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| Image above: This image depicts the current configuration
of the International Space Station following the partial retraction
of the P6 port solar array. Image Credit: NASA |
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SARJ takes charge as arrays track the sun
The International Space Station’s newest set of solar arrays is
tracking the sun tonight, following partial retraction of a similar array
that’s been the station’s primary power plant for six years.
This event sets the stage for two challenging spacewalks by the STS-116
crew to rewire and reroute the station’s power system.
The Solar Alpha Rotary Joint (SARJ) and the new set of arrays are a part
of the P3/ P4 truss segments that were installed onto the station in September
during the STS-115 mission. The rotary joint enables the solar arrays
to follow the sun and generate the maximum power possible. Activation
of the SARJ occurred shortly before 8 p.m. EST, and a few minutes later
the Mission Control Center in Houston notified the crew that the arrays
were following the sun.
Throughout the day, the STS-116 crew and flight controllers worked together
to solve problems that prevented the P6 truss port solar arrays from folding
properly. The retraction activities of the arrays began at 1:28 p.m. More
than 40 commands were sent to furl and unfurl the arrays in an attempt
to properly align them. When the efforts concluded about 7:50 p.m., 13.5
of 31 bays had been folded, leaving the port arrays in a safe position
that allowed the activation of the P4 rotary joint.
The crew also received word that Thursday’s spacewalk will take
place as planned despite the problems retracting the P6 solar array. Mission
Specialists Bob Curbeam and Christer Fuglesang, KE5CGR, who conducted
the mission’s first spacewalk, are scheduled to begin Thursday’s
orbital stroll at 3:12 p.m. They will begin efforts to rewire the station,
bringing power generated by the P4 arrays on line for use by the station's
systems and prepare for more arrays to be added next year.
In preparation for the spacewalk, Curbeam and Fuglesang will again "campout"
in the station’s airlock. The pressure will be lowered in the airlock
to the pressure normally found on Earth 10,000 feet above sea level during
the overnight campout. The procedure protects against decompression sickness
as Curbeam and Fuglesang go to the even lower pressure of spacesuits on
Thursday.
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