Simple Spectral Access Protocol

Simple Spectral Access Protocol
Name	Simple Spectral Access Protocol
Acronym	SSA
Developer	International Virtual Observatory Alliance
Introduced	2002
Latest release	IVOA Recommendation
Genre	Astronomical data access protocol

Contents

Simple Spectral Access Protocol

Simple Spectral Access Protocol provides a standardized web-service interface for discovery and retrieval of one-dimensional astronomical spectra and spectral energy distributions across distributed archives. Its design enables interoperability among archives operated by institutions such as European Southern Observatory, Space Telescope Science Institute, National Aeronautics and Space Administration, European Space Agency and data centers like Centre de Données astronomiques de Strasbourg, while aligning with standards from bodies including International Virtual Observatory Alliance, International Astronomical Union, and Committee on Data for Science and Technology.

Overview

SSA defines a RESTful query model and response metadata to allow clients to search for spectral datasets from archives such as Sloan Digital Sky Survey, Gaia, Hubble Space Telescope, Chandra X-ray Observatory, and James Webb Space Telescope. The protocol specifies query parameters for spatial, temporal, spectral, and observational constraints used by services hosted at centers like Infrared Processing and Analysis Center, NASA/IPAC, Max Planck Institute for Astronomy, Harvard-Smithsonian Center for Astrophysics, and National Radio Astronomy Observatory. SSA responses reference data objects archived by projects including 2MASS, WISE, ALMA, LOFAR, and Keck Observatory.

The protocol evolved within the International Virtual Observatory Alliance working groups influenced by earlier initiatives at European Southern Observatory, Space Telescope Science Institute, Centre de Données astronomiques de Strasbourg, and national agencies such as NASA and ESA. Early requirements drew on use cases from surveys like Sloan Digital Sky Survey and missions including Hubble Space Telescope and Chandra X-ray Observatory, with formal recommendations published following community review periods that included contributors from Harvard-Smithsonian Center for Astrophysics, Heidelberg Institute for Theoretical Studies, and Max Planck Society. Subsequent revisions addressed interoperability with standards from World Wide Web Consortium and metadata practices advocated by Committee on Data for Science and Technology.

SSA specifies query operations such as "queryData" and "getData" implemented over HTTP endpoints hosted by archives like European Space Agency, NASA/IPAC, National Radio Astronomy Observatory, and Space Telescope Science Institute. The specification prescribes parameter names for coordinates referencing catalogs like Gaia and Hipparcos, spectral ranges aligned with instrument archives at Hubble Space Telescope and James Webb Space Telescope, and output formats compatible with tools used at institutions such as Centre de Données astronomiques de Strasbourg and Harvard-Smithsonian Center for Astrophysics. Error handling and service capabilities are defined to interoperate with registry systems maintained by International Virtual Observatory Alliance and discovery services used by projects like Sloan Digital Sky Survey.

SSA leverages data models and serializations common in the virtual observatory ecosystem, mapping spectrum metadata to standards interoperable with Flexible Image Transport System, VOTable, and formats supported by archives such as European Southern Observatory and NASA. The model encodes provenance and observational metadata compatible with archives like ALMA, Keck Observatory, and Chandra X-ray Observatory, and aligns with semantic constructs used by International Virtual Observatory Alliance data models and registry records curated at Centre de Données astronomiques de Strasbourg. Output formats enable ingestion by analysis tools developed at institutions including Harvard-Smithsonian Center for Astrophysics, Max Planck Institute for Astronomy, and software projects originating at Space Telescope Science Institute.

Public SSA services are implemented by major archives and projects such as Sloan Digital Sky Survey, Hubble Space Telescope archive at Space Telescope Science Institute, Gaia (spacecraft) archive at European Space Agency, Chandra X-ray Observatory archive at Harvard-Smithsonian Center for Astrophysics, and radio facilities like ALMA and LOFAR. Software libraries and toolkits that support SSA clients have been developed within communities at Centre de Données astronomiques de Strasbourg, European Southern Observatory, Max Planck Institute for Astronomy, and independent projects associated with NASA. Registries that list SSA endpoints are maintained by working groups of the International Virtual Observatory Alliance and referenced by portals run by NASA/IPAC and ESA Science.

SSA enables cross-archive spectral discovery and multi-mission science such as time-domain spectroscopy comparisons between Hubble Space Telescope, James Webb Space Telescope, and ground-based facilities like Keck Observatory and Very Large Telescope. Surveys like Sloan Digital Sky Survey and missions such as Gaia (spacecraft) and WISE rely on SSA-compatible services to support spectral energy distribution assembly and archival research at centers including Harvard-Smithsonian Center for Astrophysics, European Southern Observatory, and Centre de Données astronomiques de Strasbourg. Scientific applications span stellar population studies using data from Hipparcos and Gaia (spacecraft), extragalactic spectroscopy leveraging Sloan Digital Sky Survey and James Webb Space Telescope, and multi-wavelength analysis combining Chandra X-ray Observatory and ALMA datasets.

SSA implementations hosted by organizations such as Space Telescope Science Institute, European Space Agency, NASA, and National Radio Astronomy Observatory must address authentication and authorization integration with identity providers used across research infrastructures at European Southern Observatory and national data centers. Interoperability relies on conformance to metadata registries curated by International Virtual Observatory Alliance and compliance testing frameworks adopted by archives like Centre de Données astronomiques de Strasbourg and NASA/IPAC. Handling of proprietary periods and access control intersects with policies set by projects including Hubble Space Telescope and ALMA and legal frameworks overseen by agencies such as European Space Agency and national research councils.

Category:Astronomical protocols