VOTable

VOTable
Name	VOTable
Developer	International Virtual Observatory Alliance
Released	2002
Latest release	IVOA VOTable 1.4 (2013)
Operating system	Cross-platform
Genre	Data interchange format
License	IVOA recommendations

VOTable

VOTable is an XML-based data format designed for the interchange of tabular data in astronomy. It facilitates interoperability among observatories, archives, catalogues, and analysis tools by encoding astronomical tables, metadata, and provenance in a machine-readable form. The format is widely used by organisations, missions, and projects that require standardized exchange of catalogue entries, spectra, and time series.

Overview

VOTable was created to serve the needs of the Space Telescope Science Institute, European Southern Observatory, National Aeronautics and Space Administration, European Space Agency, and other institutions for interoperable data sharing. It integrates with initiatives such as the International Virtual Observatory Alliance and complements protocols like the Simple Image Access Protocol, Table Access Protocol, and Simple Spectral Access Protocol. VOTable documents describe table schemas, column metadata, units, UCDs, and coordinate systems, enabling use by software from projects at the Harvard–Smithsonian Center for Astrophysics, Max Planck Institute for Astronomy, Centre de Données astronomiques de Strasbourg, and national data centres.

History and Development

Development of VOTable began in the early 2000s within the International Virtual Observatory Alliance working groups, drawing on prior formats used by the European Southern Observatory and archives such as the Mikulski Archive for Space Telescopes and the SIMBAD database. Key contributors included teams from the Centre de Données astronomiques de Strasbourg, Space Telescope Science Institute, and members from the National Radio Astronomy Observatory. Major milestones include the original recommendation in 2002, revisions to support binary serialisation influenced by implementations at the European Space Agency and CERN, and the VOTable 1.3/1.4 refinements that aligned with practices at the Sloan Digital Sky Survey and the Gaia mission archives.

Format and Structure

A VOTable document is an XML container that organises one or more RESOURCE elements, each containing TABLE elements that in turn hold FIELD and DATA components. FIELD metadata employ UCDs developed by standards bodies associated with the International Astronomical Union and units consistent with conventions used by the NASA/IPAC Extragalactic Database, Two Micron All-Sky Survey, and major survey projects. DATA can appear as TABLEDATA (element-wise XML), BINARY, or BINARY2 serialisations that provide compact representations used by high-throughput services at the European Space Agency and the National Radio Astronomy Observatory. VOTable supports LINK elements for external references to services like the Virtual Observatory Registry entries maintained by the AstroGrid and the Observatoire de Paris.

Usage and Applications

VOTable is used extensively in catalogue dissemination by projects such as the Sloan Digital Sky Survey, Gaia, Pan-STARRS, Two Micron All-Sky Survey, and archives like the Mikulski Archive for Space Telescopes and European Southern Observatory Science Archive Facility. It is embedded within workflows for spectroscopic pipelines at the Keck Observatory and time-domain services associated with the Zwicky Transient Facility and Large Synoptic Survey Telescope collaborations. VOTable underpins cross-matching tasks performed by tools from the Centre de Données astronomiques de Strasbourg and the National Optical Astronomy Observatory, and it is used to exchange calibrated light curves, spectral line lists, and simulation catalogues produced by centres such as the Max Planck Institute for Astrophysics and Lawrence Berkeley National Laboratory.

Software and Tools

A broad ecosystem supports VOTable, including libraries and applications from the Astropy project, the TOPCAT and STILTS packages developed by the University of Bristol and the Centre de Données astronomiques de Strasbourg, and VO-enabled services in the IRAF and CASA environments. Client libraries exist in languages maintained at institutions like Google, Microsoft Research, and academic groups at Princeton University and Cambridge University. Server-side implementations are integrated into Apache-based archives hosted by the European Space Agency and repositories at the Space Telescope Science Institute. Visualization and analysis tools such as Aladin and the WorldWide Telescope support VOTable ingestion for interactive exploration.

Governance and Standards

VOTable is specified and maintained under the auspices of the International Virtual Observatory Alliance, with guidelines shaped by working groups including representatives from the European Space Agency, National Aeronautics and Space Administration, Centre de Données astronomiques de Strasbourg, and national observatories like the National Radio Astronomy Observatory and Australian Astronomical Observatory. The specification aligns with XML recommendations endorsed by the World Wide Web Consortium and interoperates with registry standards maintained by the International Virtual Observatory Alliance and metadata vocabularies influenced by the International Astronomical Union commissions.

Examples and Sample Files

Typical VOTable examples are distributed by the Centre de Données astronomiques de Strasbourg and appear in tutorials from the International Virtual Observatory Alliance, Astropy documentation, and workshops held at institutions such as the Space Telescope Science Institute and European Southern Observatory. Sample files illustrate TABLEDATA for small catalogues, BINARY serialisations used by large surveys like Gaia and Sloan Digital Sky Survey, and BINARY2 examples for mixed null-value handling used by the Pan-STARRS and Zwicky Transient Facility teams. Many archive services provide downloadable VOTable endpoints via the Table Access Protocol and examples in the Virtual Observatory Registry.

Category:Astronomical catalogues