The seven-member crew of space shuttle Atlantis lifted off Monday for one of the riskiest shuttle flights yet — so risky, in fact, that another space shuttle is ready to launch in case they need to be rescued.
Atlantis launched at 2:01 p.m. EDT on one last maintenance mission to the Hubble Space Telescope, the 19-year-old orbiting observatory that floats at an altitude littered with space debris.
One good-sized chunk, traveling at thousands of miles per hour, could rip through the shuttle's hull, leading to fatal decompression.
The six men and one woman who will attempt the complicated job raised their fists as they headed out to the pad earlier Monday, eager to get going after waiting seven months to lift off.
Their flight was delayed last fall, two weeks before the scheduled launch, after a critical computer on Hubble crashed and had to be remotely rebooted.
"Let's go!" commander Scott Altman said. "Yeah!"
Atlantis should reach the Hubble Space Telescope Wednesday.
The Hubble scientists and managers were euphoric to finally be so close to liftoff.
"I'm feeling wistful because this is the final mission," said senior project scientist David Leckrone. "It's the end of the era of Hubble servicing."
Nearly 30,000 people were at Kennedy Space Center for the launch, including space-center workers and guests.
On this fifth and final repair mission, Atlantis' crew will replace Hubble's batteries and gyroscopes, install two new cameras and take a crack at fixing two broken science instruments, something never before attempted.
Those instruments, loaded with bolts and fasteners, were not designed to be tinkered with in space.
They also will remove the command and data-handling unit that failed in September and had to be revived, and put in a spare that was hustled into operation.
Fresh insulating covers will be added to the outside of the telescope, and a new fine guidance sensor for pointing will be hooked up.
Five spacewalks will be needed to accomplish everything. The work is so tricky and intricate that two of the repairmen are Hubble veterans, John Grunsfeld and Michael Massimino. Grunsfeld, the chief repairman, is making an unprecedented third trip to the telescope. Altman, the commander, also has previously flown to the telescope.
"We'll give it our best," Altman said.
The 11-day mission comes with a higher risk than usual.
Atlantis will be flying in an unusually high orbit for a space shuttle — 350 miles up. Space is more littered there, and the odds of a catastrophic strike are greater.
In addition, there's always the chance the shuttle could be damaged during liftoff by a piece of fuel-tank insulating foam or other debris, which doomed Columbia in 2003.
NASA canceled this last Hubble mission in 2004, saying it was too dangerous. It was reinstated two years later by the space agency's new boss, but only after shuttle flights had resumed and repair techniques had been developed.
As an added precaution, another shuttle was ordered to be on standby, in case Atlantis suffered irreparable damage.
Atlantis will be too high and too far from the International Space Station, the shuttle crews' normal place of refuge in case of emergency.
Endeavour, the rescue ship, is at NASA's other launch pad, ready to lift off within a week to save Atlantis' crew.
"There's a very slim chance that that plan will ever be put into play," former space shuttle astronaut Tom Jones told FoxNews. "I don't really think it's going to be necessary."
All told, it's a $1 billion mission. The space telescope, over the decades, represents a $10 billion investment.
It was launched amid considerable hoopla in 1990, but quickly found to be nearsighted because of a flawed mirror. Corrective lenses were installed in 1993 during what NASA's science mission chief, Ed Weiler, calls "the miracle in space mission."
"We have seven years of accumulated maintenance work to do," Hubble program manager Preston Burch said. "So you can imagine if you had a car and you were driving it every day for seven years and never took it into the shop. You would have quite a list of things to do on it."
With all the newest pieces, NASA hopes to keep Hubble churning out breathtaking views of the universe for another five to 10 years. The new cameras should enable the observatory to peer deeper into the cosmos and collect an unprecedented amount of data.
"I personally believe the stakes for science are very high," Leckrone said on the eve of the launch. "It's a very complex, very ambitious mission, and it makes the difference between an observatory that's kind of limping along scientifically and an observatory that's the best ever."
Because this is the final visit to Hubble, "we're going for broke," Leckrone told reporters.
The Associated Press contributed to this report.