In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes
with large aperture areas (≈ 3 m2) and fine angular resolution (≈ 12). Achieving such performance is programmatically
and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for
densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting,
and assembly of large areas (≈ 600 m2) of lightweight (≈ 2 kg/m2 areal density) high-quality mirrors, at an acceptable cost
(≈ 1 M$/m2 of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible
approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space
adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential
erosion or deposition, and coating-stress manipulation of thin substrates.
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