In this photo provided by NASA, astronaut Mike Massimino works with the Hubble Space Telescope in the cargo bay of the Earth-orbiting space shuttle Atlantis.
Astronauts wrapped up work on the interior of the Hubble space telescope with a notable absence of glitches and closed the observatory's doors for good, setting the stage for another decade of even more brilliant photos of mysterious corners of the universe.
After the first four spacewalks generated a host of time-consuming glitches, the Atlantis crew was pleased make steady progress on its final day of scheduled repairs to the Hubble Space Telescope, beginning work nearly an hour early.
"This is a great day, a great way to finish this out," Mission Control told the spacewalkers.
Spacewalkers John Grunsfeld and Andrew Feustel left the space shuttle Atlantis Monday morning well before their 9:16 a.m. eastern time scheduled start to replace three more batteries, a sensor and some insulation. Some of today's repairs were supposed to be completed Sunday, but couldn't get done because of problems with a balky bolt that caused all sorts of problems.
By early afternoon, all of the work had been completed, including installation of the steel sheets will protect the telescope from radiation and extreme temperature changes.
The four astronauts working in pairs have earned rave reviews for dealing on the fly with contingencies. Working 350 miles above the earth, they used brute force to loosen and even snap off stuck bolts, resorted to a refurbished gyroscope when the new one did not fit and dealt with an assortment of minor malfunctions. In all, they outfitted the observatory with $220 million in upgrades that should allow the telescope to look back to within 500 million years of the dawn of time.
The shuttle will release Hubble on Tuesday. NASA hopes these repairs will buy Hubble five to 10 more years of life. After that, a robot will steer Hubble back into Earth's atmosphere, with the observatory's camera eventually being displayed at the Smithsonian.
On Sunday, it was a stripped bolt that flummoxed the spacewalkers. When several tries with different expensive tools couldn't remove a stripped-out bolt, Mission Control in Houston told Massimino to go for the less precise yank.
At Goddard Space Flight Center in Maryland, engineers twice tested that pull on a mock-up before Massimino was told to use his muscles.
"You hope you don't get to the point where you just close your eyes and pull and hope nothing happens," said James Cooper, the Goddard mechanical systems manager for the repair mission. "But we had run out of other options."
Astronauts were careful to tape pieces so they wouldn't fly away and become potential missiles.
One last task marked the end of the mission: Giving the telescope, beloved by earth-bound science enthusiasts, a hug on behalf of "thousands and thousands of Hubble huggers all over the world," said Senior Project Scientist David Leckrone.
Grunsfeld, an astrophysicist who has spent more time working on the orbiting Hubble than anyone, did the honors.
"Hubble isn't just a satellite," he said. "It's about humanity's quest for knowledge."