Radio Astronomy visibility data discovery and access using IVOA standards

Radio astronomical archives for large facilities (VLA, ASKAP, LOFAR, JIVE, MeerKAT) used to mostly store raw or calibrated visibility data . However, the situation is changing and some facilities (e.g. ALMA), store and distribute science ready data. This will also be the case for future radio telescopes, like SKA, where calibrated and imaged data products will be provided. Naturally, the major goal of these archives is to make their data discoverable and accessible to the astronomy community. Today, many archives give access to visibility data with project-specific web interfaces in order to allow users to reprocess the data with fine tuned reduction parameters.
Science platforms such as ESAP developed within the ESCAPE (\footnote{ }) project will allow this.
IVOA decided to make integration of radio astronomy data in the Virtual Observatory (VO) a science priority. Various radio astronomers and projects (NRAO, ASKAP, LOFAR, JIVE, ALMA, SKA, INAF, NenuFAR \footnote{ }, etc.) joined the Radio Astronomy Interest Group of the IVOA, which was recently founded. Together they are paving the way to a better integration of their services in the VO infrastructure and are proposing evolution of IVOA standards to help achieving this goal.

In this context CDS created a prototype for exposing visibility data observations, split in a consistent list of datasets in an ObsTAP service, for coarse grain discovery. Additional metadata such as number of antennae, frequency ranges, uv_density plots, frequency-phase and frequency-amplitude plots, primary and synthesized beams are also provided either by adding column metadata or by using the DataLink technique (\footnote{ }).

This presentation describes the process of metadata integration in the system, explores how to extend the ObsCore data model specification for radio visibility data and details the choices which have been made. We furthermore show results of data selections through various VO applications. We conclude with the possible evolutions of the prototype and lessons learnt from this exercise.
authors :
Mireille Louys, Katarina Lutz, Yelena Stein, Anaïs Egner and François Bonnarel

Theme – Data Interoperability