ESO introduced a User Portal for its scientific services in November 2007. Registered users have a central entry point for
the Observatory's offerings, the extent of which depends on the users' roles - see . The project faced and overcame a
number of challenging hurdles between inception and deployment, and ESO learned a number of useful lessons along the
way. The most significant challenges were not only technical in nature; organization and coordination issues took a
significant toll as well. We also indicate the project's roadmap for the future.
Interoperability in Virtual Observatories is based on standards for interchange formats, and protocols. Using real science cases, we present example VO tools based on the AVO prototypes and the CDS services, which implement the new and emerging VO standards. We discuss how these standards, such as VOTable, UCDs and data models
enable interoperability between software components, and provide efficient and flexible means for data access. We show how UCDs are used in catalogue filtering and selection of relevant columns. We also demonstrate a simple yet powerful method for accessing data from image archives, customized data sets and local data within a single environment.
The goal of the Simple Spectral Access (SSA) specification is to define a uniform interface to spectral data including spectral energy distributions (SEDs), 1D spectra, and time series data. In contrast to 2D images, spectra are stored in a wide variety of formats and there is no widely used standard in astronomy for representing spectral data, hence part of the challenge of specifying SSA was defining a general spectrophotometric data model as well as definitions of standard serializations in a variety of data formats including XML and FITS. Access is provided to both atlas (pre-computed) data and to virtual data which is computed on demand. The term simple in Simple Spectrum Access refers to the design goal of simplicity in both implementing spectral data services and in retrieving spectroscopic data from distributed data collections. SSA is a product of the data access layer (DAL) working group of the International Virtual Observatory Alliance (IVOA). The requirements were derived from a survey among spectral data providers and data consumers and were further refined in a broad discussion in meetings and electronic forums as well as by prototyping efforts within the European Astrophysical Virtual Observatory (AVO) and the US National Virtual Observatory (NVO).
The joint archive facility of the European Southern Observatory (ESO) and the Space Telescope - European Coordinating Facility (ST-ECF) is undertaking particular efforts in the field of associating (grouping) Hubble Space Telescope (HST) observations for a number of years already. By now their users are given means for browsing associations of HST images. Soon the same capability will be provided for spectra as well. Associations of observations can either be defined and driven by requirements imposed by higher level algorithms like co-adding and drizzling techniques or by user defined constraints. In any case we consider these services an important precursor and testbed to a future virtual observatory. Two components complement an on-line interface (archive.eso.org) to such data products: For one part it is the selection process which can be greatly improved by adding preview capabilities for individual or multiple exposures. On the other hand it requires a request handling system which supports the concept of associations and which can expand a given association and computes and delivers calibrated and combined data products.