HOUSTON -- Astronauts
aboard the International Space Station (ISS) will physically unplug a pair of
cables feeding power from new solar arrays to the outpost's Russian segment late Thursday
in hopes that it might aid the recovery of critical computer systems, mission
managers said.
"The
leading theory today is, we've introduced some noise at a level that, now, these
computers are tripping themselves off," NASA ISS program manager Mike
Suffredini said.
The
German-built computers used in the station's Russian segment are known to be
susceptible radiant or conductive "noise" in power feeds, which led ISS
engineers to suspect that a similar phenomenon may be at work in cables ferrying
power from the station's
new solar arrays at the tip of the Starboard 4 power truss installed
earlier this week.
"It seems
that shortly after we made those connections our Russian colleagues started
having problems," Suffredini said, adding that, if proven, it would hint at
some anomaly in the new solar wings. "The power source coming from the solar
arrays that have been on orbit has been very clean, if you will. We've been
well within our power quality specs."
The theory
is by no means final, but will be tested along with others to determine exactly
what prompted a
major shutdown of the station's Russian computer systems Wednesday. The
shutdown left the ISS dependent on U.S. attitude control systems and thrusters
aboard the visiting Atlantis shuttle.
NASA
officials expect the troubleshooting efforts to
run several days, and hope to recovery the computer systems before Atlantis
leaves the ISS on June 19.
"We do
these things one step at a time," Suffredini said. "We try not to shotgun these
fixes."
To test the
possible fix, astronauts will open up access panels in the station's Unity
node, then manually disconnect cables that feed S4 solar array power into
converters that, in turn, route it into the Russian modules. The modules will
rely on a previous power configuration to draw electricity generated by solar
arrays at the portside end of the ISS, Suffredini said.
"This sounds
like a good plan," said Atlantis mission specialist Sunita Wiliams, who until recently
served as an ISS crewmember, after Mission Control relayed it to the station
crew today. "We're looking forward to trying to get these computers back
online."
Some of the
station's Expedition 15 crew will have to wake up overnight to aid Russian flight
controllers in troubleshooting the computer glitch. The work has affected the crew's
sleep schedule since it can only be done when the ISS passes over Russian ground
stations early in the day, NASA said.
Meanwhile,
Atlantis shuttle astronauts spent much of today preparing for a Friday
spacewalk and continuing efforts to furl an old solar array reaching out to
starboard from the space station's mast-like Port 6 (P6) truss.
Atlantis'
STS-117 mission specialists Jim Reilly II and Danny Olivas will step outside
the ISS Friday to repair
a torn heat shield blanket on the orbiter's aft, install a vent valve for a
new ISS oxygen system and help coax a stubborn
solar array into its storage boxes atop the space station's mast-like Port
6 truss.
Efforts to
retract the solar array, which was partly furled during a Wednesday spacewalk, met
some additional success today as astronauts remotely guided a few more sections
into storage boxes. About half of the array's 115-foot (35-meter) length
remains to be packed away during Friday's spacewalk.
"That's
good news," said NASA astronaut Megan McArthur, serving as spacecraft
communicator in Mission Control. "We're halfway there."
NASA is
broadcasting the space shuttle Atlantis' STS-117 mission live on NASA TV. Click here for mission updates and
SPACE.com's video feed.
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