This story was updated at 10:00 p.m. EDT.
HOUSTON — Two spacewalking astronauts opened up a camera inside the Hubble Space Telescope Saturday to make unprecedented repairs Saturday after successfully adding a brand new instrument to boost the observatory's view on the universe.
Astronauts John Grunsfeld and Andrew Feustel ventured outside the shuttle Atlantis for more than six hours to give the 19-year-old Hubble a powerful new spectrograph and revive the observatory's broken main camera.
It was the third of five consecutive spacewalks for the Atlantis astronauts to overhaul Hubble for the fifth and final time to extend its lifetime through at least 2014. NASA expected Saturday's work to be the crew's toughest job yet. After all, the broken imager — Hubble's Advanced Camera for Surveys — was never designed to be fixed in space.
But the physical repair job went off without a hitch and was free of the glitches that plagued the two earlier spacewalks.
"It was smooth sailing for the team today," Atlantis commander Scott Altman radioed Mission Control.
"Lots of people happy down here, as well," Mission Control called back.
After an initial power check of the camera, engineers at Hubble's mission operations center at NASA's Goddard Space Flight Center in Greenbelt, Md., performed a more in-depth test of its three science-collecting modes - which include a solar blind, wide-field and high-resolution imaging channel - to check their health.
"You never want to take these things for granted," Hubble program manager Preston Burch told reporters after the initial spacewalk repair, adding that it promised a more capable Hubble telescope. "We're enjoying the moment and savoring it."
Late Saturday, they completed a check of the camera's wide-field mode - a channel that was physically repaire in the spacewalk - but encountered a power glitch while checking its high-resolution imaging channel. Engineers hoped to revive the high-resolution mode indirectly by rerouting power through the repaired wide-field channel since there was not time to physically fix it during Hubble's service call.
Most of the survey camera's observations are made with the wide-field channel, so the impact to science, should the high-resolution mode stay offline, would be minimal, NASA officials said. Engineers continue to study the glitch, they added.
Hubble's Advanced Camera for Surveys was once the telescope's most-used instrument, but it suffered a power system failure in 2007 that left it nearly incapable of science. Engineers were only able to revive the ultraviolet-scanning solar blind channel.
Using custom-made tools, Grunsfeld removed two access covers and 32 screws from the camera's wide-field channel in order to reach four delicate computer cards inside. It was delicate work that the astronaut tackled bulky spacesuit glove-clad hands.
"Yay!" cheered Grunsfeld, an astrophysicist-turned-astronaut, as the first screw came out. "Somehow, I don't think brain surgeons go "yahoo" when they pull something out."
Working swiftly through the challenging repair, Grunsfeld plucked out the camera's four ailing computer cards and replaced them with an electronics box containing new ones. He and Feustel then hot-wired the box into Hubble's electrical grid by patching it into an external power box.
Engineers successfully powered up the camera in a so-called "aliveness test." Hubble scientists had high hopes for the repair but said repeatedly that it offered no guarantees and more tests were planned overnight. It was those tests that encountered the high-resolution channel power glitch.
"We have demonstrated the very first internal repair of an instrument in space today," said a jubilant Dave Leckrone, Hubble's senior project scientist, after the spacewalk. "This is an instrument that was dead, and it's now been demonstrated that it's alive."
Hubble's new cosmic eye
Before the repair, the astronauts also accomplished their initial spacewalk goal - installing the $88 million Cosmic Origins Spectrograph (COS) in Hubble. The phone booth-sized instrument will take light from distant quasars and scan its individual wavelengths to study the structure of the universe and chemical makeup of galaxies, stars and planets.
"COS was designed to be a go-for-broke, go as far as possible as fast as possible instrument," Leckrone said.
They plugged the new spectrograph into a slot that was occupied by a device known as COSTAR, which contained Hubble's vital corrective optics that were once used to clear its blurry vision.
When Hubble launched in 1990, it had a flawed mirror that left it near-sighted. Astronauts installed COSTAR, essentially glasses for Hubble, three years later to fix it, but the device is no longer needed since newer instruments already compensate for the flawed mirror.
"This is really pretty historic, holding the COSTAR," Grunsfeld said as they packed it away for the return to Earth.
The spacewalk began at 9:35 a.m. EDT (1335 GMT) and marked the seventh for Grunsfeld, who is making his third trip to Hubble. It was the second for Feustel and the 21st ever for Hubble as it orbits 350 miles (563 km) above Earth.
In addition to Saturday's work, Atlantis astronauts have a new wide-field camera, gyroscopes and batteries to Hubble, and fixed a vital computer data unit that beams images to Earth. Another tough repair awaits a different spacewalking team on Sunday.
The shuttle's 11-day mission is NASA's final service call to Hubble before the agency retires its three-orbiter fleet next year.
SPACE.com is providing continuous coverage of NASA's last mission to the Hubble Space Telescope with senior editor Tariq Malik in Houston and reporter Clara Moskowitz in New York. Click here for mission updates, live spacewalk coverage and SPACE.com's live NASA TV video feed.