WP-A5.1: Optical/Near-IR pilot - Large Object Catalogues

(WPM: Mann - Staff: Mann, 0.10 FTE; Davenhall, 0.10 FTE; McMahon, 0.05 FTE)

This pilot addresses the practical problems of federating large object catalogues, through two methods. Firstly, data from the SuperCOSMOS Sky Survey (SSS) covering the fields of the Sloan Digital Sky Survey (SDSS) Early Data Release (EDR) will be federated with the EDR data themselves, using a version of the SDSS science archive software (called SX), modified for use with the SSS data model. Secondly, catalogues of objects derived from INT imaging with the Wide Field Camera (optical) and CIRSI (near-infrared) will be federated by making them both accessible via the VizieR system developed by the Centre de Données astronomiques de Strasbourg. The functionality provided by the two approaches will be compared by providing access to both federations to test users, who can assess how well they each match the needs of scientists using future federations of large object catalogues in the VO: further assessment of the suitability of the VizieR will come from its use within the deployment of an interoperability test bed as part of AVO Work Area 2 (Interoperability).

Example Science Cases:

A scientist wishes to search for halo white dwarf stars, which requires selection criteria making use of both colour and proper motion information for a large sample of stars (for these are rare objects). This can be achieved by querying the multi-epoch/multi-colour dataset produced by federating the Sloan EDR dataset with the SuperCOSMOS Sky Survey coverage of the same region.

A scientist wants to determine the optical and infrared colours of an object, e.g. an X-ray (XMM) or radio (FIRST) or far infrared (ISO) source. This can be achieved by querying the multi-colour dataset produced by federating the INT WFC five colour optical dataset with the 2 colour INT CIRSI dataset of the same region.


  • To produce working federations of two pairs of datasets: the Sloan EDR and SuperCOSMOS Sky Survey, using SX; and INT WFC and CIRSI data using VizieR.
  • To compare the suitability of the two approaches for performing the sort of complex, multi-parameter searches which VO users will want to perform on large object catalogues in the future.


  • A copy of the Early Data Release (EDR) database of the Sloan Digital Sky Survey (SDSS).
  • The SuperCOSMOS Sky Survey (SSS) database.
  • Object catalogues from the INT-WFC and INT-CIRSI.
  • The VizieR and SX archive systems.


  • Large object catalogue federation test bed.
  • Feedback on prototype system from test users.
  • Inputs of requirements to WP-A1.
  • Inputs of implementation issues to WP-A2, WP-A3, WP-A4 and WP-A9.
  • Inputs to the development of the Phase B plan.


  • 5.1.0 Design and requirements
    • Decide exactly which datasets to use in the pilot.

  • 5.1.1 Obtain data needed for pilot federation in desired format
    • Install a copy of the EDR dataset at Edinburgh.
    • Make the INT data from Cambridge accessible through Vizier.

  • 5.1.2 Determine what changes must be made to SX for the SSS implementation
    • Identify all schema-dependent code within the SX system.
    • Design a new schema for the SX implementation of the SSS.

  • 5.1.3 Implement modifications to SX
    • Produce a version of the SX system which serves the SSS data.

  • 5.1.4 Provide UI for SSS-SX
    • Modify the sdssQT query tool supplied with SX, as required for the SSS implementation.

  • 5.1.5 Evaluation of test bed implementations
    • Allow test users to compare functionality provided by two approaches to federation.
    • Gather inputs from developers and users.
    • Produce a technical note on the lessons learnt.
    • Provide inputs to the Phase B plan.

-- BobMann - 26 Feb 2002

Topic revision: r1 - 2002-02-26 - 14:59:00 - BobMann
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