VO Course 02: Astronomy & Standards

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