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 agiant robot, even as NASA struggles to provide crucial power to the device.
Clad inbulky spacesuits, spacewalkers Rick Linnehan and Garrett Reisman are slated tobegin the first of five planned excursions for their packed constructionmission at about 9:23 p.m. EDT (0123 GMT March 14). The spacewalking duo andfive other crewmates arrivedat the station aboard NASA?s shuttle Endeavour late Wednesday night tobegin a record-long stay at the orbital laboratory.
"As iftoday wasn't busy enough, tomorrow just gets harder," said Mike Moses,NASA's lead shuttle flight director for Endavour?s STS-123 mission, during apress briefing here at Johnson Space Center.
While twoastronauts prepare for their spacewalk, engineers on Earth are troubleshootinga strange power glitch with the platform containing the Canadian Space Agency?sDextre (pronounced ?Dexter?) maintenancerobot, which Linnehan and Reisman are expected to partly assemble later tonight.
LeRoy Cain,chair of NASA's mission management team, said that first tries to power up theplatform and robot pieces ? a step taken to keep the electronics warm andprotected from the harshness of space ? were not successful. Cain said,however, that the issue is likely to be worked around and that it will notsignificantly impact Linnehan and Reisman's orbital work.
"Thisis 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 dayswithout consequence. "There's not a great sense of urgency."
Spacestation flight director Ginger Kerrick said Thursday afternoon that the glitchcould be the result of a software hiccup, and Canadian engineers are drawing upa patch for the bug if the theory pans out. Other troubleshooting efforts couldprompt spacewalkers to inspect cable connections or grapple the Dextre robotwith the station?s robotic arm, which can also feed power to the massive,two-armed automaton.
?There?s alot more specialists that need to be called in,? Kerrick said.
Fondlyreferred to as "Mr. Dextre" or "Gigantor" by the STS-123crew, Dextre is an on-orbitservicing robot designed to cut down on the number of dangerous spacewalksastronauts perform.
"It?sthis giant robot with arms and ? wrists and hands," Linnehan said of thespecial-purpose dexterous manipulator (SPDM), as it is formally known.
One ofLinnehan and Reisman tasks during their 6.5-hour overnight spacewalk will be toattach 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 mobileplatform on the space station's Port 1 truss.
"It'sreally no small feat for a crewmember outside [the space station]," saidZebulon Scoville, lead spacewalk officer, of assembling Dextre's arms.
Thespacewalking duo's handiwork will leave Dextre a step closer to completion,which Linnehan, Behnken and Foreman will finish in pairs during two subsequentspacewalks.
Before theastronauts partially piece Dextre together, however, they will help prepare theJapaneseLogistics Pressurized (JLP) module for its voyage out of Endeavour'spayload bay. The module is the first piece of Japan?s massive laboratory calledKibo, which means ?Hope? in Japanese.
Immediatelyafter leaving the airlock, the spacewalkers will migrate to the payload bay andremove thermal covers that protected the JLP module during flight.
"Thenwe also have to unplug [an] electrical cable that is used to keep it warm whileit?s inside the payload bay," Reisman said, noting that he and Linnehanwill then begin the first leg of Dextre's assembly.
Bob Behnkenand Leopold Eyharts, robotic arm operators and STS-123 mission specialists,will then hoist the 9.2-ton cylindricalmodule that will serve primarily as extra space for the Japan AerospaceExploration Agency's Kibo laboratory.
"Idon?t mean to insult my own payload here," Reisman said, "[but] it?sreally just a closet of the Japanese laboratory."
As theorbital closet is delivered to the top of the Harmony module, where it willremain until STS-124 astronauts deliver its 37-foot (11-meter) counterpartcalled the Pressurized Module, Reisman said he may be a little distracted.
"We?llbe focused on our ? work, but out of the corner of our eye we?ll see themtaking this big module outside the payload bay," he said.
Tonight'sspacewalk is set to wrap up Friday morning around 3:53 a.m. EDT (0753 GMT), andwill 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 broadcastingEndeavour's STS-123 mission live on NASA TV. Click here for SPACE.com'sshuttle mission coverage and NASA TV feed.
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