user is interested in the data of a certain calibrator target (typically a Quasar) which is contained in an MOUS which is still in proprietary time, but the user is not part of the PI team and thus not entitled to access the science target data of the MOUS, then he/she can still request the calibrated data for the calibrator only. Just add the text "requesting only the data for calibrator <name>" to your helpdesk request where <name> is the exact name of the calibrator, e.g. "J0217-0820", as it can be determined from the Archive.

Identifying Group OUS members

You can identify MOUSs which belong to the same Group OUS from tags which the CalMS service writes into the MS's HISTORY table.

Calibrated data for MOUSs from Cycles 1 - 4

The calibrated data for the MOUSs from Cycles 3 and 4 as well as ca. 70% of the MOUSs from Cycle 2 were stored by the Ari-L project in a tape library at INAF, Bologna. This system has a rapid response time at least as fast as restoring the data from the raw data.

The ESO CalMS system was used over the course of 2023 to also create a complete set of calibrated data for Cycle 1, and in 2024 to generate the calibrated Cycle 2 data missing at INAF. This calibrated Cycle 1 and 2 data is being added to the INAF holdings.

The CalMS service will forward your requests for MOUSs from Cycle 1 - 4 to INAF if they are part of their holdings.

You will then receive an email from domain "inaf.it" that contains the download link. The staged calibrated data will remain available for download from INAF for 7 days.

The way how you request MOUSs from CalMS remains unchanged. Should an MOUS not be available from INAF, it will be restored for you by the CalMS system at ESO as usual.

Caveat on MOUSs from Cycles 1 and 2

If the data you are interested in was calibrated with a CASA version < 4.3 (Cycle 1 and 2) and you are planning to combine it with other interferometric data from a different MOUS, please be aware of the issues described in
https://casaguides.nrao.edu/index.php/DataWeightsAndCombination and consult an expert (e.g., your local ARC node or the ALMA helpdesk).