This
story was updated at 11:59 p.m.
HOUSTON --
The International Space Station (ISS) unfurled a shiny new set of solar wings
Tuesday to increase its power supply and support future construction.
Astronauts
aboard the ISS and NASA's shuttle Atlantis watched as the new solar arrays at
the tip of the station's new
Starboard 3/Starboard 4 (S3/S4) truss unfolded like window blinds as
the two spacecraft flew 214 miles (344 kilometers) above Earth.
"Everything
worked as expected and we ended up with two brand new solar arrays," Atlantis
astronaut Jim Reilly II said after the successful deployment.
The new
solar wings are the third of four U.S.-built arrays to be installed at the
ISS and were attached to the orbital laboratory during a Monday spacewalk. They
will allow the orbital laboratory to power new modules and
international laboratories from Europe and Japan, which are slated to
launch towards the ISS later this year and in early 2008.
"So
they need electricity for those new modules, and that's part of our job, to
allow them to have that," said Atlantis astronaut Steven Swanson, an
STS-117 mission specialist, in a NASA interview.
The solar
arrays' S4 truss is designed to rotate its power-generating wings like a
paddlewheel so they can track the Sun and maximize electricity production. But
first, an older solar array wing extending over the new S3/S4 trusses from the
station's mast-like Port 6 (P6) truss will
have to be retracted to clear the area.
That solar
array retraction is planned during a Wednesday spacewalk by Swanson and fellow
STS-117 astronaut Patrick Forrester. The astronauts launched towards the ISS
aboard Atlantis on June 8 to deliver the new starboard solar arrays, trusses
and a new crewmember to the ISS during their 13-day mission.
Slow and
steady
The space station's
new solar wings began to unfold in earnest at about 4:03 a.m. EDT (0803 GMT),
while the ISS and shuttle astronauts slept, when flight controllers on Earth
commanded the first of the two solar wings to extend
a single mast section, or bay, of its 31.5-bay length.
"It's
really good to look out and see the solar array blankets extended one bay,"
STS-117 mission commander Rick Sturckow said.
By 1:58
p.m. EDT (1759 GMT), both solar arrays were fully deployed.
Each ISS
solar wing is made up of two 115-foot (35-meter) panels attached to a central
mast. When fully unfurled, their wingspan reaches 240 feet (73 meters) from tip
to tip.
Both arrays
were deployed in stages, which allowed sunlight to warm them up and avoid their
paper-thin photovoltaic cells from sticking to one another too strongly -- a
phenomena known as 'stiction' -- after years of being packed in a box about 20
inches (50 centimeters) deep.
When NASA
deployed its first pair of U.S. solar arrays from the station's P6 truss during
the STS-97 mission in 2000, the panels encountered severe stiction and a
tension line came off its spool, prompting a spacewalk repair.
Tuesday's
solar array deployment, by comparison, appeared to go smoothly.
A navigation
computer issue in the station's Russian-built segment forced the orbital
laboratory to switch between its own U.S. gyroscopes and the Atlantis shuttle's
thrusters to maintain attitude control, leading to some delays in fully
charging the new solar wings and impacting the power produced by their older
port-side counterparts. But by late Tuesday, the system was back online and the
new arrays charging properly, NASA officials said.
Meanwhile,
the Atlantis astronauts had some free time Tuesday before gearing up for
Wednesday's spacewalk.
Swanson and
Forrester will perform the second of four planned spacewalks for the STS-117
mission during the excursion, and will spend the night in the station's
Quest airlock to cut down on the time required to prepare their bodies for the
planned 6.5-hour excursion.
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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