NASA's orbiting astronauts detached a huge storage bin full of trash from the International Space Station on Monday and loaded it aboard Atlantis for the last shuttle ride back to Earth.
The astronauts used a hefty robotic arm to move the bus-size canister, stuffed with nearly three tonnes of packing foam and other space station refuse.
It was the last job shared by the shuttle and station crews, numbering 10 astronauts altogether. The hatches between the two spacecraft were to be sealed less than two hours later in what was expected to be an emotional goodbye.
"Be sure to give them lots of hugs from all of us!" Mission Control said in a written message to the four shuttle astronauts.
Atlantis will undock from the space station early Tuesday and aim for a pre-dawn touchdown Thursday. Then it will be retired.
It will be some time before there are so many people aboard the space station again. The Russian Soyuz capsules — the only way to get astronauts to the space station for at least the next few years — carry no more than three.
Most of the new commercial spacecraft under development also would seat three, although a few may hold four or more. These are still three to five years away from flying.
The 6.4-metre-long storage canister — named Raffaello, given its Italian roots — was launched aboard Atlantis back on July 8. It carried up nearly five tonnes of food, clothes and other household goods — enough to keep the space station going for another year.
NASA wanted to stockpile the orbiting lab in case private companies get delayed in launching their own cargo ships. The first such supply run is expected by year's end.
The retirement of NASA's three remaining shuttles has been in the works since 2004, barely a year after the Columbia disaster. Then, President George W. Bush announced a new exploration vision aimed at returning astronauts to the moon. President Barack Obama nixed the moon in favour of an asteroid and Mars. The target launch dates: 2025 for an asteroid and the mid-2030s for the red planet.
Atlantis will remain at Kennedy Space Center for retirement, going on public display. Discovery and Endeavour will be transported to museums in suburban Washington and Los Angeles, respectively.