ISS Astronauts Prepare for Launch and Landing

The twoastronauts aboard the International Space Station (ISS) are finalizing plansfor their Earth return while a fresh crew and Brazil's first spacefarer prepare tolaunch toward the orbital laboratory.

ISS Expedition12 commander BillMcArthur and flight engineer Valery Tokarev are stowing cargo and packing their bags inanticipation for an April 8 descent to Earth. The two men have spent nearly sixmonths aboard the space station to maintain its systems, conduct scienceexperiment and continue a chain of human spaceflight that has gone unbroken forfiveyears.

"It hasbeen a lot of hard work for the crew and the folks on the ground," saidExpedition 12 lead flight director Sally Davis Wednesday in a mission briefingat NASA's Johnson Space Center in Houston.

Thereplacement crew for McArthur and Tokarev, Expedition13 commander Pavel Vinogradovand flight engineer Jeffrey Williams, will launch toward the ISS on March 29EST with Brazilianastronaut Marcos Pontes, who will spend eight days aboard the station oncethe trio dock on March 31 EST, NASA officials said. A third ISS crewmember isslated to join the Expedition 13 in July, they added.

"I think thenumber one accomplishment of Expedition 13 is to get back to a complement ofthree crewmembers," said Kirk Shireman, NASA's ISSdeputy program director, during the briefing.

NASAofficials said an unexpected pair of problems with both Russian and U.S. spacesuit systems temporarily leftthe Expedition 12 crew unable to conduct spacewalks if the need arose.

McArthurand Tokarev have been unable to find air scrubbercanisters for the Russian-built Orlan spacesuitsaboard the ISS, while issues with U.S.-built station handrails prompted a holdon spacewalks in U.S. suits, Shiremansaid.

Thehandrail issue is expected to be resolved early Thursday, and additional Orlan air scrubbers will be launched toward the stationaboard the next unmanned Russian cargo ship next month, NASA officials said.

Mission's end approaches

McArthurand Tokarev have lived and worked aboard the ISSsince their arrivalon Oct. 3, 2005.

The two menhoped to host NASA's second post-Columbiaaccident shuttle flight, STS-121aboard the Discovery orbiter, as well as a third ISS crewmember in the form ofEuropean astronaut ThomasReiter. But delays have pushed that flight's launch, and Reiter's ISS trip,until noearlier than July 2006 during Expedition 13, NASA officials said.

But theExpedition 12 crewmembers were not left with idle time. With the station crewslimited to two astronauts - down from the typical three - NASA ISS flightcontrollers expected McArthur to spend a maximum of just nine hours a week onscience experiments.

However,the crew has managed to cram up to 13 hours a week of science studies, largelyby performing experiments during free time, said Pete Hasbrook,ISS Expedition 12 increment manager, in a mission briefing.

JulieRobinson, ISS Expedition 12 lead scientist, said McArthur has completed a boneand muscle study dubbed "Foot" that has been underway since the Expedition 6crew ran the station in 2002, and is the fourth of four participants in theexperiment. The study is aimed at understanding how the human body's musclesand bones deteriorate in the weightless environment, Robinson said.

"We'reexpecting to see some of the earlier results from the whole data set soon," sheadded.

In a first for ISS crews, McArthur and Tokarevhave performed two Soyuz relocation flights - thelatest on Monday - during their flight and have the honor of docking ateach of the station's Russian-built berths. They have also conducted twospacewalks to maintain the ISS - one in U.S.spacesuits and the other in Russian Orlan suits - which culminated with Tokarevsetting an unmannedOrlan adrift in space to be tracked by HAM radiooperators on Earth.

The twoastronauts were also greeted by Sir Paul McCartney during a liveconcert broadcast to the ISS last year.

McArthurhas earned a reputation for both tidiness and an eagerness to communicate hisspaceflight experience with the public.

"Bill iskind of Mr. Organized onboard," Hasbrook said, addingthat it is an open secret that he enjoys talking to Earth listeners via thestation's HAM radio. "He has spoken to 34 schools on his own time and more than1,500 contacts around the world. All of those numbers are records."

A newcrew prepares

Just asMcArthur and Tokarev are preparing to head back totheir home planet, three other astronauts are bracing themselves to leave terrafirma.

Pontes andthe Expedition 13 crew are slated to launch spaceward aboard their Soyuz TMA-8spacecraft on March 29 at 9:30 p.m. EST (0230 March 30 GMT) on a two-daytrip to the ISS. Earlier this week, the astronauts donned their Russian-built Sokol spacesuits for fit checks inside their Soyuz vehicleat Baikonur Cosmodrome inthe Kazakhstan.

"We'reexcited about having our third crewmember on board, so it's a very importantincrement to us," Shireman said of Expedition 13.

Pontes willmake history as Brazil's first astronaut to fly, and hasbeen training for his flight since 1998. He will spend about eight days aboardthe ISS conducting nanotechnology experiments before returning to Earth withthe Expedition 12 crew, he has said.

Meanwhile,the Expedition 13 crew has a busy six months ahead.

Vinogradovand Williams anticipate not one, but two possible shuttle visits to thestation. In addition to the STS-121 crew and Reiter's arrival in July, the crewmay 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 noearlier than Aug. 28, NASA has said.

In betweenthose flights are two spacewalks, the first for Williams and Reiter in U.S. spacesuits, and the other for Vinogradov and Williams in Orlansuits. The crew must also prepare for the April arrival of an unmanned RussianProgress supply ship.

NASAofficials are also completing studies to make sure that a golf stunt, in which Vinogradov will smack a golf ball off the ISS during aspacewalk as part of a commercial agreement, is safe.

"As agolfer, I'm interested in it too," Shireman said."But we're absolutely going to make sure it's safe before we go ahead."

• Space Station Crew Takes Short Soyuz Trip
• Russian Spacecraft Vital to Boost ISS Crew Size
• Complete Coverage: ISS Expedition 12
• Complete Coverage: ISS Expedition 13