The shuttle Endeavour astronauts packed equipment and tested landing systems on Saturday before a scheduled Sunday homecoming at Florida's Kennedy Space Center, Reuters reported.
During their 16-day mission, the shuttle astronauts prepared the International Space Station for an expanded, six-member crew by delivering a water recycling system, a second toilet, two small bedrooms, a galley and additional exercise gear.
The astronauts also conducted four spacewalks to fix a long-standing problem that was hampering the station's solar-powered electrical system.
"We came up here with a very long list of objectives and (although) we encountered a glitch or two along the way, we managed to achieve them all," Endeavour commander Chris Ferguson said during an in-flight interview on Saturday.
"My mind is on the landing," he said, "but I'm extremely satisfied with what this fine crew has accomplished."
Endeavour is set to touch down at NASA's Florida base at 1:19 p.m. EST (1819 GMT) to wrap up the agency's fourth and final mission of the year.
But weather forecasts show possible crosswinds and thunderstorms near the landing site on Sunday. The shuttle could stay in orbit until the weather clears or land at Edwards Air Force Base in California instead, said Bryan Lunney, a NASA flight director.