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*Astronauts Continue Spacewalk, Hatch Closure Preps*

Astronaut Dave Williams begins spacewalkImage above: Mission Specialist Dave Williams emerges from the hatch at the beginning of STS-118's fourth spacewalk. Image: NASA TV TO VIEW IMAGE GO TO:http://www.nasa.gov/mission_pages/shuttle/main/index.html

Spacewalkers continue working on the exterior of the International Space Station as their crew mates are preparing for hatch closure. Mission Specialist Dave Williams and Flight Engineer Clay Anderson began the spacewalk at 9:17 a.m. EDT(1317 UTC) and are scheduled to wrap up about 1:47 pm. (1747 UTC)

Williams and Anderson installed a stand for the shuttle’s robotic arm extension boom on the station’s truss structure. Other scheduled tasks for the shortened spacewalk include the installation an External Wireless Instrumentation System antenna and retrieval of two containers of the Materials ISS Experiment. Mission Specialist Tracy Caldwell is the spacewalk coordinator, a role that she has for all four STS-118 spacewalks.

Inside the station, astronauts and cosmonauts are preparing for hatch closure between Space Shuttle Endeavour and the station, scheduled for about 5 p.m. today.

Overnight, mission managers decided to shorten the originally planned 6.5-hour spacewalk to 4.5 hours so that the crew can close hatches between the station and shuttle at the end of the day today. That plan preserves the option to have Endeavour undock from the station on Sunday and prepare for a landing on Tuesday. The earlier landing is being considered in the event Hurricane Dean threatens the Houston area. It could allow an opportunity for the shuttle to land before Mission Control, Houston, would be shut down in preparation for a storm.

However, managers will review the forecast for Dean and mission activities this afternoon during their daily meeting and assess whether they will continue to pursue a possible early undocking and landing.