Mission Specialists Bill McArthur and Leroy Chiao will connect two sets of cables to provide power to heaters and conduits located on the Z1 truss, relocate two communication antenna assemblies and install a toolbox for use during future on-orbit construction. The space walk is scheduled to begin about 9:45 this morning. Japanese Astronaut Koichi Wakata will once again be at the controls of the shuttle's robotic arm, using it to move the two astronauts around Discovery's payload bay and the space station.
Chiao, designated EV1 and recognizable by the red bands on the legs of his spacesuit, and McArthur, designated EV2 in a solid white suit, will devote the first hour of their space walk to set-up activities in Discovery's payload bay, deploying tools and EVA aids including foot restraints and tethers. With that complete, the first task will be to connect the first six umbilical cables between Unity and the truss structure. To ensure that the connectors the astronauts will be working with are not "hot," International Space Station controllers in Houston and Moscow will alternately power down two Russian-to-American Conversion Units, called RACUs. They provide power to some of the systems in the Unity module including the early communication system and some cabin fans. RACU 5 will be powered down to support the first cable installation and reactivated before the power down of RACU 6, ensuring that the Unity module will not be without power during the space walk activities.
A second set of four umbilical power cables will be connected later in the space walk once RACU 5 has been repowered, and RACU 6 deactivated.
Following the first cable installation task, McArthur and Chiao will remove the S-band Antenna Subassembly (SASA) from its launch position on the Z1 truss and place it in a temporary location until it is moved and activated during the STS-97 mission in late November. The SASA is launched in the position where two power conditioning systems - called DDCU-HPs - will be installed during their space walk on Tuesday. McArthur and Chiao will then turn their attention to installing the Space to Ground Antenna (SGANT) deploying its antenna dish. The antenna dish will be removed from its launch location on the Z1 truss with Chiao standing on the robotic arm as McArthur unbolts the dish assembly. Because of thermal limitations, the antenna dish needs to be attached to the boom assembly within an hour after being removed from its launch location.
McArthur and Chiao also will relocate a tool stowage box, located on the support structure for PMA-3 in Discovery's payload bay, for use during future on-orbit construction activities before concluding their space walk and climbing back into Discovery's airlock.
Throughout the EVA, the second team of space walkers on this flight, Jeff Wisoff and Mike Lopez-Alegria, will act as in-cabin choreographers providing guidance and assistance to McArthur and Chiao and back-up support to robot arm operator Wakata.
Following the conclusion of the space walk, McArthur, Chiao, Wisoff and Lopez-Alegria will resize the spacesuits, recharging batteries and preparing them for the second of four consecutive days of EVAs to expand the International Space Station.