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The Virtual Observatory in Germany and abroad

This report provides an overview of the Virtual Observatory (VO) in Germany and abroad, including its motivation, approach, standards, and examples/demos from GAVO and other national VOs. It discusses the challenges and promises of the VO, the need for standardization, and the role of the International Virtual Observatory Alliance (IVOA).

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The Virtual Observatory in Germany and abroad

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  1. The Virtual Observatoryin Germany and abroad A status report with examples/demos from GAVO and other national VOs

  2. Overview • The Virtual Observatory • Motivation • Approach • The IVOA • Standards • Examples, demos private demos are always possible ! • GAVO • Project • Results • Outlook • Theory in the VO: • The Millennium Simulation database

  3. Astronomical data sets are large, and getting larger (courtesy Alex Szalay) Simulations as well (courtesy Simon White)

  4. Most data is (or could be) online MPE (http://www.mpe.mpg.de/AstR/ ) Google (http://www.google.com/Top/Science/Astronomy/Data_Archives/)

  5. Opportunities • So, the Internet is (or could be) the world’s best telescope: • It has data on every part of the sky • In every measured spectral band: optical, x-ray, radio.. • As deep as the best instruments (2 years ago). • It is up when you are up • It’s a smart telescope: links objects and data to literature on them • It even contains truly virtual data (courtesy Alex Szalay)

  6. Problems • Data formats not uniform • Interfaces not uniform • Data sets very large • Data set far away (makes them larger) • How to find data of interest? • Computers have difficulty understanding web pages

  7. Promises (/hopes) of the VO. • To make results of astronomical research, more readily available to the community • data and applications • To facilitate their • communication, reuse, comparison, combination , checking

  8. How ? • Online availability of datasets and applications • Standardisation of • publication and discovery mechanisms • description/meta-data (FITS++) • selection mechanisms • form(at)s of transmitted data • data access protocols • Why standardisation?

  9. FIRST ROSAT GAIA 2MASS SDSS Babylonian confusion N x M

  10. Why standardisation

  11. FIRST ROSAT GAIA 2MASS SDSS We need a common language N + M

  12. Standardise on: • Discovery • Data description (“meta-data”) • Data formats • Protocols • (Web) Application Interfaces • Query language

  13. Why (standardised) protocols? • VO service oriented. • Data sets too large to move : • You can FTP 1 MB in 1 sec (optimistically) • You can FTP 1 GB in min (= 1 $/GB) • You can FTP 1 TB in 2 days and 1K$ • You can FTP 1 PB in 3 years and 1M$ (numbers from Alex Szalay) • SFTP even slower • Remote filtering required to reduce size data sets • “Move analysis to data”: services • Allow programmatic access to services

  14. SSA SCS SIA VO’s esperanto

  15. Warning • VO can not (and does not aim to) be everything to everyone • Users will have to be able to visit the underlying data in all gory detail: provenance • Even then standardisation helps • Agreement is hard to come by (see FITS) • Problems are hard ! • VO is still partially a research project.

  16. The International Virtual Observatory Alliance (IVOA) Facilitate the international coordination and collaboration necessary for the development and deployment of the tools, systems and organizational structures necessary to enable the international utilization of astronomical archives as an integrated and interoperating virtual observatory.

  17. Alliance of national VOs

  18. Working and Interest Groups • WGs • Standards and Process: how the IVOA works • Resource registry: where to register and discover resources • Data Modeling: how to describe data sets • Semantics: how to understand one another • VOTable: standard format for tabular data sets • Data Access Layer: very simple data access services • VO Query Language: more sophisticated data access • Grid and web services: programmatic accessibility • Applications: stand alone, and together • VOEvent: astronomical telegrams in XML • IGs • Theory: virtual observations for virtual universes • Open GridForum Astro-RG: VObs and virtual organisations • Data Curation and Preservation: how not to loose your data

  19. Publication standard:Resource Registry • Implementations: • Searchable Registry at STScI • NCSA Publishing Registry • ESAVO Full Registry • Client tools: • VOExplorer (AstroGrid) • Splat, SpecView, Aladin

  20. Messaging standard: VOTable • http://www.ivoa.net/twiki/bin/view/IVOA/IvoaVOTable • XML format for tabular data • Column definitions included with data • Binary streams and FITS included • Understood by many client tools (see applications set) • TOPCAT • VOPlot • Aladin • Many others

  21. VOTable example

  22. Data Access Protocols I • Simple protocols for discovering and retrieving data sets • Generally HTP-GET based: • Base url: http://www.g-vo.org/ssa?action=doQuery&archiveid=ssa.service.cdfs • Query parameters:POS=53.161,-27.832&SIZE=0.2&BAND=0/&TIME=,&FORMAT=ALL • Returns (heavily) annotated list of spectra with access URL for retrieving them.

  23. Data Access Protocols II • Examples from GAVO, for more usage examples see tool demos • Simple cone search (source catalogues) • ROSAT source catalogues and photon event lists) • Simple Image Access • ROSAT pointed observations and All-Sky Survey fields • Simple Spectral Access • Chandra Deep Field South optical follow up

  24. Registry + DAL protocols:Interoperability Standard services, once registered, can be found by client tools …

  25. Interoperability ….and executed together (too many ROSAT results to show all here!)

  26. Interoperability … and shown together

  27. Applications, tools • VO aware tools: • Images: Aladin • Source lists and tables: TOPCAT, VOPlot • Spectra: Splat, SpecView, VOSpec • 3D: VisIVO • Application interoperability: Plastic • Messaging standard • Tying TOPCAT to Aladin to Splat to … • Uses VOTable to send data from one app to another • All on your desktop

  28. GAVO

  29. GAVO: VO in Germany • BMBF funded • In 2nd phase of financing • Institutes/people • AIP: M. Steinmetz (Co-I), I. Nickelt • ARI-ZAH: PI J. Wambsganss (PI), M. Demleitner, U. Stampa • MPE: W. Voges (Co-I), J.Kim, G.Lemson • Uni Tϋbingen: T. Rauch • TUM-Informatik: B. Gufler

  30. GAVO tasks • Investigate archiving and IVOA compatible publication • Investigate data mining techniques • Participate in -, and represent IVOA efforts • Special emphasis on theory in the VO • GAVO-expertise center and archive @ARI • Support for custom services • Info/help on all things VO for Germany (Please come by !)

  31. GAVO services, standard and custom • SCS and SIAP for ROSAT results (J.Zuther) • Cross matcher tool (used by S. Komossa) • SSA for CDFS spectra (G. Szokoly) • Publication A. Finoguenov’s A3266 data. • SSA for TMAP synthetic spectra (T. Rauch, Tubingen) • Various virtual telescopes (Planck@MPA, K.Dolag, J. Blaizot) • RASS source classifier (Class-X team) • Cluster finder (P. Schuecker et al) • Now in AstroGrid-D (A. Carlson)

  32. GAVO current and planned projects • GAVO@ARI • Archive for small science results • Feedback on all things GAVO • Hopefully long term • Collaborative tool • Automated upload and annotation of data • Wrap with IVOA protocols • Pre-publication collaboration capabilities • Simulation registry

  33. Theory in the VO

  34. Observations in the VO • Most VO efforts concentrate on observational data sets • simple observables: photons detected at a certain time from a certain area on the sky • long history of archiving • pre-existing standards (FITS) • valuable over long time (digitising 80 yr old plates) • Standards observationally biased • common sky: cone search, SIAP, region • common objects: XMatch • data models: characterisation of sky/time/energy(/no polarisation yet)

  35. Theory in the VO: issues • Simulations not so simple • complex observables • no standardisation (not even HDF5) • archiving ad hoc, for local use • Moore’s law makes useful lifetime relatively short: few years later can do better • Current IVOA standards somewhat irrelevant • no common sky • no common objects • requires data models for content, physics, code

  36. The Millennium database + web server • Post-processing results only • SQLServer database • Web application • portal: http://www.mpa-garching.mpg.de/millennium/ • public DB access: http://www.g-vo.org/Millennium • private access: http://www.g-vo.org/MyMillennium • Access methods • browser with plotting capabilities through VOPlot applet • wget + IDL or R • TOPCAT plugin

  37. Usage statistics

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