Encyclopedia Astronautica
2006.09.15 - STS-115 MCC Status Report #12


The Atlantis and International Space Station crews today will focus on the third and final spacewalk of the mission.

The STS-115 crew, Commander Brent Jett, Pilot Chris Ferguson and Mission Specialists Dan Burbank, Joe Tanner, Heide Stefanyshyn-Piper and Steve MacLean, is in its fourth day of joint operations with the station crew. Their Expedition 13 counterparts, Commander Pavel Vinogradov and Flight Engineers Jeff Williams and Thomas Reiter, will support the spacewalk activities as well as continued space station operations and maintenance.

Both crews awoke at 11:15 p.m. CDT to "Hotel California" performed by the Eagles and played for Tanner.

Tanner and Stefanyshyn-Piper will team up again for the spacewalk. While they were in the Quest airlock preparing for the spacewalk, a circuit-breaker-like remote power controller (RPC) tripped, causing loss of power to the airlock's depressurization pump. While flight controllers and engineers assessed the cause of the problem, the spacewalkers moved to the adjacent Unity module, while continuing to breathe oxygen through masks per their pre-spacewalk protocol.

The trip of the RPC was apparently due to a momentary spike in the electrical current of the depressurization pump. After assessing data to ensure the system had no short circuit, the breaker was reset and pump reactivated. Tanner and Stefanyshyn-Piper are scheduled to leave the Quest airlock at about 4:15 a.m. Once the spacewalk begins, the two will split up to perform the scheduled tasks for the spacewalk.

Tanner will install bolt retainers on the P6 Beta Gimbal Assembly, which helps to orient the pitch of the solar array wings. He’ll also use a new technique to attempt to re-engage a four-bar hinge lock that did not properly engage during STS-97.

Meanwhile, Stefanyshyn-Piper will retrieve the Materials on the International Space Station Experiment 5. The materials science experiment tests the effects of the space environment on prospective spacecraft materials.

The two will then prepare the photovoltaic radiator for deployment by removing launch hardware that was in place to protect it during the shuttle launch. Once that is done, other crewmembers can deploy that heat-dissipating radiator. Next the spacewalkers will replace an S-band antenna support assembly (SASA) on the Starboard 1 (S1) truss. They’ll also install a shroud on the failed SASA, which will be returned to Earth on a later mission.

Dividing again, Stefanyshyn-Piper will replace a baseband signal processor and transponder on S1 and Tanner will install a heat shield onto an antenna group interface tube to help overheating in this area during certain vehicle attitudes.

They’ll wrap up the spacewalk with two new tasks, installing a new external wireless television antenna and performing a Detailed Test Objective to assess infrared video of the wing leading edge. The spacewalk is scheduled to last 6.5 hours.

Once the spacewalk is completed, the mobile transporter, a movable platform that moves along the truss segments, will be relocated to a position on the newly arrived P3 truss to check out that worksite.

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