The third spacewalk of Discovery's mission to the International Space Station is scheduled to begin at 1:37 p.m. CST to complete the rewiring of the orbiting laboratory's power system.
Discovery Mission Specialist Bob Curbeam and station Flight Engineer Sunita Williams will venture outside to finish the job started on Thursday's spacewalk. Station flight controllers will begin commanding about half of the station's systems to power down at about 10:52 a.m. CST. After Mission Control has cut the power on the two station electrical channels that are the subject of today's work, channels 1 and 4, the spacewalkers will rewire them. Completing that task will put the station power system in its permanent configuration, ready for more solar arrays and laboratories to be added in 2007.
Curbeam and Mission Specialist Christer Fuglesang, a European Space Agency astronaut from Sweden, completed a rewiring job on the other two station power channels, channels 2 and 3, during a spacewalk on Thursday.
Additional tasks for today's spacewalk include relocating debris shield panels from the station's interior to a storage point outside. The panels, designed to increase the protection of the station's Zvezda living quarters module, will be installed during a later spacewalk by the station crew. Curbeam and Williams also will install a robotic arm grapple fixture.
Today's spacewalk is planned to be completed at 7:47 p.m. CST, but can go longer if needed. If time allows after all originally planned tasks are completed during the excursion, one or both of the spacewalkers will move up the P6 truss atop the station to the base of its partially retracted port solar wing. From that point, they will push on a blanket box into which the array has been folding to attempt to jiggle apparently misaligned guide wires and grommets into place. The result may allow additional retraction of the array.
Meanwhile, managers are continuing to evaluate a possible fourth spacewalk that would take place on Monday to attempt to fully retract the array. However, no decision has been made regarding whether that spacewalk will be pursued. To prepare for that possibility, the spacewalkers today may bring several tools inside the station that would need to be prepared with insulating tape for use on a fourth spacewalk.
The transfer of equipment and supplies between the two spacecraft continues. Late Friday, the crews were slightly ahead of the transfer schedule.
Inside the station today, station Commander Michael Lopez-Alegria and Flight Engineer Mikhail Tyurin will replace a component of the orbiting laboratory's carbon dioxide removal system to restore it to full operation.
The orientation of the shuttle and station is again being controlled by the station's control moment gyroscopes. Small shuttle thrusters had been controlling the orientation of the spacecraft since Friday, when an initial attempt to switch to gyroscope control was not successful. A second attempt Saturday worked. Flight controllers believe the difficulty was due to increased atmospheric drag resulting from recent solar activity.
Shuttle crewmembers Commander Mark Polansky, Pilot Bill Oefelein and Mission Specialists Nicholas Patrick, Curbeam, Fuglesang, Joan Higginbotham and Thomas Reiter, along with Williams in the airlock campout, were awakened at 8:52 a.m. CST to composer Aaron Copeland's ?Fanfare for the Common Man,? performed by the London Philharmonic Orchestra. The music was played for Patrick.
The next STS-116 status report will be issued Friday evening or earlier if events warrant.
