We have developed a sophisticated system that automatically generates calibrated ALMA observation data called “calibrated MeasurementSet” (MS) by simply inputting the unique identifier of the dataset.
The ALMA Science Archive ( almascience.org ) serves users with raw observation data, pipeline or manually reduced products including FITS images of science targets, and scripts to restore calibrated MS which is required to create FITS images. Users should execute the script by themselves on their own computers to obtain calibrated MS, since they are not served by the Science Archive. With our new system, users only have to specify the data set and run a command on the provided platform, and the data is ready to go. There is no need to download the data to restore calibrated MS, nor to prepare their own environment for it.
The script requires the same data reduction software (CASA: Common Astronomy Software Applications) including its version with which the product was created. Since there is a strong dependency between the versions of CASA and the operating system (OS), the end of life (EoL) of a certain OS could prevent the users from restoring the MS for ALMA. RedHat Enterprise Linux 6 and equivalents are planned to end their lives in November 2020, which may risk the users who need to restore the data processed with a certain version of CASA with this OS. To overcome this problem, series of CASA distributions tied to shortly obsolete OS are containerized using Docker technology to make them work on more recent versions of OS. As long as the Linux kernel remains backward compatible in the future, the container can be made to work. Keeping the software in a condition to work in the future, it is important to ensure the reproducibility of archived products in the future.
Since April 2020, for the dataset being reduced with previous versions of CASA, East-Asian ALMA Regional Center (EA-ARC) is starting a service to generate and provide the calibrated MS files upon the request from users of ALMA. The system has recently been deployed in EA-ARC to facilitate their operation. Users of ALMA have the benefit of this system through the service provided by EA-ARC.