President Barack Obama told the crew of the space shuttle program's last mission that he's proud of them and the "amazing feats" they are accomplishing in space.
Friday's phone call represented the final Earth-to-space communication between the White House and a shuttle crew. Ten astronauts in all gathered to take the call, including the four crew members of the shuttle Atlantis and the six residents of the International Space Station.
Obama couldn't resist slipping in a joke or two. When the astronauts came on the line, the president feigned surprise, saying, "I was just dialing out for pizza and I didn't expect to end up in space."
Later in the call, he referred to the fact that 10 people had to share the space station's two toilets and Atlantis' sole bathroom. "My wife and my daughters are always crowding me out — hopefully you guys have a more organized arrangement than we do."
But the main themes of his conversation were praise and thanks for the shuttle program's service.
"I know that there have been thousands who have poured their hearts and souls into America's space shuttle program over the last three decades that are following this journey with special interest," he said. "And to them and all the men and women of NASA, I want to say thank you. You helped our country lead the space age, and you continue to inspire us."
Atlantis is in the midst of a 13-day resupply mission to the space station. Its landing, currently set for next Thursday, will spell the end of the 30-year space shuttle program. Atlantis and its two sister shuttles, Discovery and Endeavour, are to be retired to museums.
The president asked about the robotic satellite-refueling experiment that was brought to the station on Atlantis, and said it was a "good reminder of how NASA technology and reearch oftentimes has huge spillover effects into the commercial sector."
Looking ahead to future
Obama said NASA would continue to push the frontiers of space exploration and human spaceflight in the post-shuttle era. The White House has set a goal of sending astronauts to a near-Earth asteroid by 2025 and to Mars and its moons by the mid-2030s.
In the meantime, commercial space taxis will be developed to take supplies to the space station and eventually take astronauts up as well. Atlantis' crew is leaving behind a U.S. flag that was flown on the very first shuttle mission, to be turned over to the next crew to arrive on the station on a spaceship launched from U.S. soil.
"I understand it's going to be sort of like a 'capture the flag' moment here for commercial spaceflight," Obama said. "So good luck to whoever grabs that flag."
Atlantis' commander, Chris Ferguson, said "we sure hope to see some of our commercial partners climbing on board really soon." NASA's timetable calls for such flights to begin around 2015. Between now and then, the space agency will have to purchase rides on Russian Soyuz craft at a price of up to $63 million a seat.
Earlier in the day, Atlantis' crew fixed another one of their main computers, after it failed and set off an alarm that shattered their sleep. The first computer failure occurred just before Atlantis docked with the space station on Sunday. New software loads took care of both problems, and NASA declared all five of Atlantis' main computers — three primary systems and two backups — to be working.
The five computers are critical for a space shuttle's return to Earth — so crucial that multiple shutdowns, in certain circumstances, could prompt an early return home.
Computer failures like this are extremely rare in orbit, lead flight director Kwatsi Alibaruho said. The two problems appear to be quite different, he noted. The first was caused by a bad switch throw; the second possibly by cosmic radiation.
"The fact that we did have two computer failures on a same flight on a spacecraft that's otherwise performing beautifully, that's not at all lost on me," Alibaruho told reporters.
"I do have a saying that you're not paranoid if they really are after you, so I am cautiously optimistic that we'll have a healthy data-processing system" for Atlantis' undocking and return to Earth next week, he added. "But we will be watching closely."
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.
Too busy to reflect
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 shuttle delivered several tons of food, clothes and other household goods for the station; it will return loaded with old station equipment and trash.
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 spacefliers, "Hey, you know, this is the last joint meal that we're ever going to have aboard a space shuttle."
Ferguson said it was a "sobering, somber moment."
"But at the same time, we're extremely fortunate to have had 37 missions, I thnk, to the International Space Station now, so we're very lucky to have done this," he said.
Hurley said his most memorable moment of the 13-day mission, so far, was seeing 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: an "incredible" display of 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.
This report includes information from msnbc.com and The Associated Press.