International Virtual Observatory Alliance
The Simple Spectral Access (SSA) Protocol (SSAP) defines a uniform interface to
remotely discover and access one dimensional spectra. SSA is a member of an
integrated family of data access interfaces altogether comprising the Data
Access Layer (DAL) of the IVOA. SSA is based on a more general data model
capable of describing most tabular spectrophotometric data, including time
series and spectral energy distributions (SEDs) as well as 1-D spectra; however
the scope of the SSA interface as specified in this document is limited to
simple 1-D spectra, including simple aggregations of 1-D spectra.
The form of the SSA interface is simple: clients first query the global
resource registry to find services of interest and then issue a data
discovery query to selected services to determine what relevant data is
available from each service; the candidate datasets available are described
uniformly in a VOTable format document which is returned in response to the
query. Finally, the client may retrieve selected datasets for analysis.
Spectrum datasets returned by an SSA spectrum service may be either precomputed,
archival datasets, or they may be virtual data which is computed on the fly to
respond to a client request. Spectrum datasets may conform to a standard data
model defined by SSA, or may be native spectra with custom project-defined
content. Spectra may be returned in any of a number of standard data formats.
Spectral data is generally stored externally to the VO in a format specific to
each spectral data collection; currently there is no standard way to represent
astronomical spectra, and virtually every project does it differently. Hence
spectra may be actively mediated to the standard SSA-defined data model at
access time by the service, so that client analysis programs do not have to be
familiar with the idiosyncratic details of each data collection to be accessed.
Simple Spectral Access
IVOA Proposed Recommendation 17 April 2011
- Interest/Working Group:
- Doug Tody, Markus Dolensky, Jonathan McDowell, Tamas Budavari, Ivan Busko, Alberto Micol, Pedro Osuna, Jesus Salgado, Petr Skoda, Randy Thompson, Frank Valdes, and the Data Access Layer Working Group.
- Doug Tody
This is an IVOA Proposed Recommendation made available for public review.
It is appropriate to reference this document only as a recommended standard that is under review and which may be changed before it is accepted as a full recommendation.