XMM-Newton Home
Repository of XMM-Newton EPIC Filter Wheel Closed (FWC) Data.

Due to a planned migration of the XMM-Newton SOC web portal, all SOC internet services (including ToO Alerts) will be unavailable Wednesday, 10 February from 10:00 to 13:00 (GMT).

The EPIC CCD cameras on board XMM-Newton are equipped with a filter wheel system and 6 different filter setups, seperated by angular distance of 60 degrees. These are:
  • Closed (1.05 mm Al)
  • Thin1 (40 nm Al + 160 nm polyimide)
  • Thin2 (40 nm Al + 160 nm polyimide)
  • Medium (80 nm Al + 160 nm polyimide)
  • Thick (45 nm Sn + 55 nm Al + 330 nm polypropylene + 55 nm Al)
  • Open
The individual layers are given from the telescope toward the detector. By turning the filter wheel from any of the abovementioned positions by a few degrees a radioactive Fe-55 source (decay into an excited state of Mn) can (additionally) illuminate the CCD (Cal positions, e.g. CalClosed, CalThin1).

These exposures are dominated by the instrumental background and can be used to model and subtract the internal instrumental background. This is composed by:

  • electronic readout noise (at lowest energies)
  • high energy particles producing charge directly in CCD and Camex
  • Particle induced X-rays (continuum and fluorescent lines), generated inside the camera
  • thermal CCD noise is negliglible

In the following links, further information is provided on camera-specific issues related to FWC exposures, including links to the corresponding merged collection of FWC data. FWC data are available for the EPIC-MOS and EPIC-pn cameras.

A complete description of the EPIC background can be found at:

Contact: For any questions contact the XMM-Newton Helpdesk through the following page:

Last update: 2015-05-13

XMM-Newton; Europe's X-Ray Observatory
Last update: 20-May-2015 by