Encyclopedia Astronautica
2007.06.12 - STS-117 MCC Status Report #09


The International Space Station today spread its wings again with the activation of a new pair of solar arrays that will generate enough power to supply about eight homes.

The extra power sets the stage for addition of European and Japanese laboratories later this year and early next.

Prior to crew wake up this morning, station controllers began unfurling the solar array attached to the newly installed S3/S4 truss segment. Space Shuttle Atlantis astronauts then took over, unfolding one wing at a time in stages, pausing to let the solar array panels soak up some sun, which helps to prevent the thin individual panels from sticking together. They finished unfolding the first wing at 11:29 a.m. and the second at 12:58 p.m. – both are now capable of generating power.

Tomorrow at about 1 p.m., Mission Specialists Patrick Forrester and Steve Swanson head outside on their first of two spacewalks to remove launch locks from the 10-foot-wide solar alpha rotary joint to free the arrays to rotate and track the sun. During the six-hour spacewalk, the spacewalkers will help flight controllers fold up an older solar array to make room for the rotation. That retracted pair of arrays and corresponding truss segment eventually will be relocated and redeployed to add even more power capability to the station.

Late in the day, the station experienced a problem with a Russian navigation computer that challenged flight controllers in Houston and Moscow to manage the station’s attitude in space. Several methods of attitude control are available – Russian thrusters, Atlantis thrusters, or station electrically-driven gyroscopes.

The crew or station never was in danger throughout the troubleshooting efforts, and the station’s gyroscopes took over attitude control shortly after 8 p.m. That was followed by relocation of the Mobile Transporter in preparation ahead of tomorrow’s spacewalk.

The problem with the navigation computer began when flight controllers attempted to turn attitude control over to the station computers after letting shuttle computers handle it while the arrays were unfolded. The computer would not allow them to do so, and forced a reboot of the main Russian command and control computer, which triggered an alarm enunciating the problem to the crew and ground controllers.

Meanwhile, mission managers still are mulling over the best course of action for repairing a raised corner of a thermal insulation blanket that came loose during launch last Friday. The Mission Management Team elected to wait at least one more day so that engineers could develop detailed plans for a spacewalking task to be carried out during the third or fourth spacewalk (Friday or Sunday).

Ground tests will be performed to understand which repair technique provides the greatest potential for success.

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