A Short Guide to XMM-Newton Science Data Products

The XMM-Newton Science Archive (XSA) is the repository of the XMM-Newton science data. A graphic user interface allows the XSA user to browse the archive, visualize quick-look products, and select files to be included in a "shopping basket" for subsequent retrieval. The XSA contains therefore all the XMM-Newton science files, as well as all the files which are necessary for a proper understanding, reduction and analysis of the XMM-Newton data, including interactive analysis tools, cross-correlations with other catalogues, etc. The scientific data contained in the XSA falls in one of the following categories:

• the Observation/Slew Data Files (ODF/SDF)
• the Processing Pipeline System (PPS) products
• the Current Calibration Files (CCF)
• the EPIC source catalogue
• the OM source catalogue
• the Slew Survey source catalogue
  

A brief description of these files is given hereinafter.

The user is invited to consult the specific documentation available on-line for a more complete description. General information about the mission is contained in the XMM-Newton Users' Handbook.

The ODF/SDFs

XMM-Newton reformatted telemetry is organized in the Observation/Slew Data Files (ODF/SDF). Most of the ODF/SDF files have a FITS format. ODF/SDFs contain uncalibrated science files, which cannot be directly used for scientific data analysis. Their content is described in the XMM-Newton Data Files Handbook and (more technically) in the XMM-Newton ODF/SDF Interface Control Document. ODF are ingested in the XSA about three weeks after an observation has been performed. In order to create scientifically usable and calibrated products, SAS reduction tasks must be run on the ODF/SDFs.

The PPS products

The scientific analysis of XMM-Newton data can be started from the products created by the pipeline processing, which are also described in the XMM-Newton Data Files Handbook. All the pipeline (PPS) products are available in the XSA. The processing employs standard SAS tasks and modules. The aim of the pipeline processing is to provide a set of data products which will be of immediate value for the XMM-Newton observer. The XMM-Newton pipeline products include calibrated, "cleaned" event lists, as well as a number of secondary high-level products such as sky images, source lists, cross-correlations with archival catalogues, source spectra and time series. The responsibility of the pipeline processing lies with the Science Survey Centre (SSC). Each dataset processed is subject to a screening process by the SSC team which aims at verifying the quality of the processing and the identification of any processing problems. Reports, describing the quality of the PPS outcomes, are linked in the XSA to the corresponding observations. Within the XSA, individual PPS products can be individually retrieved. Several FITS-format or graphical products can be directly viewed through the XSA graphic interface.

A general description of the data products for each pipeline version can be found in the corresponding Documentation and PPS release notes. The structure of the PPS files is defined in the XMM SSC to SOC interface control document for SSC data products. A detailed description of the individual files can be found in the Specifications for individual SSC data products.

The CCF constituents

All the XMM-Newton calibration data are organized in a "Current Calibration File" (CCF). Each constituent of the CCF is uniquely identified by its issue number and date of validity. Access to the CCF is based on the Calibration Index File (CIF), which must be generated by the user through a specific SAS task at the beginning of an analysis session. A CIF is defined by the observation date, and by the analysis date. A functionality is available into the XSA to produce a CIF file, corresponding to each observation for each possible analysis date.

CCF constituents are available from the XMM-Newton Calibration Page. This directory is frequently updated. The user is referred to the XMM-Newton Calibration Access and Data Handbook (available on the Calibration Documentation Page) for more information about the calibration files, and the SAS infrastructure to access/visualize the content of the CCF constituents (Calibration Access Layer, CAL). The CCF release notes provide information on the accuracy of the XMM-Newton calibrations.

The SAS

The Science Analysis System (SAS) is the software package to reduce and analyze all XMM-Newton data. Users are invited to consult the on-line available documentation. A set of data has been defined, to test the performances of each new SAS release, both in terms of functional support for all the XMM-Newton instrument modes and with respect to the quality of the current XMM-Newton calibration. These data are available at the SAS Science Validation Page, where users will also find the SAS Science Validation Report.


Send your questions about the XSA to the: XMM-Newton HelpDesk