ABC News has been given unprecedented access to the astronauts, scientists and engineers involved in the intensive — and some say risky — shuttle mission to repair the Hubble Space Telescope later this year.
Time is running out for Hubble. If its batteries and gyroscopes aren't replaced soon, the most famous of space telescopes will simply quit functioning.
If all goes well, the Space Shuttle Atlantis mission, dubbed STS 125, will launch in August to service Hubble. ABC News will follow the crew as it trains for this mission.
This will be the last time a space shuttle visits Hubble. Everyone involved knows they must make every single minute of the mission count to ensure Hubble will continue to explore the universe until the replacement Webb telescope can be launched sometime in the next decade.
What makes this mission risky?
Unlike most recent shuttle missions, this one will not be docking at the International Space Station. If Atlantis encounters an emergency, Hubble's orbit is so far from the space station, that the Atlantis crew will not be able to reach it.
But NASA is ready with an unprecedented backup plan. For the first time, when the Atlantis astronauts launch to repair Hubble, a second shuttle will already be on the other launch pad at the Kennedy Space Center, ready to go within days if its colleagues on the Hubble mission encounter a problem.
It is easy to see why the Hubble mission is the most talked about mission of the year at NASA and overshadows the global effort to build the International Space Station.
Hubble is the telescope that can look back in time; the space station is still a construction project, albeit one of the most complicated ever undertaken.
Just what kind of allure does the Hubble Space Telescope have that the International Space Station doesn't? Apollo 7 astronaut Walt Cunningham says it's all about perception.
"The International Space Station is the most incredible engineering achievement in history. It exceeds the Panama Canal or the pyramids if you will, but it doesn't capture the public's fancy, because it looks like a truck driving back and forth delivering construction materials," he said.
Hubble was deployed in 1990, and it wasn't an instant hit. Its first images were blurry because of an embarrassing failure to notice that the shape of the telescope's primary mirror was not accurate.
A daring space shuttle mission to install corrective lenses fixed that in 1993. That troubled beginning is part of its mystique, according to Sandra Faber of the University of California at Santa Cruz.
"It was such a disaster, but it was like chestnuts pulled out of the fire at the last minute. It is the ultimate American can-do story," she said.
And oh what Hubble can do! Hubble has allowed scientists to estimate the age of the universe — 14 billion years.
Faber points to Hubble's discoveries about galaxies. "First and foremost for me as [a] student of galaxy formation, Hubble was the first telescope to look back in time and show us infant galaxies, in the process of being born. That's a first. To use a telescope as a time machine looking back billions of years — that is a terrific legacy."
Matt Mountain, director of the Hubble Space Telescope, says the telescope's popularity is simple to explain.
"It allows us to see the universe in a way we don't have to explain. A picture is worth 1,000 words and so we look back in time at some of the earliest galaxies," he said.