This story was updated at 6:35 p.m. ET.
HOUSTON -
Two astronauts will venture outside the International Space Station (ISS)
tonight to help deliver Japan's first orbital room and begin constructing a
giant robot, even as NASA struggles to provide crucial power to the device.
Clad in
bulky spacesuits, spacewalkers Rick Linnehan and Garrett Reisman are slated to
begin the first of five planned excursions for their packed construction
mission at about 9:23 p.m. EDT (0123 GMT March 14). The spacewalking duo and
five other crewmates arrived
at the station aboard NASA's shuttle Endeavour late Wednesday night to
begin a record-long stay at the orbital laboratory.
"As if
today wasn't busy enough, tomorrow just gets harder," said Mike Moses,
NASA's lead shuttle flight director for Endavour's STS-123 mission, during a
press briefing here at Johnson Space Center.
While two
astronauts prepare for their spacewalk, engineers on Earth are troubleshooting
a strange power glitch with the platform containing the Canadian Space Agency's
Dextre (pronounced "Dexter") maintenance
robot, which Linnehan and Reisman are expected to partly assemble later tonight.
Power
problems
LeRoy Cain,
chair of NASA's mission management team, said that first tries to power up the
platform and robot pieces — a step taken to keep the electronics warm and
protected from the harshness of space — were not successful. Cain said,
however, that the issue is likely to be worked around and that it will not
significantly impact Linnehan and Reisman's orbital work.
"This
is a problem we don't need a solution for right this hour or this day,"
Cain said, noting that Dextre's heaters can remain un-powered for several days
without consequence. "There's not a great sense of urgency."
Space
station flight director Ginger Kerrick said Thursday afternoon that the glitch
could be the result of a software hiccup, and Canadian engineers are drawing up
a patch for the bug if the theory pans out. Other troubleshooting efforts could
prompt spacewalkers to inspect cable connections or grapple the Dextre robot
with the station's robotic arm, which can also feed power to the massive,
two-armed automaton.
"There's a
lot more specialists that need to be called in," Kerrick said.
Space-age
robot
Fondly
referred to as "Mr. Dextre" or "Gigantor" by the STS-123
crew, Dextre is an on-orbit
servicing robot designed to cut down on the number of dangerous spacewalks
astronauts perform.
"It's
this giant robot with arms and ... wrists and hands," Linnehan said of the
special-purpose dexterous manipulator (SPDM), as it is formally known.
One of
Linnehan and Reisman tasks during their 6.5-hour overnight spacewalk will be to
attach each of Dextre's 115-pound (52-km) hands its respective, 662-pound
(300-km) arm. They'll fully assemble the massive robot arms on a mobile
platform on the space station's Port 1 truss.
"It's
really no small feat for a crewmember outside [the space station]," said
Zebulon Scoville, lead spacewalk officer, of assembling Dextre's arms.
The
spacewalking duo's handiwork will leave Dextre a step closer to completion,
which Linnehan, Behnken and Foreman will finish in pairs during two subsequent
spacewalks.
Before the
astronauts partially piece Dextre together, however, they will help prepare the
Japanese
Logistics Pressurized (JLP) module for its voyage out of Endeavour's
payload bay. The module is the first piece of Japan's massive laboratory called
Kibo, which means "Hope" in Japanese.
Orbital
closet
Immediately
after leaving the airlock, the spacewalkers will migrate to the payload bay and
remove thermal covers that protected the JLP module during flight.
"Then
we also have to unplug [an] electrical cable that is used to keep it warm while
it's inside the payload bay," Reisman said, noting that he and Linnehan
will then begin the first leg of Dextre's assembly.
Bob Behnken
and Leopold Eyharts, robotic arm operators and STS-123 mission specialists,
will then hoist the 9.2-ton cylindrical
module that will serve primarily as extra space for the Japan Aerospace
Exploration Agency's Kibo laboratory.
"I
don't mean to insult my own payload here," Reisman said, "[but] it's
really just a closet of the Japanese laboratory."
As the
orbital closet is delivered to the top of the Harmony module, where it will
remain until STS-124 astronauts deliver its 37-foot (11-meter) counterpart
called the Pressurized Module, Reisman said he may be a little distracted.
"We'll
be focused on our ... work, but out of the corner of our eye we'll see them
taking this big module outside the payload bay," he said.
Tonight's
spacewalk is set to wrap up Friday morning around 3:53 a.m. EDT (0753 GMT), and
will enable Doi and Linnehan to begin outfitting the JLP module.
SPACE.com Senior Editor Tariq Malik contributed to this report from New York City.
NASA is broadcasting
Endeavour's STS-123 mission live on NASA TV. Click here for SPACE.com's
shuttle mission coverage and NASA TV feed.
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