Space shuttle Atlantis was cleared to depart the international space station after a test Monday showed Russian computers that crashed last week can control the outpost's orientation.
Officials examined test data and decided the crucial computers controlled the station's thrusters properly. Atlantis is scheduled to undock Tuesday with a planned return to Cape Canaveral, Fla. on Thursday.
"Everything looked pretty good," said NASA spokesman Kyle Herring. "There was nothing that would give them any level of concern."
During the test, the space shuttle's thrusters took control of the joined craft so it could change positions to dump waste and water. Afterward, thrusters on the Russian side of the space station took over. During the third part of the test, U.S. computers sent commands to the Russian thrusters before the station's gyroscopes took over control.
"That's a big step in our checkout of the computers to make sure everything is working correctly," flight director Holly Ridings said Monday. "It's one of those things we want to see before we undock."
The revived computers had not commanded the Russian thrusters since last Tuesday, when six computer processors in the two systems started crashing. During the computer meltdown, Atlantis' thrusters helped maintain the station's orientation.
The computers were brought back to life over the weekend, but NASA and Russian managers wanted to make sure Atlantis wasn't needed for another day to give engineers on the ground more time to figure out the problem. Some lights, cameras and computers had been turned off on the space shuttle to preserve power in case the extra day was required.
The computers also control life support systems such as an oxygen generator, temperature and a carbon dioxide scrubber. Except for the oxygen generator, all the space station systems were turned back on over the weekend. Oxygen for the crews has come from other sources, such as a cargo ship on the Russian side of the station.
Atlantis' crew on Monday finished packing the shuttle for the return trip to Earth. They were given some free time Monday morning to enjoy the view on their last full day in the space station.
The shuttle's seven astronauts and the station's three crew members were set to say their goodbyes before hatches between Atlantis and the outpost are closed in preparation for Tuesday's departure.
Atlantis has been at the space station since June 10, adding to the size of the orbiting outpost 220 miles above Earth. The 11-day mission was extended to 13 days so that astronauts could repair a peeled-back thermal blanket near Atlantis' tail.
Twelve more construction missions are needed to finish building the space station before a 2010 deadline, when the shuttles are to be grounded permanently.
During four spacewalks, Atlantis' astronauts helped install a new truss segment, unfurled a new pair of power-generating solar arrays, repaired the thermal blanket and activated a rotating joint which will allow the new solar arrays to track the sun.
"It has been a challenging mission but a successful one," pilot Lee Archambault radioed Mission Control on Monday.
On Monday, flight controllers successfully tested the rotating joint and it began rotating automatically, allowing the solar arrays to track and sun and provide power to the station.
U.S. astronaut Sunita Williams spent her last full day in the space station showing the ropes to her replacement, U.S. astronaut Clay Anderson. She thanked flight controllers on the ground for their work during her more than six months in space, a record for the longest single spaceflight by a woman.
"I'm sad to say goodbye but that means progress is being made and it's time for the international space station to grow a little more," said Williams, her voice cracking with emotion. "The (space station) will always be a part of me."
She then played a recording of the Bee Gees' song, "Staying Alive," in Anderson's honor.
Meanwhile, a leader for almost 570 striking aerospace workers at the Kennedy Space Center in Cape Canaveral, Fla., warned Monday that the lack of training by replacement workers filling their jobs temporarily posed a safety risk in preparing for the next shuttle launch in August. Members of the machinists union began the strike last week, said Lew Jamieson.
United Space Alliance spokeswoman Tracy Yates said all the replacement workers are certified for their jobs and have previous experience in the tasks they are performing.
Associated Press writer Juan Lozano in Houston contributed to this report.