HOUSTON (AP) -- Little work remained for shuttle Discovery's astronauts to do aboard the international space station Tuesday before they closed the hatches between the two spacecraft in preparation for their return trip to Earth.
The astronauts were to spend their last full day at the space station installing a backup drive system for the new Japanese lab's robotic arm and finish packing the spacecraft with equipment and science and medical samples to take back with them.
Astronauts aboard the shuttle-station complex were also scheduled to get some off-duty time Tuesday.
"We usually try and give the crews time off in the joint mission just to give them a little chance to relax because they work extremely hard," flight director Annette Hasbrook said.
Later in the day, the crews of Discovery and the space station planned to say their formal farewells during a brief ceremony before closing the hatches between the shuttle and the outpost in preparation for Wednesday's departure. The shuttle is set to land Saturday.
Discovery delivered the new lab named Kibo, Japanese for hope, to the space station last week.
The 37-foot lab, about the size of a bus, is the biggest room at the space station. Kibo also has a storage closet and a 33-foot robotic arm, which was successfully tested Monday.
The lab's third and final section - a "porch" for exterior experiments - and a second, smaller robotic arm will be delivered next year.
The shuttle also dropped off the space station's newest resident, Gregory Chamitoff. He traded places with Garrett Reisman, who is leaving after a three-month stay. Chamitoff's mission will last twice that long.
Reisman said that while he can't wait to see his wife again upon his return, he is going to miss one thing about his time on the space station.
"It's definitely floating," he said. "We call it floating but really it's more like flying because as soon as you push off you're moving through the air like some kind of superhero. To be able to do that every day as you're commuting to work is unreal."
Chamitoff said it's going to be hard for him initially when the hatches between the shuttle and the station close.
"After that, I'm with really good friends that I've spent years training with," he said, referring to the two Russian cosmonauts who have been living on the station for two months. "They will show me the ropes."