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Astronauts in home stretch of marathon mission

The Endeavour astronauts are preparing for a fifth and final spacewalk Monday before departing the International Space Station Tuesday after an 'extremely successful' mission.

JOHNSON SPACE CENTER, Houston--Despite problems that forced spacewalk replanning, an impromptu toilet repair and work to fix the space station's carbon dioxide scrubber, the shuttle Endeavour's ongoing assembly mission is going well, the commander said Sunday, with most major objectives now accomplished. A fifth and final spacewalk is planned for Monday.

During four earlier spacewalks and near daily use of three robot arms on the shuttle and the space station, the astronauts have attached a large experiment platform to the Japanese Kibo lab module, installed research instruments and critical spare parts, replaced aging solar array batteries and deployed a jammed spare parts attachment mechanism.

The record 13-member crew of the shuttle-space station complex waves to reporters after an orbital news conference. NASA TV

"We even managed to have dinner a couple of nights with our wonderful hosts here," Endeavour skipper Mark Polansky told reporters during an in-flight news conference. "So all in all, I think it's an extremely successful mission in spite of a lot of really interesting curve balls that have been thrown our way."

One final spacewalk by astronauts Christopher Cassidy and Thomas Marshburn is planned for Monday to rewire a gyroscope control circuit, to repair insulation on a Canadian construction robot, to install two Japanese television cameras and to deploy another spare parts stowage mechanism.

While he doesn't anticipate any major problems, "I think we're all keenly aware that EVAs carry some risk to them and so we're going to be very, very deliberate and careful about the last EVA," or extravehicular activity, Polansky said. "Because in my book, the last one you do is always the one you have to watch out for the most."

The six members of the lab's Expedition 20 crew, along with Polansky and his six shuttle crewmates, gathered in the station's Harmony module for the news conference, floating shoulder to shoulder in the normally roomy confines.

Shuttle spacewalker David Wolf, veteran of a long-duration stay aboard the old Russian Mir space station, said life aboard the International Space Station symbolizes the worldwide effort that's gone into building history's largest spacecraft.

The space shuttle Endeavour, docked to the International Space Station, with the Japanese Kibo module extending to the right and the U.S. Destiny lab to the left. NASA TV

"It's really fascinating to be here," he said. "I'm looking down a corridor, maybe 60, 80 feet, through several modules into a Russian segment. To my left is a European segment, to my right is a Japanese segment, a U.S. space shuttle behind me. And as you go through here, you hear different languages, you hear different music, it's like going around the world within the spacecraft as it goes around.

"The equipment is made out of different materials, there's kind of different odors and feelings as you go around," he said. "We've put together a vehicle that is truly international and brought together a truly international crew representing the whole world. We're undertaking, perhaps, one of the most spectacular engineering achievements that humans have ever conducted. And so it's just fabulous in many dimensions."

Japanese astronaut Koichi Wakata, wrapping up a four-month stay aboard the station, told reporters he's looking forward to a hot bath, fresh sushi and cold noodles after he returns to Earth aboard Endeavour. In case anyone's wondering, he said his high-tech "J-ware" underwear, designed to stay clean and odor-free after extended use, is working well.

"In two months, I was wearing these underwear and there was no smell and nobody complained about my underwear," he said, speaking through an interpreter. "So I think that new J-ware underwear is very good for myself and my colleagues."

Engineers at the Johnson Space Center in Houston, meanwhile, are manually controlling a NASA carbon dioxide removal system aboard the station that shut down Saturday after a heater controller problem that apparently tripped a circuit breaker.

With six full-time station astronauts and seven shuttle crew members on board the shuttle-station complex, carbon dioxide removal is a critical requirement. But the U.S. system is working at near normal capacity in manual mode.

"Bottom line, we're operating it manually with commands from the ground and we're scrubbing CO2 at a level we're happy with," said Flight Director Derek Hassmann. "After the shuttle leaves, we're going to talk about actually removing and replacing that heater controller."

If all goes well, Endeavour will undock Tuesday and land back at the Kennedy Space Center on Friday.