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.
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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