Space Shuttle Computer Failure Wakes Sleeping Astronauts

Space shuttle Atlantis is seen docked at the International Space Station on July 14, 2011 during the STS-135 mission, the final flight of NASA's 30-year shuttle program. CREDIT: NASA TV View full size image

HOUSTON – The shuttle Atlantis' astronauts were roused from their sleep tonight (July 14) to deal with a glitch that affected one of their orbiter's onboard computers.

The shuttle astronauts were awakened by an alert tone at 6:07 a.m. EDT (2207 GMT), signaling a failure with one of Atlantis' General Purpose Computers (GPCs). The glitchy computer runs Atlantis' systems management, and mission controllers walked shuttle commander Chris Ferguson through the process of switching its programs onto one of the shuttle's backup systems.

After activating the backup computer, Ferguson and his crew went back to bed, with Mission Control assuring the astronauts they'll get some extra sleep time to make up for the late-night malfunction.

The space shuttle carries five onboard computers for redundancy, with one always designated as a backup. The four other computers work together to make up the orbiter's primary computer systems, NASA officials said. [Photos: NASA's Last Shuttle Mission in Pictures]

During non-critical times on orbit, the shuttle typically operates using two of the four available primary workstations.

"One of those two is always used to run guidance, navigation and control functions and the other is used to run systems management," NASA officials said.

The computer that failed runs Atlantis' systems management, and the astronauts worked to transfer its functions to one of the other available monitors. After testing and analysis by ground teams in Mission Control, it was confirmed that the critical program was successfully moved over to a separate computer.

"You all have done an absolutely fabulous job," mission controllers radioed to the shuttle crew. "We have polled the room; everyone is ready for you to go back to sleep."

Since the crew was kept up later than expected, they will be given an extra 30 minutes to sleep tomorrow  morning (July 15), with their wakeup call now scheduled to come at around 1:00 a.m. EDT (0500 GMT) Friday. [Astronaut Rock: NASA's Final Shuttle Wakeup Songs]

The astronauts also experienced an unrelated computer issue Sunday (July 10) during their rendezvous and docking with the International Space Station. At that time, the crew encountered a small hiccup with one of the computers (not the same one that failed tonight), but mission controllers suspected that the problem was more of a switch issue than a glitch with the computer itself.

The next day, the astronauts rebooted the system, and ground teams reported that the computer was brought back up to full functionality with no further concerns.

Atlantis is roughly halfway through its STS-135 mission, the last ever for NASA's storied space shuttle program. Atlantis launched July 8 and is slated to touch down July 21. The shuttle is delivering a huge load of spare parts and supplies to the International Space Station.

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.