The Colossus telescope is also a nice proposal that fits in the $1bn pricetag, if its proponents are to be believed: http://the-colossus.com/technology.html ht

The Colossus telescope is also a nice proposal that fits in the $1bn pricetag, if its proponents are to be believed: http://the-colossus.com/technology.html http://the-colossus.com/technology.html Basically, a 74m telescope made of independent 8m mirrors, with a very narrow field of view (a few arcseconds), dedicated to extrasolar planets and other small FoV astronomical science.