As for all space missions, the limit imposed on the payload mass budget by the launcher is the main driver that forces the
use of very lightweight optics. Considering the International X-ray Observatory (IXO) mission the present configuration
has a mirror collecting area in the order of 3 m2 at 1.25 keV, 0.65 m2 at 6 keV, and 150 cm2 at 30 keV. These large
collecting areas could be obtained with a mirror assembly composed of a large number of high quality glass segments
each being able to deliver the required angular resolution better or equal to 5 arcsec. These segments will form a X-Ray
Optical Unit (XOU), an optical subunit of the telescope, and the XOUs will be assembled to form the whole mirror
system. Based on the INAF-OAB experience in the thermal slumping of thin glass optics, a possible approach for the
realization of large size and lightweight X-ray mirrors is described in this paper.
Moulds made in a suitable material (as for example Silicon Carbide or Fused Silica) and having the suitable (parabolic
and hyperbolic) profile are used for the realization of thin glass Mirror Plates (MP), with dimensions in the range of 200-
400 mm. After a thermal cycle the slumped MPs are characterized for acceptation and handled by means of an active
support using vacuum suction for the integration phase. In this phase an active optical feedback is used to ensure the
correct alignment of the MPs within the XOU. The MPs are then glued in its proper position in the XOU using also
suitable glass ribs for the stiffening of the whole module.
An investigation in the problems and possible solutions to the slumping, measurement, integration and testing of the
glass MPs into the XOU will be given, particularly with respect to a XOU scaled prototype that will be manufactured
and used to assess the technology.