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THE XMM-NEWTON MIRRORS

    Schematic of the X-ray mirror geometry
    (From the XMM-Newton Science Operations Center.)

    Schematic of the X-ray mirrors
    (From the XMM-Newton Science Operations Center.)

    Mirrors for X-ray telescopes are built in a manner very different from those of optical telescopes, such as the Hubble Space Telescope. Instead of reflection angles near 180 degrees, X-ray mirrors only deflect the photons by a few degrees, as shown in the inset in the lower figure above (the upper figure shows an expanded view of the geometry). The combination of a reflection off the first paraboloid surface with a second reflection off the hyperboloid surface will focus the X-rays on the focal plane. This is the geometry of the Wolter Type I mirror system.

    Mirror Module Details
    Mirror Type Wolter Type 1
    Focal Length 7500 mm
    Outermost Mirror Radius 350 mm
    Innermost Mirror Radius 159 mm
    Axial Mirror Length (paraboloid + hyperboloid) 600 mm
    Outer Mirror Wall Thickness 1.07 mm
    Inner Mirror Wall Thickness 0.47 mm
    Minimum Packing Distance 3 mm
    Reflective Surface Gold
    Mirror Substrate Monolithic Nickel
    Number of Mirrors (paraboloid + hyperboloid) 58
    Mirror Module Mass 437 kg
    Angular Resolution, Half Energy Width 15 arc seconds, 0.1-10 keV
    Angular Resolution, Full Width Half Maximum <6 arc seconds, 0.1-10 keV
    From ESA Bulletin, Number 89, 1997 February.

    Schematic of the X-ray mirror geometry including the RGS gratings
    From the XMM-Newton Science Operations Center.

    The above figure shows the geometry for the RGS. The gratings of the Reflection Grating Assembly sit in the light paths between the mirrors and the EPIC MOS cameras. They deflect about 40% of the light to the RGS Focal Cameras and allow about 42% of the light to continue on to EPIC. The rest of the light is absorbed by the support structures.

If you have any questions concerning XMM-Newton send email to xmmhelp@athena.gsfc.nasa.gov