The XMM-Newton SSC Database: Taking Advantage of a Full Object Data Model

One of the main responsibilities of the Science Survey Centre (SSC) of the XMM-Newton satellite, an X-ray observatory launched by the European Space Agency in 1999, is to carry out a systematic analysis of the entire scientific data stream. Products resulting from the pipeline processing are shipped to the guest observer and eventually enter the XMM-Newton archive. In addition, the SSC compiles a catalogue of X-Ray sources and provides an identification for ∼ 50, 000 new sources detected each year. In order to check product quality and to support the catalogue and source identification programmes, all SSC-generated products are stored in a database developed for that purpose. Because of the large number of transversal links, our data model was difficult to map into relational tables. It has therefore been designed with object oriented technology for both user interface and data repository, and based on an object-oriented DBMS called O2. The database is a powerful tool to browse and evaluate XMM-Newton data and to perform various kinds of scientific analysis. It provides on-line data views including relevant links between products and correlated entries extracted from many archival catalogues and also links to external databases. Besides browsing, the web-based user interface provides facilities to select data collections with any constraints on any keywords but also with constraints on correlated data patterns. 1. Database Overview The SSC database contains all data products resulting from the pipeline processing of the photon-event lists and other raw data from the XMM-Newton spacecraft. The products from a typical observation include ∼100 FITS files and ∼400 other files (HTML, PDF, etc.), and occupy ∼400MB. These data files are grouped by observations and contain both observational data (graphical products, tables, spectra, images and event lists) as well as extractions from astronomical archival catalogues generated by the cross-correlation (ACDS) with the archives at NED and at CDS in Strasbourg. They also include the catalogue