“…The figure error of <10 lm enables us to make a smooth surface using several methods, for example, by using a replication method (Furuzawa et al, 1998). We applied improvements of the ASCA type mirror to the new type mirror, because we have a good understanding of the characteristics of the ASCA type mirror (Tsusaka et al, 1994(Tsusaka et al, , 1995, and this type of mirror satisfies the weight constraints of Japanese satellites. The design of our prototype of the substrate is shown in Fig.…”