Pilot Rick Sturckow and Mission Specialist Nancy Currie will continue their work removing access panels inside Unity and unstowing hardware that will be used by visiting astronauts on future assembly missions.
Commander Bob Cabana, Sturckow and Currie will work inside Unity to locate part of a missing mid-bay rack pivot fitting, which was lost yesterday. Following removal of launch restraint bolts, the lock ring fell behind the panel during attempts to install it on the rack. The pivot fitting will allow the entire equipment rack to be tilted forward.
After turning off the lights and ventilation system, Endeavour's crew will close the hatch and leave Zarya for the final time just before 4 p.m. Central time. Prior to closing the hatch, Endeavour's life support systems will be used to increase the station and Shuttle atmospheric pressure to 15 pounds per square inch, a little above sea level pressure on Earth. Then, as each hatch is closed in the station, the crew will lower the pressure slightly to keep positive air pressure on the inside of each hatch to assist in sealing the hatches. Dessicant bags will be installed in Unity's portable, battery-operated fans to remove humidity from the module and the portable fans will be left running. The crew's final exit from Unity is set for just after 5:30 p.m. today.
After they have completed exiting the station, Cabana and Sturckow will lower the pressure inside Endeavour from 14.7 pounds per square inch to 10.2 pounds per square inch in anticipation of tomorrow's spacewalk. The lower air pressure will reduce the amount of time Newman and Ross must spend breathing pure oxygen before beginning their spacewalk on Saturday and going to the lower pressure of their spacesuits, 4.3 pounds per square inch of pure oxygen.
The oxygen pre-breathe protocol removes nitrogen from the bloodstream to prevent a potentially dangerous malady commonly referred to as the "bends," caused when nitrogen bubbles form in the bloodstream. Newman and Ross also will pre-breathe pure oxygen from masks for about an hour today during the depressurization of Endeavour as part of the protocol.
Later, Newman will complete a performance evaluation of the Orbiter Space Vision System targets, part of an alignment aid for operations with the Shuttle's mechanical arm. Endeavour's crew will be interviewed by CNN and CBS News at 7:36 p.m. Central time.
Preparations will get under way late this evening for tomorrow's third and final spacewalk by Newman and Ross. With Sturckow's assistance, they will prepare the tools they will use, then check out the Simplified Aid for Extravehicular Activity Rescue (SAFER) backpacks, which are a type of space "life jacket" that provides the capability for spacewalking astronauts to fly back to the station should they become untethered. During tomorrow's spacewalk, Ross will check out a new valve on the unit, firing the backpack's jets while remaining tethered to Endeavour.
Endeavour and the International Space Station remain in excellent shape.