Two
astronauts living aboard the International Space Station (ISS) are preparing to
fling an empty spacesuit into orbit next week during the second spacewalk of
their six-month mission.
ISS Expedition
12 commander Bill McArthur and flight engineer Valery Tokarev will step
outside their orbital laboratory on Feb. 3 in a spacewalk that calls for -
among other things - deploying a human-shaped satellite into a short-lived
orbit.
McArthur
and Tokarev will launch an unmanned, radio-equipped "SuitSat" spacesuit-
the same Russian-built Orlan space attire they will don for the extravehicular
activity (EVA) - and perform a series of maintenance tasks during the planned
six-hour spacewalk. [Click here for
more on the SuitSat experiment.]
"The crew
is in great spirits and is very eager to participate in this [spacewalk]," said
Kwatsi Alibaruho, NASA's Expedition 12 EVA flight director, during a Friday
press briefing at the agency's Johnson Space Center in Houston, Texas.
The coming EVA
will mark the fourth career spacewalk for McArthur and the second for Tokarev.
Spacesuit toss, mobile transporter and more
The SuitSat
toss is, by far, the most eye-catching tasks planned for the upcoming
spacewalk.
McArthur
and Tokarev have primed the Orlan spacesuit with an antenna, radio transponder
and other gear for its brief mission. Tokarev will toss the unpressurized garment
into space in a retrograde direction -opposite of the space station's flight
path - where it will orbit for several days before burning up in the Earth's atmosphere.
"A lot of
students are really excited and awaiting the SuitSat signal," said NASA's
Expedition 12 lead scientist Julie Robinson.
SuitSat
will broadcast a repeating message in five languages, as well as an image and
several "secret words" for listening students to decode on Earth, NASA
officials said, adding that the experiment is sponsored by a collection of international
ham radio operators.
Following
the SuitSat deployment, the McArthur and Tokarev will move a hub cap-sized grappling
fixture used by the station's Russian Strela boom from its current location on
the Zarya control module to the Pressurized Mating Adapter-3 (PMA-3) docking
port, where NASA orbiters typically berth. The boom will be moved there later
for a future spacewalk.
One vital
task involves the space station's mobile transporter, a platform designed to traverse
up and down the laboratory's main truss like a railcar.
Last month,
a cutter tool inadvertently sliced one of two trailing umbilical system (TUS) cables
that transfer power, data and video imagery to and from the mobile transporter.
The cutter tool, part of the Interface Assembly Unit (IAU), is designed to
slice away utility cables should they snag during critical operations, such as
spacecraft dockings, NASA officials said.
"It's
essentially a guillotine," said Kirk Shireman, NASA's deputy ISS program
manager at JSC, of the cutter during the briefing. "It's really important that
we fix this before we can use the mobile transporter."
The mobile
transporter, which serves as a base for the station's robotic arm and a sled
for major ISS components, cannot be used for either function until it has both
cable systems in operation.
McArthur
and Tokarev will safeguard the working cable from inadvertently being cut by
installing a special safing bolt. But a future spacewalk during the next
shuttle mission - NASA's STS-121
flight set for May - will be needed to swap out the problematic IAU, ISS
managers said.
Prep
work
To prepare
for their spacewalk, the Expedition 12 crew has spent many hours going over
details with flight controllers, cataloging tools, sifting through images and
watching video beamed up to the station from mission control.
"It's been
six months since their last water run training EVA and three months since their
last spacewalk,
which can have some effect on efficiency," said Anna Jarvis, the lead
Expedition 12 EVA officer at NASA's Johnson Space Center in Houston, Texas, during
the briefing. "But [ISS] increment crews have an advantage that they have
adapted themselves to moving in the weightless environment."
The
astronauts are also slated to conduct a photographic survey of the station's
Russian-built service module and retrieve a Russian Biorisk container designed
to study the space environment's impact on microorganisms.
"By the
conclusion of this EVA, Bill and Valery will have traversed to just about the
extreme ends of every part of the station, which I know [they] are looking
forward to," Jarvis explained.
Space
station science
In addition
to his spacewalk preparation and maintenance tasks, McArthur has thrived in his
role as NASA's ISS Science Officer, Robinson said.
The
astronaut veteran has spent his personal time on Saturdays as a human
centrifuge, spinning in circles to try to eliminate bubbles from cell growth
sample containers, she added.
McArthur
has also relayed more than 8,000 images down to flight controllers and
performed a series of studies to test capillary action, the behaviors of
materials that hover between liquids and gases, as well as the responses of his
own legs and feet - and their respective muscles - to the microgravity
environment. He and Tokarev have also performed the second of three kidney
stone studies of their mission.
By the time
of their second spacewalk, McArthur and Tokarev will have lived aboard the ISS
for four months since docking
at the station on Oct. 3, 2005. The two men are expected to return to Earth on
April 9 with Brazilian astronaut Marcos
Pontes, who will launch toward the space station with ISS
Expedition 13 commander Pavel Vinogradov and flight engineer Jeffrey
Williams on March 30.
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