Science Driven arguments for a 10 sq.meter, 1 arcsecond X-ray Telescope
  X-ray astronomy needs to set bold, science driven goals for the next decade. Only with defined science goals can we know what to work on, and a funding agency appreciate the need for significant technology developments. To be a forefront science the scale of advance must be 2 decades of sensitivity per decade of time. To be stable to new discoveries these should be general, discovery space, goals.   A detailed consideration of science goals leads us to propose that a mirror collecting area of 10 sq.meters with arcsecond resolution, good field of view (>10 arcmin), and with high spectral resolution spectroscopy (R=1000-10,000) defines the proper goal. This is about 100 times AXAF, or 30 times XMM. This workshop has shown that this goal is only a reasonable stretch from existing concepts, and may be insufficiently bold.   An investment of roughly $10M/year for 5 years in X-ray optics technologies, comparable to NASA's investment in ASTRO-E or a SMEX, is needed, and would pay off hugely more than any small X-ray mission. 
Martin Elvis and Giuseppina Fabbiano (Harvard-Smithsonian Center for   Astrophysics)