4 The main CDS services

Figure 1: The main CDS on-line services

Figure 2: CDS home page on the World-Wide Web

A diagram of the main CDS services is shown in Fig. 1, and their list is given in the CDS Home Page (Fig. 2).

The first two main products of CDS have been the collection of information about astronomical objects from published papers and reference catalogues in SIMBAD, and the collection, documentation, long term storage and distribution of catalogues in the catalogue service, with the recent addition of the catalogue browser functionality of the VIZIER service. More recently, the ALADIN project has permitted us to construct an image server, and a comprehensive tool to overlay the information from SIMBAD, VIZIER, and from other sources such as NED or data archives, on digitized images of the sky. These services are described in companion papers (Wenger et al. [2000a]; Ochsenbein et al. [2000]; Bonnarel et al. [2000]).

The CDS also has the responsibility of the Dictionary of Nomenclature (Lortet et al. [1994]), hosts bibliographical information, with mirror copies of the ADS and of the Astrophysical Journal, the Astronomical Journal, and the Publications of the Astronomical Society of the Pacific, and develops bibliographic information retrieval tools (Poinçot et al. [1998]). It maintains the AstroGLU information discovery tool (Egret et al. [1998]), and hosts two Yellow Page services: AstroWeb (Jackson et al. [1995]), and the Star*s Family of Astronomy and Related Resources (Heck [1997]). CDS is the French IUE National host, the host of a copy of the CFHT user documentation and of the unpublished data on variable stars of IAU Commission 27.

The main evolution of the CDS in recent years, is the rapid development of the World Wide Web access to the services. Before 1996, the only CDS service available on the Web, besides documentation, was the access to the catalogues and tables (via ftp) and to the on-line abstracts of the journal Astronomy and Astrophysics. VIZIER was released in February 1996, the first Web version of SIMBAD in November 1996, and the Web access to ALADIN in November 1998 (Previewer) and February 1999 ( ALADIN Java). Now all the services are accessible from the CDS Home Page (Fig. 2).

The usage of the CDS services has been continuously increasing, with over 6 000 queries submitted to the CDS services and their mirror copies every day, and over 25 000 hits per day on the Web pages (November 1999).