The mirror system of the X-ray satellite
ROSAT has been formed and
polished from a glas ceramic material by the
Carl Zeiss company, Oberkochen.
X-ray astronomy makes great demands on the accuracy of surfaces:
the X-ray mirror of almost ten square meter polished surface shows
an average residual roughness of only a few atomic diameters - at the
construction time of ROSAT this was the smoothest surface ever
manufactured. Correspondingly large was the effort to prove the mirror
quality. The Max-Planck-Institut has built a 130 meter
long vaccum facility for the purpose of surveying mirrors of X-ray
Look at the entrance aperture of the ROSAT telescope. Four
parabolic-hyperbolic mirror pairs fitted into each other form a
Wolter Type-I Telescope with a focal length of 2.4 m, of which
ring segments - divided by 16 radial struts - are seen. Each mirror is
50 cm in length and the diameter of the largest mirror
is 84 cm. With it, ROSAT carries the largest X-ray telescope ever
built. Its mirror surfaces have a residual roughness of less than
3 Å, which make them, after a final polishing, the smoothest
mirrors ever produced for a grazing-angle telescope.
The scientific success of the ROSAT Mission is greatly based
on the extensive, carefully performed test and calibration phases.
The development of the X-ray mirrors was propelled by measurements in MPE's
PANTER test facility
situated on the campus of the Pantolsky
company at Neuried. This facility was also used for the ten-month
continual calibration of the ROSAT telescope. The aerial photograph
of the Bavaria Luftbildverlags GmbH at Eching near Munich in Germany
shows the facility after reconstruction for the XMM mission, the second
cornerstone of the Horizon 2000 programme of ESA. The 130 m long
X-ray test line can be seen at the lower edge of the picture.
Integration of the ROSAT X-Ray mirror at the Carl Zeiss company