AIDA WP7_T7_RadioCubes

Bonnarel, Harrison, Richards (coordinator), Rixon

This is a strawoman draft to get the ball rolling...

Definition

In broad terms, a data cube can be used to mean any data with >2 axes and multiple points on at least 3 of those axes. Some common varieties for radio data (which may originate from interferometric observations, single-dish mosaics, or simulations) are:

  1. Right Ascension, Declination, Frequency
    • Frequency may be replaced by Velocity or the data may contain a method for interconversions. This can be complicated if there are spectral lines with different rest frequencies in the cube.
  2. Right Ascension, Declination, Stokes (polarization type).
  3. Right Ascension, Declination, Time.
Even these axes may not be in this order. The axes may not be uniformly sampled, e.g. a cube may consist of multple continuum frequencies at arbitrary spacings, each with a different sub-bandwidth. Some data (especially at higher frequencies) may be in wavelength rather than frequency units. The positional axes are often in Galactic or other coordinates. Healpix is a special case, where one axis represents 2 (or is that 3?) spatial dimensions. Varieties 2. and 3. will be easier to model once the Polarization and Time standards are more mature. Visibility data could be called a data cube, but this is also a separate ongoing IVOA modelling effort, although all of these, including this effort, should fit the recognised IVOA standards, in particular the Characterisation data model. We should be consistent as far as possible with other specific 3D data model implementations, if any (Chilingarian IFU model?). In this Workpackage, we start by considering image data cubes; the eventual scope can be determined in response to feedback. We should start with the cases most in demand; if we keep our model conistent with IVOA standards it should be extensible. The model should be aimed at allowing identifyable users to access available data, rather than trying to be all-encompassing from the start.

Preparation

  1. Look for use cases from astronomer end users
    1. Finding and retrieving suitable data
    2. Sending data to suitable tools and services
    3. Planning observations
    4. Publishing their own data
  2. Establish current and planned availability of data cubes, their state eith respect to metadata, science-readiness, publication mechanisms etc.
    1. Radio facilities with a European interest (present or near-future, including simulators) - the DCA Census should help here;
    2. World-wide archives and data associated with publications
  3. Investigate whether there are any relevant VO-enabled tools or services and if so, what metadata they require from a data cube model.

Draft model

  1. Textual description
  2. UML
  3. XML

Test model

-- AnitaRichards - 11 Mar 2009


This topic: EuroVOAIDA > WebHome > WP7DALDM > AidaWp7T7 > InitialThoughts
Topic revision: r1 - 11 Mar 2009 - AnitaRichards
 
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