In what amounted to electronic brain surgery, a space-suited astronaut cut through shielding on a broken camera deep inside the Hubble Space Telescope on Saturday, removed a cover plate that wasn't designed to be taken off in orbit, used a custom tool to pull out four blown circuit boards, and then installed a fresh set.
Running up to an hour ahead of schedule at one point, astronomer-astronaut John Grunsfeld, a self-described "Hubble hugger" making his third visit to the telescope, then spliced in an electrical cable and connected it to a new low-voltage power supply that replaced one destroyed in 2007 by a catastrophic short circuit.
The improbable repair of the Advanced Camera for Surveys went smoothly, with virtually no problems of any significance, and by 2:56 p.m., the final connections had been made, catching ground engineers by surprise.
"All connectors are mated," astronaut Michael Good radioed from Atlantis.
"Houston copies. Again, great work on that," astronaut Dan Burbank replied from mission control. "We've got to modify our aliveness test. It may take a little bit longer, didn't expect to be this far along."
"Well that's good news, thanks Houston."
Grunsfeld and crewmate Andrew Feustel then gathered their tools and equipment while engineers at the Goddard Space Flight Center in Greenbelt, Md., sent commands to verify the sophisticated instrument's three camera channels were properly connected.
Mission control commentator Pat Ryan reported at 3:22 p.m. that the Advanced Camera for Surveys had, in fact, passed its initial aliveness test. The crew was informed at 3:51 p.m.
"Atlantis, Houston, for EVA. We have a good aliveness test on ACS," Burbank radioed.
"Woo hoo!" someone exclaimed from orbit.
"Ah, that's unbelievable!" Grunsfeld said.
"Nice work, guys," Atlantis commander Scott Altman radioed. "Congratulations to you John, and Drew, for a great effort. I know it was made possible by all the folks who really put a plan together in record time to save ACS. So our thanks to them as well."
"Great words, Scooter," Grunsfeld agreed.
A more detailed functional test was planned for Saturday evening to determine the camera's overall health.
Going into the unprecedented repair, only one of the advanced camera's channels, the so-called solar blind camera, was still functioning. Assuming the new circuitry performs as expected, engineers hope to revive the camera's heavily used wide-field channel and, with luck, its powerful high-resolution channel.
Coupled with the successful installation of the $88 million Cosmic Origins Spectroscope earlier Saturday, Grunsfeld and Feustel chalked up a flawless spacewalk, accomplishing two of the crew's major objectives.
"I thought today's EVA was just absolutely amazing," said Hubble Program Manager Preston Burch. "We struggled a little bit here the first day or two and we didn't really quite know how it was going to play out today. Because you just never know. ... John Grunsfeld and Drew Feustel just made it look so easy out there. It was just absolutely amazing."
The six-hour 36-minute spacewalk ended at 4:11 p.m., within a few minutes of the targeted time, when Grunsfeld and Feustel began repressurizing Atlantis' airlock. Saturday's EVA, or extravehicular activity, the third of five planned by the Atlantis astronauts, pushed the crew's total to 21 hours and 52 minutes. Total Hubble EVA time in 21 spacewalks over four servicing missions stands at 151 hours and two minutes. Grunsfeld now ranks fourth on the list of most experienced spacewalkers, with 51 hours and 28 minutes of EVA time during seven Hubble spacewalks over three missions.
The day's work began with removal of the no-longer-needed COSTAR corrective optics package and installation of the Cosmic Origins Spectrograph, a swap that took about two-and-a-half hours to complete and came off without a hitch.
After COS was installed, Feustel, mounted on the end of the shuttle Atlantis' robot arm, carried the 800-pound COSTAR to the same storage box used to carry the new spectrograph into orbit.
"Just an unbelievable view," Grunsfeld radioed his crewmate. "I've got you and COSTAR, riding the arm, the Earth's limb in view, the curvature of the beautiful blue Earth and a half moon setting."
"Take a picture, John," someone said.
A few minutes later, ground controllers reported a successful COS aliveness test, indicating the new instruments was properly plugged into Hubble's power and data management system.
"Drew and John, excellent job getting COS inside and COSTAR out and safe to come home," astronaut Michael Massimino radioed from Atlantis' flight deck.
"I just want to add a special congratulations to ... all the folks at the University of Colorado-Boulder and Ball Aerospace for getting COS up here after all these many years," Grunsfeld said.
The ACS repair work began a few minutes past 1 p.m. Working inside the cramped confines of a Hubble instrument bay, Grunsfeld used a custom grid cutter tool to remove electromagnetic shielding from the phone booth-size camera and then removed six of the Torx fasteners securing a cover plate.
"Number one is out, Bueno," Grunsfeld radioed crewmate Michael "Bueno" Good. "Yay!" A moment later, he added: "I don't think brain surgeons go 'yoo hoo' when they pull something out."
After screwing in mounting posts, he attached a clear plastic "fastener-capture plate" designed to trap the small, non-captive screws holding the cover plate in position.
"This activity is dedicated to studying the behavior of tiny screws in space," Grunsfeld joked. "All the screws are out, Bueno."
Grunsfeld then used a power screwdriver to remove the 26 remaining Torx-head fasteners and pulled the cover plate, and the trapped free-floating screws, off to expose four critical circuit boards. Using a custom tool, he extracted the cards one at a time with no problem and replaced them with a box containing four new cards.
"Those cards look new," Grunsfeld said.
"Not like the ones we've been abusing for a couple of years (in training)," Feustel joked.
The final step in the repair job was to wire in a new low-voltage power supply designed to power the high-resolution and wide-field channels of the camera.
"So now we're 60 percent of the way through this servicing mission, we've accomplished five and a half of our top six priorities, the other half being the installation of the other battery module and that won't happen until (Monday)," Burch said.
"But at this point we're feeling really good. I think you can say at this point in time, Hubble has reached a new high in terms of its capability with what we have today. We've also made huge strides in terms of restoring the health of the observatory and the next couple of days, we expect to finish up the rest of the work we have planned."
During a news briefing Friday, Hubble Project Scientist Dave Leckrone made a Joe Namath-style bet on the outcome of today's spacewalk.
"I have a prediction," he said. "We've always said EVA 3 was going to be the most difficult and the most challenging, and I predict it's going to go more smoothly than any other EVA on this mission. I just think that's some version of Murphy's Law that's going to lead us in that direction."
He was right.