It's arguably the most powerful scientific instrument ever created, adept at inspecting exploding stars and glimpsing billions of years back in time. Yet the Hubble Space Telescope is really just a giant orbiting lens, only as good as the camera within. This month, astronauts will deliver an even better internal eye, the Advanced Camera for Surveys. The upgrade will allow Hubble to operate 10 times more quickly. Here is a brief history of the telescope that changed the way we think about the universe.