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Overview of the virtual observatory course by Juan de Dios Santander Vela, and part of the MTAF (Métodos y Técnicas Avanzadas en Física, Advanced Methods and Techniques in Physics) Master at the University of Granada (UGR).
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Astronomy & StandardsInteroperability of astronomical dataJuan de Dios Santander Vela (IAA-CSIC)
Overview
Astrophysical records
Sharing astrophysical data
Interoperability standards
Astrophysical Records
Astrophysical records
Aurignacian Lunar Calendar / diagram, drawing after Marshack, A. 1970; Notation dans les Gravures du
Paléolithique Supérieur, Bordeaux, Delmas / Don’s Maps
Astrophysical records
In astrophysics, we record the EM radiation from distant objects, in order to:
understand the processes that generated the EM radiation
understand the processes that affect the received EM radiation
Many different records
Astrophysical records are different by means of their
EM/energy range (long vs. short-λ radio, IR, optical, UV, X-Ray, ɣ-Ray)
Product type (images, time series, spectra, spectral cube, image cube, combinations…)
Instrument setup
Many different records
Many, many things can change
Coordinate system, physical measurement, physical support…
And that’s just the observation generation!
Many different records
Most of those records can be represented as multi-dimensional arrays
Need to specify
Units
Sampling
Physical meaning
FITS: the Flexible Image Transport SystemHeader + Table data
Special case: Image data
Header: Keyword-value pairs
2-level hierarchies (Main HDU + Extensions)
NASA Standard + IAU Recommendation
FITS Keywords: BasicFITS
SIMPLEENDDATEBITPIXXTENSIONEXTNAMEEXTLEVELEXTVEREXTENDCOMMENTHISTORYBLOCKED
ProvenanceORIGINAUTHOROBSERVERDATE-OBSTELESCOPINSTRUMEOBJECTREFERENC
CoordinatesEPOCHEQUINOXNAXISNAXISnCTYPEnCRVALnCDELTnCRPIXnCROTAn
Tables & Images
BLANKDATAMINDATAMAXTFIELDS
BSCALEBUNITBZEROTFORMnTNULLnTBCOLnTHEAPTUNITnTDIMnTZEROnTDISPnTSCALnTTYPEnGROUPSGCOUNTPCOUNTPTYPEnPSCALnPZEROn
FITS Keywords: CommonFITS
TITLEFILENAMEFILETYPEROOTNAMEPROGRAMCREATORCONFIGURNEXTENDHDUNAMEHDUVERHDULEVELTLMINnTLMAXnTDMINnTDMAXnTDBINnTSORTKEYPROGRAMCREATORCONFIGURHDUCLASS
HDUDOCHDUVERSHDUCLASn
CHECKSUM DATASUMCHECKVER
GroupingsGRPNAMEGRPIDnGRPLCn
ProvenanceOBS_IDOBS_MODEDATAMODEAPERTUREDETNAMFILTERFILTERn
GRATINGGRATINGnSATURATE
TargetSUNANGLEMOONANGLRADECRA_NOMDEC_NOMRA_OBJDEC_OBJRA_PNTDEC_PNTPA_PNTRA_SCXDEC_SCXRA_SCYDEC_SXYRA_SCZDEC_SCZ
ORIENTATAIRMASSLATITUDEOBJNAME
Time & DateTIME-OBSTIME-ENDDATE-ENDEXPOSUREEXPTIMETELAPSEELAPTIMEONTIMELIVETIME
ConventionsHIERARCH INHERITCONTINUE
Curse of Flexibility
FITS can accommodate data from any instrument/telescope
but the price is semantics can be very different from instrument to instrument
initially solved through manuals for each instrument
this doesn’t scale for multi-λ astronomy
Astronomical Catalogues
Robert Grant: Catalogue of 6415 stars for the epoch 1870. Glasgow: James MacLehose & Sons, 1883. Pages 472-473,
beginning of the catalogue. Sp Coll MacLehose f8.
Astronomical CataloguesCollections of astronomical object properties
Typically, the result of many observations, or exhaustive treatment of all object in a observation
Main index types
Spatial
Temporal
Object template
Astronomical Catalogues
Explosion of catalogues since early ‘90s, thanks toDigitised astronomyInternet (FTP ➡ WWW)Journal tables
Astronomical CataloguesAstrometry
Photometry (no Radio)
Spectroscopy
Cross-Identifications
Combined Data
Miscellany
Non-stellar Objects
Radio Catalogues
High-Energy Catalogues
Journal Catalogues
Standardising Catalogues
Standardising
Naming
Column relationships (errors, bounds, notes…)
Dates & Units
SEMANT
ICS!
References & Links
FITS Standard Document
FITS World Coordinate System
FITS Dictionaries
Standard for Documentation of Astronomical Catalogues
UCD List