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."
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