VizieR asteroid spectra

The VizieR asteroid spectra collection is a compilation of spectra associated to publications, and distributed by the VizieR catalogue service at CDS, Strasbourg. The current data service provides simple and easy access to this data and powerful search functions from the VESPA portal, including cross-matches with other services of similar content.

Virtual Observatory service

VizieR stores catalogues of data published in astronomy science papers and make them available in the Virtual Observatory (VO). Although VizieR has handy search and display functions, accessibility heavily depends on the way the data have been prepared; in particular spectra nested in catalogues are difficult to access uniformly. This Virtual Observatory service has been set up to provide easier access to these spectra and to allow cross-matching with similar services of different origin.

The collection is presented in a table with descriptive parameters for each spectrum:
– Each line links to a single spectrum
– Observing conditions have been retrieved from the original papers whenever possible
– Bibliographic references are included as bibcode (used by ADS)
– Thumbnails have been produced to provide a quick visual diagnostic in the search interface

Spectra can be provided in two formats:
– either as fits files produced by VizieR when available;
– or as VOtable when VizieR only provides an ascii version.
Both formats are self-described and can be handled by VO tools.
A link to the original repository is provided under external_link (VizieR in general, JAXA in one case). This provides access to the native ascii format which may include additional information, such as calibration flags.

– The data are not recalibrated, in particular the original “flux” axis is preserved. This is not homogeneous in the library (i.e., some spectra are in flux or radiance, some are in reflectance or emissivity, some are normalized, etc).

The service table is formatted according to the EPN-TAP standard, which implies that column names and units are standardized. The data service can be queried using the TAP protocol, in particular from the VESPA portal of Solar System data: http://vespa.obspm.fr/
See the complete data service in the VESPA portal (the schema name is spectro_asteroids).

A tutorial for spectral studies in the Planetary Science VO context is available here:
http://voparis-europlanet.obspm.fr/utilities/Tuto_Spectro_VESPA.pdf
In particular with the CASSIS tool:
http://voparis-europlanet.obspm.fr/utilities/Tuto_CASSIS_VESPA.pdf

In short: you first identify data of interest from a search interface, then send selected results in a visualization and analysis tool. The plotting tools of choice for spectra are CASSIS and SPLAT-VO, which can handle conversions of the spectral axis (TOPCAT may also be convenient).

Looking for spectra

Searches based on decriptive parameters can be performed from the VESPA portal or any TAP interface (TAPhandle, TOPCAT, etc). A specific EPN-TAP client is also installed in the CASSIS spectral tool.
Query results are tables, with a line describing each match. The column access_url provides a link to the spectrum.

Important search parameters include:
target_name – name provided in the paper, usually the standard IAU name of the objet or its principal designation
alt_target_name – other designations – the SSODnet name resolver (available from the VESPA portal) can disentangle various designations
spectral_range_min / spectral_range_max – limits of the spectral range (given in Hz in the table, convertible to µm in the portal)
spectral_resolution_min / spectral_resolution_max – estimate of (delta lambda) / lambda.
measurement_type – measured quantity provided as a UCD
data_calibration_desc – contains short information as a free format comment
access_format – indicates VOtable or fits format (Mime type)
granule_gid – reference of the VizieR catalogue, indicating the origin of the data
granule_uid – a unique identifier derived from the original paper

Data included

Modern collections of asteroid spectra distributed by VizieR were extracted and gathered in the table. There are currently 8 such data collections corresponding to different articles.

The original data calibration is preserved, and data are provided either as flux, radiance, reflectance or emissivity, and are sometimes normalized. Scaling is indicated in the parameter data_calibration_desc.
The spectral axis in the files is always wavelength in µm.

Additional spectra of asteroids and dwarf planets are available in other EPN_TAP data services, e. g., M4ast or HST_planeto. They can be queried simultaneously from the VESPA portal.

Possible extensions

The current data service will be improved by adding more catalogues from VizieR – contact the helpdesk for comments: support.vespa@obspm.fr

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This data service is provided in the framework of the VESPA activity in Europlanet-2024 by Paris Astronomical Data Centre (PADC)

The Europlanet-2024 Research Infrastructure project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 871149. Additional funding was provided in France by the Action Spécifique Observatoire Virtuel and Programme National de Planétologie / INSU.    


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