Atlantis, upper left, and the International Space Station circle the Earth on Saturday. Raffaello,
the Multi-Purpose Logistics Module that launched aboard the orbiter, is visible to the right of the
shuttle cargo bay. The station's robot arm extends just to the right of Raffaello.
Photo credit/NASA TV
The Atlantis astronauts re-activated a once failed General Purpose Computer on Saturday, temporarily returning the processor to action while experts in Mission Control assessed which responsibilities it will shoulder when the STS-135 crew undocks from the International Space Station and descends to Earth to mark the end of NASA's 30-year shuttle program.
"It looks like it has passed the test," Atlantis commander Chris Ferguson informed flight controllers after more than six hours of simultaneous GPC 4, 2 and 1 activity.
The spacecraft is equipped with five GPCs for redundant management of major functions, including guidance, navigation and control. One of the processors holds backup flight control software. Late Thursday, GPC 4 failed. It was successfully re-initiated but placed in a standby mode until Saturday's test.
Following the trial, GPC 4 rejoined GPC 3 in standby, while the mass memory was dumped. Late in the day, the flight control team scheduled another test of GPC 4 for Sunday, when the processor will be given a systems management role.
Provisionally, it was decided GPC 4 will be activated for the shuttle's undocking early Tuesday.
GPC 3 also failed to activate during the shuttle's July 10 rendezvous and docking with the space station because of a damaged switch. It, too, was successfully re-initiated.
Meanwhile, Ferguson, Atlantis pilot Doug Hurley and mission specialists Sandra Magnus and Rex Walheim paused Saturday in their cargo transfers to pay tribute to the many workers who've participated in the long running shuttle program.
Chris Ferguson, top center, displays a U. S. flag flown aboard
STS-1, NASA's first shuttle mission. The banner, delivered
by the Atlantis crew, will remain aboard the station until it is claimed
by the first astronauts launched aboard a U. S. commercial space
transport. Ferguson is surrounded by the crews of Atlantis and the
space station. Photo Credit/NASA photo
As part of the tribute, they placed a small American flag that orginally flew aboard STS-1, the first shuttle mission, in 1981 on the station, where it will remain until it is claimed by the astronauts of the first commercially launched U. S. crew transport to reach the orbital outpost.
Once back on Earth, the commemorative flag will be held until it accompanies the first crew of U. S. astronauts launched to a destination beyond low Earth orbit, said Ferguson.
The 13-day STS-135 mission, launched July 8, delivered enough food, spare parts and research gear to the station to sustain six person operations through 2012, permitting NASA to transition to commercially launched re-supply services.
On Saturday, the Atlantis crew crossed the 90 percent threshold in a cargo exchange with the station that will exceed nine tons.
The crew of the 26-year-old orbiter will re-stow the Raffaello Multi-Purpose Logistics Module, which carried up most of the cargo, on Monday. Raffaello was temporarily moved from the shuttle to the station on July 11.
Atlantis is scheduled to undock on Tuesday at 2:28 a.m., EDT.
The astronauts will prepare for a descend to Earth on Thursday, touching down at the Kennedy Space Center at 5:57 a.m., EDT.