Radio Astronomy Interest Group

First Virtual Meeting 2020, July 2 via zoom

Telecon Agenda:

• Presentation of CASDA VO services (James Dempsey)
• Summary of radio-related IVOA meetings to date, including use cases for radio astronomy data in the VO (Mark Lacy)
• Needs of the community for implementing VO standards and protocols
  • what's needed from data providers to make data visible in the VO.
  • points of contact between Observatories and VO experts.
• Prototype of ObsTAP+DataLink services for visibility data discovery and access (F. Bonnarel)
• Metadata for radio data that are not currently part of the VO's core metadata set ("ObsCore", see the specification ), but might be needed to be added, or placed in a supplement.

Minutes

In both telecons, the discussions can be divided into more general remarks and discussions on VO implementation, and responses to Francois’ presentation on incorporating visibility data into the VO. As there was some overlap in the discussions, but also some different coverage I’ve merged the minutes from the two meetings below. The first meeting attracted 18 participants, the second 14. See the etherpad notes above for full details of attendence and the discussion.

Overview/intro to the VO in radio astronomy

How can data providers put their data into the VO? VO can provide software tools to help data centers with their archives. Would be good to have a tutorial/workshop aimed at telling the radio community what is available on terms of tools and how to use them, and for determining any special requirements for radio astronomy applications. Especially if it is aimed at the younger audience who will work on SKA and other large projects.

The NRAO summer school might be a good venue to give an introduction to radio data in the VO, along with similar schools in Europe. A list of upcoming events could be placed on the Radio Interest Group wiki.

Implementations:

CASDA/ASKAP (James) - TAP, cone search for catalogs, SIA-2 for cubes. Measurement set metadata is also kept, but not positions (for multi-object observations) or field of view information. The use of a single API for both the system and for astronomy users worked well, though it helped to start from scratch. Toolset available on github.

ALMA (Felix): TAP access with ObsCore and some extra column, implemented with help from CADC and CDS. Data hierarchy is complicated, and needs Datalink. Also making use of astroquery via TAP.

ASTRON (Yan): focus on surveys (e.g. LOFAR, APERTIF)

Nancy/NENUFAR(Baptiste): solar and solar system data with EpnCore, plus plans for an ObsCore table for NENUFAR

JIVE (Mark): ObsCore service for visibility data being set up.

INAF (Alessandra): working on data models for heterogenous datasets using CAOM, TAP and DataLink.

Several groups (Baptiste, Alessandra, James) working on pulsar data. James has a mapping of pulsar-FITS to ObsCore.

Baptiste suggested that an IVOA note could be written on these implementations.

Visibilities in the VO

More than one MS may be needed per observation (and vice-versa). Some MS are split by time, some by frequency. Radio astronomers tend to use frequencies rather than wavelengths, so Francois adds f_min and f_max to his ObsCore implementation. Field of view information may need improvement for low frequency telescopes with dipole antennas, where the field-of-view is often unrelated to the antenna size, and can be adjusted by beam-formers etc.

Radio astronomy has a variety of data formats, although the MS is the de-facto standard, it is not considered an archival format by its developers and is subject to change (though a more stable archival format is planned or the future). For now, ALMA and VLA use SDM, and VLBI FITSIDI. There is also a Pulsar-FITS standard too.

Would be good to have a tool that allowed you to visualize combinations of uv data (like a coverage map in the uv-plane).