Today's space walk, scheduled to begin about 4:30 p.m. Central time, may begin earlier if Ross and Newman are ready to depressurize Endeavour's external airlock ahead of schedule. This space walk, which will last 6-1/2 hours, will focus on connecting computer and electrical cables between Unity, the two mating adapters attached to either end of Unity, and Zarya. In all, Ross and Newman will make about 40 connections during the spacewalk. This will enable power to flow to Unity for the first time in orbit and will permit Unity's avionics, computers and heaters to be activated.
Ross and Newman will begin today's space walk by readying Endeavour's payload bay for their activities. Then, as Ross rides on the shuttle's robot arm, he will install mating plugs and jumper cables to reroute power through Unity while Newman releases cables from where they were secured for launch on the mating adapter between Unity and Endeavour, called Pressurized Mating Adapter 2 (PMA 2). Ross and Newman will begin "plugging in" the cables and locking them into place, and then pull a thermal cover over each connector. The space walkers will next install a safety slidewire that will hold their tethers as they connect cables between the modules.
They will repeat the cable connection process again as they make connections between Unity, Zarya and the mating adapter that attaches Unity to Zarya, labeled Pressurized Mating Adapter 1 (PMA 1). Finally, they will remove thermal covers from Unity's two exterior computers, known as multiplexer-demultiplexers (MDMs), which are mounted on PMA 1.
Once the cables are connected, Russian ground controllers will send commands to Zarya to begin providing power to Unity, powering up Unity's exterior computers. At that point, Commander Bob Cabana and Mission Specialist Sergei Krikalev will send commands to the exterior computers to prepare them to accept ground commands that will activate systems aboard Unity.
Before reentering Endeavour's airlock at the conclusion of the space walk, Ross and Newman may, if time allows, perform a close-up inspection of the Telerobotically Operated Rendezvous System (TORU) on the Zarya module. Although flight controllers are confident the pyrotechnic pins holding the TORU antennas did deploy as expected, the two antennas did not unfurl as planned following Zarya's launch on Nov. 20. The antennas are part of a backup rendezvous system and are emitting signal strength in their current position and pose no problem for future station operations. At this point, there are no plans for Ross and Newman to attempt to manually deploy the antennas on a future space walk.
Early this morning, Russian and American flight controllers decided to have Krikalev replace a battery current converter unit in Zarya suspected of not working properly. A spare unit is carried aboard Endeavour. Krikalev has performed a similar activity in the past during stays on the Mir space station and will perform the task during the time the crew is inside Zarya on Thursday.
Endeavour and the International Space Station are orbiting the Earth at an altitude of about 240 statute miles with all systems in excellent shape.