In what have been termed "clear the deck" tasks by lead EVA Officer Darryl Schuck, Lopez-Alegria and Wisoff, with an assist from robot arm operator, Koichi Wakata, will remove a grapple fixture from the Z1 Truss, verify the operation of the latch assembly that will capture the solar array truss when it arrives in December, deploy a tray that will be used to provide power to the U.S. Laboratory "Destiny" when it arrives early next year, and test the performance of the manual berthing mechanism latches that will support Destiny.
If time permits, the space walkers will also evaluate two safety protocols - testing a small nitrogen-powered back pack that could allow astronauts to navigate back to the station or shuttle in the event their safety tethers became disconnected, and demonstrating techniques for assisting an incapacitated astronaut during a space walk.
Lopez-Alegria, Wisoff and Wakata will team up to deploy the Z1 tray, as Lopez-Alegria on the robot arm holds the tray in place while Wisoff removes a total of four pins and then raises the tray from its position on the truss. Lopez-Alegria will guide the tray into its fully deployed position and will hold it in place to allow Wisoff to install the pins and latches that will hold it in place.
Wisoff will cycle the latches on the capture assembly for the solar arrays by using a pistol grip tool and making more than 125 turns to open the latches. He will then close and reopen the latches to ensure they are working properly and will leave the RTAS capture latch - known as "the claw" - ready to support the installation of the P6 solar arrays by the STS-97 crew in December. He also will verify the operation of the manual berthing mechanism capture system on the truss that will be used during installation of the Destiny laboratory module early next year.
Following today's space walk, Commander Brian Duffy and Pilot Pam Melroy will once again pulse Discovery's reaction control system jets in a series of small firings to gently raise the station's orbit to prepare it for the arrival of the first resident crew in early November.