Optics requirements for x-ray astronomy and developments at the Marshall Space Flight Center

X-ray optics have revolutionized x-ray astronomy; the degree of background suppression that these afford has led to a tremendous increase in sensitivity. The current Chandra observatory has the same collecting area (similar to 10(3) cm(2)) as that of the non-imaging UHURU observatory, the first x-ray observatory which was launched in 1970, but has five orders of magnitude more sensitivity due to its focusing optics. In addition, its 0.5 '' angular resolution has revealed a wealth of structure in many cosmic x-ray sources. The Chandra observatory achieved its resolution by using relatively thick pieces of Zerodur glass, which were meticulously figured and polished to form the four-shell nested array. The resulting optical assembly weighed > 1000 kg, and cost approximately $0.5B. The challenge for future x-ray astronomy missions is to greatly increase the collecting area (by one or more orders of magnitude) while ultimately maintaining sub-arcsecond angular resolution, and all within realistic mass and budget constraints. Published by Elsevier B.V.