Nontraditional grazing incidence optics for x-ray astronomy

All focussing x-ray telescopes that have been in orbit (Einstein, EXOSAT, and ROSAT) or are currently being developed (e.g., ASTRO-D, SAX, AXAF, and XMM) are based upon the same type of optics, the Wolter Type I system or a conical approximation of it. With funding, weight, and volume now being severely limited, new investigations in x-ray astronomy will have to specialize on a particular study, e.g., wide field surveys, spectroscopy, broad band measurements, and should have significantly more capability than the current missions in that study. Several novel approaches to broad band and wide field optics have been described in the literature that may be able to satisfy certain specific objectives better than the Wolter I.