Shuttle astronauts Jerry Ross and Lee Morin will make the fourth and final spacewalk of the STS-110 mission of Atlantis today, stepping out of the International Space Station’s Quest airlock at 9:34 a.m. Many of their tasks focus on helping future spacewalkers.

Work during the 6½-hour spacewalk includes installation a 14-foot beam extending from Quest to the newly installed S-Zero (S0) Truss to help spacewalkers maneuver around the station more efficiently. They will install halogen work lights on the Unity module and the U.S. laboratory, Destiny -- the 40-watt lamps are five times more powerful than standard 40-watt lamps and will shine a 9- by 7-foot elliptical beam of light 20 feet away. The spacewalkers will setup and partially assemble a work platform.

Ross, working from the station’s robotic arm, also will install shock absorbers to either side of the Mobile Transporter to provide a barrier and attach point between the railcar and future hand-propelled carts that will be used by spacewalkers.

Morin will deploy an instrument to measure and characterize the radiation environment outside the station. He also will troubleshoot a balky bolt on a redundant cable cutting system on the Mobile Transporter. A successful test run of that railcar concluded late Monday when ground controllers commanded it to latch onto the railway and plug into a power source. The railcar is ready to receive the Mobile Base System during the next shuttle mission, STS-111, giving the station’s Canadarm2 points of attachment on the rail-car base capable of moving along the station’s Integrated Truss.

Additional tasks include installing handrails on S0, relocating tools for STS-111 spacewalks, adjusting a thermal blanket partly obstructing a GPS antenna on S0, performing photo and video documentation of station components and checking out a gauge that is designed to detect minute amounts of gas in the environment of space.

The Atlantis crew – Commander Mike Bloomfield, Pilot Steve Frick, Mission Specialists Ellen Ochoa, Rex Walheim, Steve Smith, Morin, and Ross– was awakened at 3:44 a.m. to “I Am an American,” performed by the Purdue University Marching band. It was dedicated to Purdue graduate Ross. The station crew – Commander Yury Onufrienko, Flight Engineers Carl Walz and Dan Bursch – was also awakened at 3:44 a.m.

The next STS-110 mission status report will be issued this evening, or earlier if events warrant.

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