Today's 6-1/2-hour space walk by Newman and Mission Specialist Jerry Ross is scheduled to begin about 3 p.m. Central time, but may start earlier if the astronauts are ready to depressurize Endeavour's airlock ahead of schedule. Ross and Newman will install two box-like antennas on the outside of the Unity module that are part of the S-band early communications system. The antennas will allow U.S. flight controllers to monitor Unity's systems. Additional S-band electronics gear will be set up inside Unity on Thursday after astronauts enter the module for the first time. The spacewalkers also will connect an external video cable between Zarya and the S-band system. This cable will support early communications videoconferencing from Zarya. The system's videoconferencing capability will be tested after Thursday's installation. Newman, positioned on the end of Endeavour's robot arm, then will install a sunshade over one of Unity's externally mounted computers.
Ross and Newman will remove launch restraints over four hatchways on the Unity module to which future station modules, an early exterior framework and a cupola will attach. The hatchways, or Common Berthing Mechanisms, serve as docking ports for new hardware that will be delivered to the station during the next 18 months. Then Newman will install insulating covers on the trunnion pins that held Unity in the Shuttle's cargo bay.
If time allows toward the end of today's spacewalk, and pending final approval from U.S. and Russian managers, Ross and Newman may try to free one of two balky antennas on the TORU system, Zarya's backup rendezvous navigation system. Still attached to the robot arm, Newman would use an extendable, 10-foot-long grappling hook in an attempt to unfurl the antenna. Flight controllers believe that stiff cabling or interference from thermal blankets on Zarya may be preventing the antennas from fully extending, even though pyrotechnic pins have fired to enable the antennas to roll free from their spools. If Newman is successful, the same procedure may be used to free the second antenna on Saturday during the third and final spacewalk.
The last task for today will be to disconnect and stow cables that were used by Endeavour's crew to control the docking mechanism, called the Androgynous Peripheral Attach System (APAS), that docked Zarya to Unity earlier in the mission. With that system never again to be opened, the cable used by Endeavour to control it, which runs along Pressurized Mating Adapter 2 (PMA 2), will be disconnected on this spacewalk as a "get-ahead task" for future assembly missions when PMA 2, currently the adapter to which Endeavour is docked, will be moved. Ross and Newman also will spend some time bundling umbilicals on the exterior of Zarya and ensuring that the markings used by the Space Vision System robotic arm alignment aid are not obstructed by any cables.
After the spacewalk is complete, Currie will use Endeavour's robot arm to survey the payload bay and videotape all of the Space Vision System targets on Unity and Zarya.
Systems on board Endeavour and the International Space Station continue to operate smoothly.