Atlantis astronauts packed equipment and trash from the International Space Station yesterday for the last ride home.
The Italian-built storage pod will be loaded into Atlantis' payload bay, in advance of the shuttle's departure from the station early on Tuesday.
The 13-day mission, the last of NASA's 30-year-old space shuttle program, is due to end with a landing at the Kennedy Space Center in Florida at 5.57am EDT on Thursday.
“This is really the last train out of town,” Atlantis commander Chris Ferguson said during an in-flight interview. “I don't think the full magnitude of everything is really going to hit us until after the wheels stop.”
Ferguson and his three crewmates delivered more than five tonnes of food, clothing, equipment and other supplies for the outpost, a $100 billion project of 16 countries that was finished earlier this year after more than a decade of construction 220 miles above Earth.
With help from the six-member live-aboard station crew, the astronauts also packed up 2.5 tonnes of old equipment, including 12 laptop computers, foam packaging and other items no longer needed on the station. In all, the crew put in the equivalent of 150 hours of labour transferring cargo, plus oversaw a spacewalk by two space station astronauts to pack up a refrigerator-sized coolant pump that broke last year.
The supplies aboard Atlantis are intended to tide over the station until NASA's newly hired cargo delivery firms begin flying next year. “The space station is actually in very good shape now for the retirement of the space shuttle,” said flight director Chris Edelen.
NASA meanwhile, wants to ramp up development of a new capsule-style spacecraft and heavy-lift booster that can ferry people into deep space, beyond the station's orbit where the shuttles cannot fly.
Crew ferry flights to the station will be handled exclusively by Russia until and unless US firms develop spaceships capable of orbital spaceflight.
NASA is supporting efforts by four firms - Boeing, Space Exploration Technologies, Sierra Nevada Corp and Blue Origin, a space travel start-up backed by Amazon founder Jeff Bezos - with technology development contracts worth $269 million.
NASA hopes the new vehicles will be ready to fly in about 2015. Russia charges the US more than $50 million per person for Soyuz capsule transportation and training.
Atlantis arrived at the station on July 10, becoming the 37th and final mission to the station. Over the past 30 years, NASA also flew 98 other shuttle missions to deploy satellites and observatories, including the Hubble Space Telescope, and to conduct research and test technologies.
The end of the program will hit central Florida, Houston and other shuttle operational hubs hard, with thousands of engineers and technicians due to lose their jobs shortly after Atlantis lands.
“You have to come to terms with the end before you can really put on a new beginning,” Ferguson said.
“I think once we can finally get over the fact that the shuttle is gone ... I believe we'll begin to pick up the pieces and everyone will see that we really do have some vibrant programs out there that we're working on.”