Each of the software components of the AVO prototype is developed and maintained by a different team in a different country. All modules work stand-alone, but can be integrated. The AVO prototype consists of a browser backed by image and catalogue servers, a web service for the identification of sources in FITS images and a utility for analyzing the spectral energy distribution.
The AVO is a research and demonstration programme jointly funded by the European Commission and six European organizations. The partner organizations are the European Southern Observatory (ESO), the European Space Agency (ESA), AstroGrid (funded by PPARC as part of the UK's E-Science programme), the CNRS-supported Centre de Données Astronomiques de Strasbourg (CDS), the University Louis Pasteur, the CNRS-supported TERAPIX astronomical data centre and the Jodrell Bank Observatory. The AVO project is working in conjunction with other international VO efforts as part of the International Virtual Observatory Alliance (IVOA).
The AVO prototype is a set of tools that initially consisted of three components (fig. 1, fig. 2):
Recently VO-India contributed the VOTable plotter VOPlot and further work continues, for instance, into a cross matching facility.
The various modules exchange information in UCD tagged VOTable format (fig. 3). Although often compared to the FITS format its scope is much wider and the format far more versatile. Uniform Content Descriptors (UCDs) are meta data to describe astronomical parameters. UCDs are arranged in a hierarchical tree. UCDs and extensions thereof will soon form the basis of a meta data standard for expressing meaning in astronomical terms in a system independent way.
At various occasions scientists demonstrated the unique capabilities of the toolset using a number of scientific scenarios such as the identification of super nova candidates, the investigation of the high redshift environment in the GOODS fields and the multi-waveband analysis of radio observations in the HDF-N and HFF.
Several colour catalogues provided by the ESO Imaging Survey (EIS), source catalogues from Chandra, ISO, VLA etc. in conjunction with images listed in tab. 1 helped in detecting peculiar objects.
The next round of demos will focus on adding support for spectroscopic data and opening the system to arbitrary data providers. This entails the specification and adaptation of the simple spectrum access (SSA) protocol. A geometric cross matching capability will be added. Various new scientific scenarios are driving the current development which will result in a new release in January 2004.