Their two-week-plus mission finally winding down, space shuttle Endeavour 's astronauts released a mini research satellite Thursday and said it's time to come home.
Endeavour and its seven astronauts are aiming for a touchdown late Friday morning at NASA's spaceport.
"I'm ready to get back ... I think I have a landing in me, so don't want to get anybody on the ground worried about that," commander Mark Polansky said in an interview with The Associated Press.
In one of NASA's longer shuttle flights, Polansky and his crew put a new addition onto the international space station — a porch for Japan's massive $1 billion lab — and freshened up the place with batteries, experiments and spare parts. They rocketed into space July 15.
Thursday marked Day 15 in space for Polansky and all but one of his crew. For Japanese astronaut Koichi Wakata, Thursday marked Day 137. He flew to the space station back in March, becoming the first person from Japan to live at the orbiting outpost.
Wakata said he's longing for sushi.
"That's the first thing that I'd like to have and also a hot spring in Japan sometime in the near future," Wakata told the AP.
One of Wakata's space station experiments involved wearing a new type of anti-bacterial, water-absorbent, odor-eliminating underwear provided by Japanese researchers.
He's bringing back the used undergarments for scientific analysis.
"I haven't talked about this underwear to my crew members," Wakata said, drawing a big laugh from his shuttle colleagues. "But I wore them for about a month, and my station crew members never complained for about a month, so I think the experiment went fine."
The underwear is called J-Wear, and includes a line of shirts, pants and socks as well. Wakata tested all of them during his mission. "We'll see the results after landing," Wakata said.
J-Wear is billed as being antistatic and flame retardant, which is especially important for spaceship wear. The clothes are also seamless, making them lighter and more comfortable, according to the Japanese Space Agency. The goal is "comfortable everyday clothes for life in a spaceship."
On Thursday morning, the shuttle astronauts released a small canister containing a navigation, rendezvous and docking experiment prepared by University of Texas and Texas A&M researchers. In the afternoon, they planned to launch an atmospheric density experiment, so scientists can better understand how orbiting objects move and eventually come down.
Over at the space station, meanwhile, the major air-purifying system on the U.S. side failed again, and the crew spent the day trying to fix the balky equipment. A carbon dioxide-removal system on the Russian side is still operating properly, and the six astronauts have backup methods for cleansing the cabin atmosphere.
But the American system is crucial for long-term space station operations and needs to be repaired as soon as possible. It overheated over the weekend and shut down, but flight controllers managed to work around the problem, at least for a few days.