The two astronauts aboard the International Space Station (ISS) are finalizing plans for their Earth return while a fresh crew and Brazil's first spacefarer prepare to launch toward the orbital laboratory.
ISS Expedition 12 commander Bill McArthur and flight engineer Valery Tokarev are stowing cargo and packing their bags in anticipation for an April 8 descent to Earth. The two men have spent nearly six months aboard the space station to maintain its systems, conduct science experiment and continue a chain of human spaceflight that has gone unbroken for five years.
"It has been a lot of hard work for the crew and the folks on the ground," said Expedition 12 lead flight director Sally Davis Wednesday in a mission briefing at NASA's Johnson Space Center in Houston.
The replacement crew for McArthur and Tokarev, Expedition 13 commander Pavel Vinogradov and flight engineer Jeffrey Williams, will launch toward the ISS on March 29 EST with Brazilian astronaut Marcos Pontes, who will spend eight days aboard the station once the trio dock on March 31 EST, NASA officials said. A third ISS crewmember is slated to join the Expedition 13 in July, they added.
"I think the number one accomplishment of Expedition 13 is to get back to a complement of three crewmembers," said Kirk Shireman, NASA's ISS deputy program director, during the briefing.
NASA officials said an unexpected pair of problems with both Russian and U.S. spacesuit systems temporarily left the Expedition 12 crew unable to conduct spacewalks if the need arose.
McArthur and Tokarev have been unable to find air scrubber canisters for the Russian-built Orlan spacesuits aboard the ISS, while issues with U.S.-built station handrails prompted a hold on spacewalks in U.S. suits, Shireman said.
The handrail issue is expected to be resolved early Thursday, and additional Orlan air scrubbers will be launched toward the station aboard the next unmanned Russian cargo ship next month, NASA officials said.
Mission's end approaches
McArthur and Tokarev have lived and worked aboard the ISS since their arrival on Oct. 3, 2005.
The two men hoped to host NASA's second post-Columbia accident shuttle flight, STS-121 aboard the Discovery orbiter, as well as a third ISS crewmember in the form of European astronaut Thomas Reiter. But delays have pushed that flight's launch, and Reiter's ISS trip, until no earlier than July 2006 during Expedition 13, NASA officials said.
But the Expedition 12 crewmembers were not left with idle time. With the station crews limited to two astronauts - down from the typical three - NASA ISS flight controllers expected McArthur to spend a maximum of just nine hours a week on science experiments.
However, the crew has managed to cram up to 13 hours a week of science studies, largely by performing experiments during free time, said Pete Hasbrook, ISS Expedition 12 increment manager, in a mission briefing.
Julie Robinson, ISS Expedition 12 lead scientist, said McArthur has completed a bone and muscle study dubbed "Foot" that has been underway since the Expedition 6 crew ran the station in 2002, and is the fourth of four participants in the experiment. The study is aimed at understanding how the human body's muscles and bones deteriorate in the weightless environment, Robinson said.
"We're expecting to see some of the earlier results from the whole data set soon," she added.
In a first for ISS crews, McArthur and Tokarev have performed two Soyuz relocation flights - the latest on Monday - during their flight and have the honor of docking at each of the station's Russian-built berths. They have also conducted two spacewalks to maintain the ISS - one in U.S. spacesuits and the other in Russian Orlan suits - which culminated with Tokarev setting an unmanned Orlan adrift in space to be tracked by HAM radio operators on Earth.
The two astronauts were also greeted by Sir Paul McCartney during a live concert broadcast to the ISS last year.
McArthur has earned a reputation for both tidiness and an eagerness to communicate his spaceflight experience with the public.
"Bill is kind of Mr. Organized onboard," Hasbrook said, adding that it is an open secret that he enjoys talking to Earth listeners via the station's HAM radio. "He has spoken to 34 schools on his own time and more than 1,500 contacts around the world. All of those numbers are records."
A new crew prepares
Just as McArthur and Tokarev are preparing to head back to their home planet, three other astronauts are bracing themselves to leave terra firma.
Pontes and the Expedition 13 crew are slated to launch spaceward aboard their Soyuz TMA-8 spacecraft on March 29 at 9:30 p.m. EST (0230 March 30 GMT) on a two-day trip to the ISS. Earlier this week, the astronauts donned their Russian-built Sokol spacesuits for fit checks inside their Soyuz vehicle at Baikonur Cosmodrome in the Kazakhstan.
"We're excited about having our third crewmember on board, so it's a very important increment to us," Shireman said of Expedition 13.
Pontes will make history as Brazil's first astronaut to fly, and has been training for his flight since 1998. He will spend about eight days aboard the ISS conducting nanotechnology experiments before returning to Earth with the Expedition 12 crew, he has said.
Meanwhile, the Expedition 13 crew has a busy six months ahead.
Vinogradov and Williams anticipate not one, but two possible shuttle visits to the station. In addition to the STS-121 crew and Reiter's arrival in July, the crew may also welcome the STS-115 construction flight aboard Atlantis. That mission, which would deliver a new set of solar arrays to the ISS, is set to launch no earlier than Aug. 28, NASA has said.
In between those flights are two spacewalks, the first for Williams and Reiter in U.S. spacesuits, and the other for Vinogradov and Williams in Orlan suits. The crew must also prepare for the April arrival of an unmanned Russian Progress supply ship.
NASA officials are also completing studies to make sure that a golf stunt, in which Vinogradov will smack a golf ball off the ISS during a spacewalk as part of a commercial agreement, is safe.
"As a golfer, I'm interested in it too," Shireman said. "But we're absolutely going to make sure it's safe before we go ahead."