Space Walk
Flight Engineer Doug Wheelock is attached to Canadarm2 as he removes the failed 780-pound ammonia pump module. Tracy Caldwell Dyson assists him from the S1 Truss during Wednesday's spacewalk.

The Expedition 24 crew enjoyed a full day off Friday after the completion of a second contingency spacewalk Wednesday to replace a failed ammonia pump module. Over the weekend, Flight Engineers Doug Wheelock, an Army colonel, and Tracy Caldwell Dyson will prepare for a third spacewalk to continue the installation and activation of a spare ammonia pump module on the S1 Truss. That spacewalk is planned for Monday a little before 7 a.m. EDT. NASA managers also are considering a fourth spacewalk for cleanup activities at the worksite.

The failed pump module that provided cooling for the International Space Station's systems was removed from the S1 Truss during Wednesday's repair spacewalk. It was temporarily stowed on an external stowage platform adjacent to the Quest airlock. The first repair spacewalk took place Saturday, Aug. 7 and lasted a record 8 hours, 3 minutes.

Flight Engineer Shannon Walker has been assisting the spacewalkers from inside the station and operating Canadarm2, the station's robotic arm. Specialists on the ground carefully plotted the robotic maneuvers necessary for Walker to move the spacewalkers into their work positions. The procedures were sent up for her to practice in between spacewalks.

After the original pump module failed two weeks ago ground controllers powered down numerous station systems and readjusted them to provide maximum redundancy. Mission managers and astronauts on the ground also quickly began choreographing the contingency spacewalks and planning repair procedures. The spacewalks were planned several days apart to give crew members time to rest and managers on the ground time to review data and make necessary adjustments.

Wheelock, designated as EV1, or extravehicular crew member 1, has been wearing a spacesuit with red stripes on the legs. Caldwell Dyson, designated as EV2, has been wearing an unmarked spacesuit. Monday's spacewalk will be Wheelock's sixth and Caldwell Dyson's third.

Approximately two hours after the conclusion of Monday's spacewalk NASA TV will broadcast a briefing from Johnson Space Center. The briefing participants will include Mike Suffredini, International Space Station program manager; Courtenay McMillan, Expedition 24 spacewalk flight director; and David Beaver, Expedition 24 spacewalk officer.

In response to the power reconfiguration steps last weekend, the science team worked quickly to establish a plan to preserve experiment samples in the Japanese Experiment Module freezer. The on-orbit crew was able to transfer all the samples from the freezer in the Kibo laboratory to an operating freezer. No science samples were lost due to the pump module anomaly.

While the crew schedule has been interrupted to support the newly added spacewalks, the payload ground teams have been working closely with mission controllers to preserve and re-plan high priority activities. Other activities that can be rescheduled with little or no impact are being postponed to a later date.

Page last updated Fri July 22nd, 2011 at 12:16