The TIME 100

Both times I flew to the moon, I was struck by how comparatively quick the trip was—less than three days' transit. Then again, the moon is merely a quarter of a million miles or so away. Getting to know more remote bodies requires telescopes—exceedingly powerful ones. The most sophisticated telescope in history is currently being built by a NASA-led team. It's called the James Webb Space Telescope, and the mind behind it is astrophysicist and Nobel prizewinner John Mather. The Webb telescope, set for launch in 2013, will work mostly in the infrared spectrum, the wavelength in which many bodies emit their most revealing energy. And it won't be parked in a cozy Earth orbit but in a cosmic odd spot 1.5 million miles away where the gravity of the sun and Earth will hold it in a sort of suspended tension.

Mather, 60, the senior scientist guiding the Webb project, has been helping to develop similar NASA projects for more than 30 years, most notably the Cosmic Background Explorer (COBE). It was his analysis of COBE data that earned him the 2006 Nobel, which he shared with University of California cosmologist George Smoot. Astronauts know that having the right person commanding any mission is essential to its success. The same is true for scientists who never leave Earth.

Lovell, commander of Apollo 13, also flew on Apollo 8, Gemini 7 and Gemini 12