(AP) -- The pilots on NASA's last space shuttle flight fixed another one of their main computers Friday after it failed and set off an alarm that awoke the entire crew.
Atlantis' commander, Christopher Ferguson, said the alarm sounded an hour or so after the four astronauts had gone to bed, during the deepest part of their sleep.
"We all woke up and looked at one another, and we were wondering really what was going on," he said in an interview with The Associated Press on Friday morning. The astronauts rushed to the flight deck and switched to a backup computer. Within a half-hour they were back in bed.
It was the second such failure of their space station delivery mission. Just before docking to the International Space Station on Sunday, another of the five main shuttle computers conked out. New software loads took care of both problems, although engineers were still trying to figure out why the trouble occurred in the first place.
The five computers are critical for a space shuttle's return to Earth. Atlantis will make the last journey home of the 30-year space shuttle era next Thursday.
"We're doing well here," Ferguson told the AP, "and I'm confident everything's going to look good when we undock in a couple days."
Ferguson and his co-pilot, Douglas Hurley, said they're still too busy moving items back and forth between the linked Atlantis and space station to dwell on the looming end of the shuttle program.
The topic came up at Thursday's special all-American dinner of grilled chicken, barbecued beef, baked beans, corn and Hostess apple pie. Ferguson said he told the nine other space fliers, "Hey, you know, this is the last joint meal that we're ever going to have aboard a space shuttle."
"It's a little bit of a sobering, somber moment," Ferguson said. "But at the same time, we're extremely fortunate to have had 37 missions, I think, to the International Space Station now, so we're very lucky to have done this."
Ferguson said his most memorable moment of the 13-day mission, so far, occurred just before last weekend's docking by Atlantis. He was at the shuttle controls and Atlantis was hovering just several hundred feet away from "this incredibly mammoth space station."
"It's just a feeling of awe, and you're humbled by what humans can create when they work together to do things in space," he said. "It's an incredibly memorable moment and I will never, ever, ever duplicate it or forget it."
Seared into Hurley's mind are the faces of the two astronauts who were outside, just a few feet away, as he operated the robot arm during Tuesday's spacewalk, the last one of the shuttle program.
"It really seemed like it was out of a science fiction movie," he said. "You could see the expression on their faces."
Another highlight for Hurley he said he'll keep with him: seeing an "incredible" aurora australis, or southern lights, on Thursday night.
As their time at the space station wound down, the shuttle crew got another celebrity call Friday, this time from musician Paul McCartney.
"Good luck on this, your last mission. Well done," McCartney said in a prerecorded message. The wake-up music was "Good Day Sunshine" by the Beatles. The previous two days, Elton John and R.E.M.'s Michael Stipe sent greetings.
Early Friday afternoon, a live VIP call was scheduled - from the Oval Office.
President Barack Obama planned to call the four shuttle fliers and six station residents. His plan for U.S. space exploration after the shuttles is to put orbital launches in the hands of private companies, and get NASA working on human expeditions to an asteroid and Mars.
Explore further: Last 4 shuttle astronauts arrive for countdown