Astronauts Make Repairs, Move Cargo on Final Shuttle Flight
In an occurrence which became somewhat of a tradition for shuttle crews and those of the International Space Station expeditions, the Expedition 28 crew and the STS-135 Atlantis astronauts formed a microgravity circle for a portrait aboard the orbiting complex's Kibo laboratory of the Japan Aerospace Exploration Agency. This image was taken on July 15, 2011 during NASA's final shuttle mission STS-135 aboard Atlantis.
Credit: NASA

This story was updated at 9:16 a.m. EDT.

HOUSTON – The space shuttle Atlantis' astronauts are spending another day doing heavy lifting and maintenance today (July 16).

The crew repaired a broken latch on a compartment inside Atlantis that contains canisters used to scrub carbon dioxide from the orbiter's cabin atmosphere. These canisters are not used while Atlantis is docked to the International Space Station, but will be needed once the shuttle departs from the orbiting outpost.

Commander Chris Ferguson, pilot Doug Hurley, and mission specialists Sandra Magnus and Rex Walheim also continued their work to transfer and store hardware and other supplies that were brought up to the space station in Atlantis' mid-deck and inside the Raffaello module. [Photos: NASA's Last Shuttle Mission in Pictures]

To start their day, the spaceflyers were treated to a special wakeup message from hit R&B artist Beyonce Knowles, as mission controllers on the ground continue to evaluate the cause of a computer glitch that occurred earlier this week.

This panoramic view from the International Space Station, looking past the docked shuttle Atlantis' cargo bay and part of the station including a solar array panel toward Earth, was taken on July 14, 2011 as the spacecraft passed over the Southern Hemisphere. Aurora Australis or the Southern Lights can be seen on Earth's horizon and a number of stars are visible also.
This panoramic view from the International Space Station, looking past the docked shuttle Atlantis' cargo bay and part of the station including a solar array panel toward Earth, was taken on July 14, 2011 as the spacecraft passed over the Southern Hemisphere. Aurora Australis or the Southern Lights can be seen on Earth's horizon and a number of stars are visible also.
Credit: NASA

Shout out from Beyonce

Atlantis' four astronauts, who are on an overnight schedule, woke up at 11:29 p.m. EDT (0329 GMT) to the song "Run the World (Girls)" by Beyonce Knowles. The singer also recorded a special message for the crew.

"Good morning, Atlantis. This is Beyonce," the Houston native said. "Sandy, Chris, Doug and Rex, you inspire all of us to dare to live our dreams, to know that we're smart enough and strong enough to achieve them. This song is especially for my girl, Sandy, and all the women who've taken us to space with them and the girls who are our future explorers." [Astronaut Rock: NASA's Final Shuttle Wakeup Songs]

"Good morning, Houston," STS-135 mission specialist Sandy Magnus replied. "A big thanks to Beyonce for taking the time out of her schedule to record us a greeting, and we're ready for another day here on Atlantis and hopefully we as a team at NASA can keep our inspirational work up for the young people of America."  

Yesterday, the Atlantis' astronauts were able to get one of the orbiter's computers working again after it failed Thursday evening and set off an alarm that interrupted their sleep period. Ground teams are still trying to determine the root cause of the problem.

The crew spent around 45 minutes Thursday (July 14) transferring the troublesome computer's program onto another, and this morning commander Chris Ferguson and pilot Doug Hurley worked with ground teams in Mission Control to reboot the workstation. The astronauts were able to get the computer back online, and ground controllers are now poring through the data to try to identify what may have caused the glitch.

"Right now, there's no smoking gun that they've identified as the cause of the failure," lead shuttle flight director Kwatsi Alibaruho told reporters in a briefing Friday (July 15). "Until we complete our analysis of the [data], we have no idea what caused the failure."

Engineers will spent the bulk of yesterday assessing whether the computer suffered a software malfunction, or if it experienced what is called a "transient hardware failure," 'which can be caused by a number of things, including temporary exposure to higher than normal radiation levels.

Computer problems in space

A seemingly unrelated issue cropped up with a separate onboard computer earlier in the mission, as Atlantis prepared to link up with the International Space Station, but mission controllers later determined that this was due to a sticky switch rather than a problem with the computer itself.

In both cases, the astronauts were able to successfully reboot the systems and restore the computers to full functionality, which could be a good sign, particularly with regards to yesterday's failure.

"The fact that [the computer] was able to be reinitialized is very telling," Alibaruho said. "We've demonstrated the ability to bring both of those computers up to full computational awareness, and that's a meaningful capability that we have."

The space shuttle carries five onboard computers that work together to create a highly redundant system. One of these computers is always designated a backup, and the four others combine to make up the orbiter's primary computer system that manages guidance, navigation and control, Alibaruho explained.

Typically, during non-critical times on orbit, such as while the shuttle is docked to the space station, the orbiter will operate using two of the four primary workstations. But, during crucial moments in flight, such as docking operations, re-entry into the Earth's atmosphere and landing, all five computers are powered up.

Cautiously optimistic

Since in both cases the computers came back online after being rebooted, NASA can technically consider all five as fully functional. Still, this determination will have to wait until analysis of the failure is complete and engineers can pinpoint its root cause. [Stunning Photos of Last Shuttle Launch From Above]

"I do have a saying that you're not paranoid if they really are after you," Alibaruho joked. "I'm cautiously optimistic that we'll have a healthy data processing system. But, we will be watching closely."

And while the type of computer failure seen yesterday is unusual, Atlantis has been performing extremely well on orbit, he added. Yet, Alibaruho said he will not rest easy until they have identified the reason for the failure.

"I consider every issue a major issue until I believe we fully understand it and have no reason to think otherwise," Alibaruho said. "We haven't seen any obvious software problems, and honestly, that's the thing I tend to worry about the most. Once we complete the analysis of the dumped data and don't see any indications of that scenario, then I will be a bit more comfortable. But, I never let myself get too comfortable until we have all of our friends with their boots on the ground."

Atlantis launched toward the International Space Station on July 8. The astronauts are more than halfway through their 13-day mission and are expected to return to Earth and land at NASA's Kennedy Space Center in Florida on July 21.

You can follow SPACE.com Staff Writer Denise Chow on Twitter @denisechow. Visit SPACE.com for complete coverage of Atlantis' final mission STS-135 or follow us @Spacedotcom and on Facebook.