Space Station Astronaut to Return to Earth Early
NASA astronaut Sunita Williams (center) and her Expedition 14 and 15 crewmates enjoy a light moment during a crew change ceremony aboard the International Space Station in April 2007. Clockwise from lower left are: Expedition 14 flight engineer Mikhail Tyurin, Expedition 14 commander Michael Lopez-Alegria, Expedition 15's commander Fyodor Yurchikhin and flight engineer Oleg Kotov.
Credit: NASA.

American astronaut Sunita Williams will return home from her mission to the International Space Station (ISS) a bit early this summer due to delays associated with NASA's next shuttle flight, the space agency announced Thursday.

Williams, an ISS Expedition 15 flight engineer, is now set to return to Earth in June aboard the space shuttle Atlantis following an 11-day assembly mission by the orbiter's STS-117 astronaut crew. Her replacement, NASA astronaut Clayton Anderson, will join the STS-117 crew roster as a late addition, NASA officials said.

"Since an earlier crew rotation was possible, NASA managers decided it would be prudent to return Williams and deliver Anderson sooner rather than later," the space agency said Thursday.

Williams, 41, first arrived at the ISS in December 2006 during its then-Expedition 14 mission and stayed on this month for the beginning of Expedition 15. She and Anderson were initially expected to swap places during NASA's STS-118 shuttle flight aboard the shuttle Endeavour in late June.

But that mission was rescheduled to no earlier than Aug. 9 following a string of delays caused by hail-spawned fuel tank damage that prevented an initial March 15 launch of Atlantis' STS-117 mission. Atlantis is now set to launch towards the ISS no earlier than June 8.

A U.S. Navy commander making her first spaceflight, Williams has repeatedly said that she was prepared to return home early or late depending on what ISS mission managers saw as the best move for the station. Earlier today, she told reporters that she and her family had weathered similar experiences during her long deployments abroad with the Navy.

"It comes with the job, you just need to be flexible," Williams told USA Today Thursday in a space-to-ground video link. "It's an operational ship, and an operational station and we just need to take care of it the right way and do the right things for the program."

While Williams is returning to Earth on an earlier shuttle flight, she will be spending about the same amount of time in space - just over six months - as originally planned, NASA spokesperson Kylie Clem told SPACE.com Thursday.

Mission tweaking

Returning Williams to Earth in June does add some additional complexity to an already tricky space station construction flight.

Commanded by veteran NASA shuttle flyer Rick Sturckow, Atlantis' now seven-astronaut STS-117 crew will deliver a 17.5-ton pair of new starboard trusses and solar arrays to the ISS. The mission was delayed to June 8 after a freak storm over Atlantis' launch pad gouged thousands of dings into the orbiter's foam-covered external fuel tank in late February, prompting repairs.

Adding the ISS astronaut crew swap to the mission requires extra cargo - in the form of Anderson's supplies - and handover activities to an already busy flight.

"When you rotate a crewmember, there's a significant amount of upmass in addition to that particular crewmember," Kirk Shireman, NASA's deputy ISS program manager at the agency's Houston-based Johnson Space Center, said last month. "There's their equipment, their [spacesuit], they have to have a special seat to fly home on the Soyuz...adding that additional mass is a hit, and adding handover activities is a timeline hit."

But after a detailed review Thursday morning, ISS mission managers decided they could in fact include the Expedition 15 astronaut crew swap during the STS-117 mission with no impact to shuttle of station mission objectives, Clem said.

Clayton, a 48-year-old native of Omaha, Nebraska, will make his first spaceflight during Expedition 15 and was slated to participate in the spacewalks planned for the STS-118 mission.

"He will continue to train for that because he will still be on station," Clem said.

Female spaceflight records

Waiting until August's STS-118 mission would have extended Williams' spaceflight by at least one month and given her the U.S. record for longest continuous spaceflight, which is currently held by her former crewmate - Expedition commander Michael Lopez-Alegria - who spent 215 days in orbit before returning to Earth on April 21.

Instead, Williams will return to Earth no earlier than June 19 after turning her Expedition 15 duties over to Anderson. Anderson, in turn, will be replaced by NASA astronaut Daniel Tani during the planned STS-120 shuttle mission to launch no earlier than Oct. 20. She currently holds the title for most spacewalks and spacewalking time - 29 hours and 17 minutes over four excursions - for a female astronaut.

Clem said Williams is now expected to spend about 192 days in space by her mission's end, which would set a new record for the longest single spaceflight by a female astronaut.

The current single-mission record by a female spaceflyer is held by NASA astronaut Shannon Lucid, who spent 188 days in orbit during a 1996 mission to Russia's Space Station Mir.