This section of the webpage uses javascript. Please enable javascript in your current browser or choose a browser that supports javascript.
XMM-Newton Education and Public Outreach
Sonoma State University Education and Public Outreach Goddard Space Flight Center Sonoma State University Education and Public Outreach

Reflection Grating Spectrometer

A reflection grating spectrometer works in a very similar way as an optical prism does, by spreading out the incoming light according to the wavelength of the photon. In fact, in the case of XMM, the reflection gratings are nothing more than mirrors with tiny grooves on them. The mirrors are covered with a gold layer, and there are 600 grooves per millimeter: so thin that one single human hair would cover 15 of them! Once dispersed out into a spectrum, the X-rays are focused on the two RGS cameras. These cameras share the telescope focusing plane with the EPIC cameras.

XMM-Newton Reflection Grating Array
A view of an XMM-Newton Reflection Grating Array, illuminated by optical light in the same way as X-ray light would enter in flight.

XMM-Newton is the first X-ray mission to fly a reflection grating. It can identify lines of elements like iron, oxygen, silicon, and magnesium, which are common in astrophysical plasmas. Many institutions participated in the construction of the RGSs: Mullard Space Science Laboratory (MSSL), the Paul Scherrer Institute (PSI) in Villigen (Switzerland), Space Research Organisation Netherlands (SRON), and Columbia University (New York USA).

More images of the RGS

If you have any questions concerning XMM-Newton send e-mail to


This page was last modified on (none).

Science Mission Directorate Universe Division
Beyond Einstein

  • Questions/Comments/Feedback
  • Find helper applications like Adobe Acrobat
  • Learn about black holes, astronomy & more!
  • A service of the Astrophysics Science Division at NASA/ GSFC

    XMM-Newton Project Scientist: Dr. Steve Snowden
    XMM-Newton Mission Scientist: Dr. Richard Mushotzky
    Responsible SSU Personnel: Lynn Cominsky
    Web Curator: David McCall
    Privacy, Security, Notices