Several x-ray astronomy missions of the 1990s will contain focusing telescopes with significantly more collecting power than the Einstein Observatory. There is increasing emphasis on spectroscopy. ESA's XMM with 104 cm2 of effective area will be the largest. A high throughput facility with over 105 cm2 of effective area and 20-sec of arc angular resolution is needed ultimately for various scientific studies such as high resolution spectroscopic observations of QSOs. At least one of the following techniques currently being developed for fabricating x-ray telescopes including automated figuring of flats as parabolic reflectors, replication of cylindrical shells, and the alignment of thin lacquer-coated conical foils is likely to permit the construction of modular arrays of telescopes with the area and angular resolution required.
"High Throughput X-Ray Optics: An Overview", Proc. SPIE 0830, Grazing Incidence Optics for Astronomical and Laboratory Applications, (9 August 1988); doi: 10.1117/12.942172; https://doi.org/10.1117/12.942172