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The implementation of a X-ray mission with high imaging capabilities, similar to those achieved with Chandra (< 1
arcsec Half Energy Width, HEW), but with a much larger throughput is a very attractive perspective, even if challenging.
For such a mission the scientific opportunities, in particular for the study of the early Universe, would remain at the state
of the art for the next decades. At the beginning of the new millennium the XEUS mission has been proposed, with an
effective area of several m2 and an angular resolution better than 2 arcsec HEW. Unfortunately, after the initial study,
this mission was not implemented, mainly due to the costs and the low level of technology readiness. Currently the most
advanced proposal for such a kind of mission is the SMART-X project, led by CfA and involving several other US
Institutes. This project is based on adjustable segments of thin foil mirrors with piezo-electric actuators, aiming to
achieve an effective area < 2 m2 at 1 keV and an angular resolution better than 1 arcsec HEW. Another attractive
technology to realize an X-ray telescope with similar characteristics is being developed at NASA/Goddard. In this case
the mirrors are based on Si substrates that are super-polished and figured starting from a bulky Si ingot, from which they
are properly cut. Here we propose an alternative method based on precise direct grinding, figuring and polishing of thin
(a few mm) glass shells with innovative deterministic polishing methods. This is followed by a final correction via ion
figuring to obtain the desired accuracy in order to achieve the 1 arc sec HEW requirement. For this purpose, a temporary
stiffening structure is used to support the shell from the polishing operations up to its integration in the telescope
supporting structure. We will present the technological process under development, the results achieved so far and some
mission scenarios based on this kind of optics, aiming to achieve an effective area more than 10 times larger than
Chandra and an angular resolution of 1 arcsec HEW on axis and of a few arcsec off-axis across a large field of view (1
deg in diameter).
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