Foil X-ray mirrors

Nested thin foil reflectors have made possible light weight, inexpensive and fast grazing incidence X-ray mirrors for astronomical spectroscopy over a broad band. These mirrors were developed at Goddard for the US Shuttle program and were flown on NASA's shuttle-borne Astro-l mission in December 1990. Presently, the Japan/US collaborative spectroscopic mission ASCA, nearing it's third year of successful operation in earth orbit, carries four such mirrors, weighing less than 40 kg and giving total effective areas of similar to 1200 and 420 cm(2) at 1 and 8 keV respectively. The similar to 420 kg observatory is the best possible example of how conical foil mirrors opened areas of research that could not have been otherwise addressed with available resources. In this paper, we will briefly review the development and performance of our first generation foil mirrors. We will also describe progress toward improving their imaging capability to prime them for use in future instruments. Such a goal is highly desirable, if not necessary for this mirror technology to remain competitive for future applications.