HOUSTON - On Wednesday, the Expedition 15 crew completed the second spacewalk in eight days and continued preparations for space shuttle Atlantis' arrival at the International Space Station.

Commander Fyodor Yurchikhin and Flight Engineer Oleg Kotov opened the hatch on the Pirs docking compartment at 10:23 a.m. EDT to begin a spacewalk lasting 5 hours and 37 minutes. The cosmonauts installed sample containers on the Pirs module for a Russian experiment. The experiment, called Biorisk, looks at the effect of space on microorganisms.

Next, the spacewalkers strung a section of Ethernet cable on the exterior of the Zarya module. This completed the installation of a remote computer network that will enable commanding of the station's Russian segment from the U.S. segment, if necessary.

Yurchikhin and Kotov later moved to the primary task on the agenda, putting up 12 debris shield panels on the conical section of the Zvezda module. Five panels were installed last week, and six others were installed in 2002 to improve the module's protection from micrometeroid debris strikes. The aluminum panels each measure approximately 2 feet by 3 feet and are 1 inch thick.

Almost two and a half hours into the spacewalk, Russian controllers noticed unusual readings in Pirs and asked Yurchikhin to return to the module where he verified that the pressurized oxygen bottles were closed properly. Mission Control Moscow subsequently determined that a small amount of oxygen was flowing from a fluid umbilical that had not closed fully when it was disconnected from the spacesuit at the beginning of the spacewalk. Controllers closed the flow of oxygen to that umbilical to preserve the supply and restarted it during repressurization of Pirs after the spacewalk concluded.

The spacewalk ended at 4:00 p.m. when the hatch on Pirs was closed. Both cosmonauts now have 11 hours and 2 minutes experience in the Russian Orlan spacesuits. This was the 83rd spacewalk in support of station assembly and maintenance, the 55th conducted from the station, and the 22nd conducted out of Pirs.

During Wednesday's spacewalk, Flight Engineer Suni Williams remained aboard the station monitoring the spacewalk, exercising and conducting experiment activities. Earlier this week, she and her crewmates prepared the Quest airlock for the spacewalks planned during Atlantis' mission. They also packed her personal items and experiment results for her return to Earth aboard Atlantis. Early in the morning of June 16, Williams will exceed astronaut Shannon Lucid's mark for the longest spaceflight ever by a woman, 188 days and 4 hours.

Commander Rick Sturckow and the crew of shuttle Atlantis are in Florida preparing for their scheduled launch Friday, June 8, at 7:38 p.m. EDT. STS-117, due to dock to the station at 3:49 p.m. EDT Sunday, June 10, delivers a new set of solar array wings and a new station flight engineer, NASA astronaut Clay Anderson.