Two astronauts conducted a five-hour spacewalk today, finishing up the last priorities of Endeavour's mission, while their crewmates inside prepared for an early undocking, now scheduled for Sunday.

Mission Specialist Dave Williams and International Space Station Flight Engineer Clay Anderson left the station's airlock at 8:17 a.m. By the time they returned at 1:19 p.m., they'd completed all of the tasks scheduled for the replanned spacewalk, which was trimmed by two hours to allow for a day-early hatch closing at 4:10 p.m. CDT today.

Williams and Anderson installed the External Wireless Instrumentation System antenna, attached a stand for the shuttle's robotic arm extension boom and retrieved the two materials experiment containers to be brought home on the shuttle. Two other tasks originally planned for the spacewalk - cleaning up and securing debris shielding and moving a tool box to a more central location - were deferred to a future spacewalk.

DOUBLE SPACESHIP FLYBYS: Space shuttle Endeavour is scheduled to undock from the International Space Station on Monday, August 20th. If that happens as planned, sky watchers across North America may be able to witness something rare and beautiful: a double-spaceship transit across the night sky. US cities favored for flybys on Aug. 20th or 21st include Atlanta, Boston, Chicago, Denver, Detroit, Las Vegas, New York and Phoenix. The space station and shuttle will appear as separate, bright points of light moving in tandem. Flyby times depend on where you live. Subscribers to Spaceweather PHONE ( http://spaceweatherphone.com ) will receive phone and email alerts when the pair are about to appear. Flyby timetables are also available from Heavens Above ( http://heavens-above.com ).