Adaptive optics is far too complex to summarize in a HN comment: http://en.wikipedia.org/wiki/Adaptive_optics http://en.wikipedia.org/wiki/Adaptive_optics Hubb

Adaptive optics is far too complex to summarize in a HN comment: http://en.wikipedia.org/wiki/Adaptive_optics http://en.wikipedia.org/wiki/Adaptive_optics Hubble is of the best spy satellites. It was built by the same team that builds spy satellites, using all the same parts and equipment, tested in the same facilities, etc. It just has a slightly different secondary mirror setup and a very different set of instruments and control mechanisms, since it's meant to point at galaxies and do astronomy, not at the Earth doing surveillance. Seriously, one of the hardest parts of the Hubble program was figuring out how to do it in the view of the public without revealing the underlying surveillance programme.