Astronaut John Grunsfeld, National Geographic Adventure

"Around NASA, he's known as "the Hubble Repairman." And last May, on his third visit to the orbiting space telescope, John Grunsfeld pulled off the repair to end all repairs. Working at zero gravity some 350 miles above the surface of the Earth, the astronaut restored sight to a half-blind Hubble--called the greatest scientific instrument ever invented--and ensured that it will continue to send back the stunning images and mind-boggling data that have transformed our understanding of the universe."