This afternoon's spacewalk, set to begin about 3:06 p.m. CST, could get under way earlier if Mission Specialists Jerry Ross and Jim Newman are ahead of schedule in their space walk preparations. Today's activities will be devoted mostly to tasks that ready the station for future assembly work.
The crew's first job will be to release some cable ties on four cables connected on an earlier space walk, three located on Unity's upper mating adapter and one on its lower adapter, to relieve tension on the lines. Flight controllers noted the cable tension from camera views of the station, and they are concerned that leaving the cables as they are would not allow enough play in them to accommodate cyclical heating and cooling that occurs between orbital night and day. The space walkers also will check an insulation cover on one cable connection on the lower Pressurized Mating Adapter (PMA 2) to make sure it is fully installed.
Ross and Newman then will attach a bag of tools - wrenches, power grip tools, ratchets and foot restraints - on the side of Unity's upper mating adapter (PMA 1). Astronauts Tammy Jernigan and Dan Barry will use these tools during their space walk next May during the STS-96 assembly mission. Ross and Newman also will inspect bubbling paint that has been noted on some of the Orbiter Space Vision System targets on Unity.
Next, the space walkers will disconnect cables that the crew used to operate the docking mechanism on Unity's upper mating adapter when Zarya was docked earlier in the mission. Also, Ross will use a 10-foot-long grappling hook to try to free the second of two jammed antennas that are part of Zarya's backup rendezvous navigation system. The first antenna was successfully deployed on a space walk Wednesday by Newman using the same method. After the antenna deploy, Ross will stow the grappling hook on the outside of Zarya, and he and Newman will install a handrail at the far end of the module.
Near the end of the space walk, after packing up their tools , the astronauts will do a detailed photographic survey of the space station from top to bottom. Finally, each astronaut will test fire the Simplified Aid for Extravehicular Activity Rescue (SAFER) jet backpacks they are wearing, a type of space "lifejacket," that would allow an astronaut to fly back to the station if they should ever become untethered. During an earlier flight test on STS-86, a valve failed and prevented the propulsion jets on the backpack from firing. The valve was redesigned and extensively tested on the ground and today's in-flight test will assist in verifying the new design.
With the first steps in the orbital construction of the International Space Station completed, Endeavour is planned to undock from the new outpost at 2:25 p.m. CST on Sunday, leaving the 7-story, 35-ton complex to fly on its own for the next five months. Station flight controllers will be able to monitor the health of the station through an S-band communications system installed in Unity by the astronauts.
Endeavour and the International Space Station are orbiting the Earth at an altitude of 246 statute miles with all systems operating normally.