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What does LOFAR have to do with the Virtual Observatory (VO)?

Learn how LOFAR, a radio telescope, is integrated with the Virtual Observatory (VO) standards, enabling data retrieval, data models, registries, and grid computing. Explore the vision of a VO utopia with diverse data and tools that are interoperable and accessible through standard mechanisms.

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What does LOFAR have to do with the Virtual Observatory (VO)?

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  1. What does LOFAR have to do with the Virtual Observatory (VO)? LOFAR Science Day 16 December 2003 Melbourne David Barnes The University of Melbourne

  2. VO is Standards (1) • data description • metadata, content tags, context tags • IVOA: VOTable, UCD WGs • data retrieval • http, ftp, web services, replica catalogs • IVOA: Data Access Layer, Grid & WS WGs • data models • structure and relationships in data • IVOA: Data Modelling WG

  3. VO is Standards (2) • data and service compilation and indexing • registries, resource description • IVOA: Registry WG • finding data and services • VO Query Language, SQL, brokers, agents • IVOA: VO Query Language WG • workflow and interface • portals, portlets, authentication, authorisation • IVOA: no WG yet

  4. VO is Grid Computing • local, national, global compute grids • transparent, secure access to processors • job submission & monitoring, workflows • local, national, global data grids • replica catalogues (caching) • global filesystems • local, national, global networks • move code to data or data to code • realtime client-server processing, analysis and visualisation

  5. VO Utopia (1) • diverse data (eg. X-ray photon event lists and SPH cosmo simulation) • found in standard VO registries • described using standard vocabulary • tagged with pointers into a standard astronomy data model • accessed via standard mechanism eg. SOAP query to Web Service • provided in standard storage format, eg. VOTable, HDF, FITS, … • data sets are interoperable

  6. VO Utopia (2) • diverse tools (eg. source extractor, volume visualiser, PCA algorithm) • found in standard VO registries • described using standard vocabulary • tagged with pointers into a standard astronomy data model • accessed via standard mechanism eg. SOAP query to Web Service • read and writestandard storage format, eg. VOTable, HDF, FITS, … • tools are interoperable • tools AND data are interoperable

  7. VO Utopia (3): LOFAR • naif: registry search : LOFAR exists! : free data is available! • traditionalist: query LOFAR archive via VO, download images and analyse at home • aspirant: use on-line VO LOFAR pipeline to recalibrate intermediate data product/s and re-image with modified visibility weights • braveheart: incorporate any or all LOFAR data products in VO workflows exploiting several other data sets at once

  8. VO Utopia (4): LOFAR • Grid: this data is popular in France : replicate data product @ CDS : provide transparently to UK users • Grid: this data is owned by David and in propietary period : you can’t have it yet • Grid: you have requested 4 TB of data : click here to upload and run your code at the data centre rather than fetching for days. • Telescope: “I am just a long-queue data archive” : search for data returns null result : would you like to queue an observing request based on your search metadata?

  9. LOFAR data products will • be large … accurate and standardised metadata will reduce unnecessary downloads and processing • be heavily qualified … pointers into a global data model will help software and astronomers make valid use of the data • LOFAR should make a substantial contribution to data modeling in the VO • experience widely varying usage patterns … VO and Grid will provide intelligent caching and data distribution mechanisms

  10. adopting VO buys: • functionality: new and emerging VO tools and services, plus “wrapped” legacy software, immediately available • interoperability: all VO tools and services work with and understand LOFAR data to the best of their ability • archive & data centre: “reference” implementations of standards will provide “data centre in a box” software • wider user community

  11. Reality… • VO standards are moving targets • VOTable stores metadata and small catalogues; most “real” data still stored in legacy formats (FITS, HDF, …) • Tools implementing or supporting VO standards are rare! • Portals, workflows, embracing the Grid paradigm, …, are all in the future

  12. end ( unless you care about LOFAR data rates … )

  13. LOFAR data:baseband input & output • total baseband data rate is ~20 Terabits/s • 13000 antennae, dual pol • 64 Msamples/s • 12-bit sampling • total station data rate is ~150 Gigabits/s • 100 stations • 16 beams • 4 Msamples/s (2 MHz bandwidth) • 6-bit sampling

  14. LOFAR data:correlator input & output • central correlator input rate is ~150 Gigabit/s • output rate is ~10 GB per cycle • 5000 baselines (100 stations) • 2000 channels (2 MHz bandwidth, 1kHz resolution) • 16 beams • 4 polarisation products • 32-bit IEEE floats • ~36 TB/hr for 1s samples • ~3.6 TB/hr for 10s samples

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