10 p.m. CDT Monday, April 12, 2010
Mission Control Center, Houston, Texas
STS-131 MCC Status Report #16
HOUSTON – Spacewalkers Rick Mastracchio and Clayton Anderson will begin the third and final spacewalk of the mission, finishing the installation of a new ammonia tank for the International Space Station’s cooling systems and continuing transfers of equipment and supplies.

Mission Control played the song "Galileo" by the Indigo Girls as a wake-up for Mission Specialist Dottie Metcalf-Lindenburger and the rest of the baker’s dozen crew -- Commander Alan Poindexter, Pilot James P. Dutton Jr. and Mission Specialists Stephanie Wilson, Naoko Yamazaki, Mastracchio and Anderson -- at 9:21 p.m. CDT.

Mastracchio and Anderson spent the night in the Quest airlock, preparing their bodies for the lower pressure of the spacesuits, to protect against decompression sickness.

Robotic arm operators Wilson, Dutton and Soichi Noguchi will activate Canadarm2, the station’s arm, and grapple the old ammonia tank that was removed earlier in the mission and stored on the station’s Mobile Base System. They’ll move the depleted tank into Discovery’s payload bay so that Mastracchio and Anderson can bolt it onto a logistics carrier for the ride home to Earth.

The 6.5-hour spacewalk is scheduled to begin at 2:11 a.m. CDT Tuesday, and has been replanned because of some difficulties bolting down the new ammonia tank on Sunday. Mastracchio will wear a suit with red stripes around the legs, and Anderson will wear an unmarked suit. Metcalf-Lindenburger will coordinate the spacewalk from inside the complex.

The first task will be to connect the fluid lines to the new ammonia tank. This was not attempted during the second spacewalk because there wouldn’t have been enough time to let any ammonia that might have leaked sublimate into the vacuum of space. They’ll then move on to secure the old tank in Discovery’s cargo bay.

Additional tasks will include retrieval of micrometeoroid shields from outside the airlock and an experiment platform from the end of the Columbus laboratory. The last planned task will be to try to tighten bolts on a radiator grapple fixture beam on the port-side radiator, which couldn’t be secured earlier. If the bolts can’t be tightened, the spacewalkers will be asked to return it to the airlock for further troubleshooting.

Transfer activities will resume inside the station. With about three-quarters of the science rack, equipment, food and supply moves complete, loadmaster Yamazaki and her team will work to get all the items into their final locations.

Expedition 23 Commander Oleg Kotov and Flight Engineers T.J. Creamer and Noguchi assisted with transfers and worked with experiments. The newest members of Expedition 23, Flight Engineers Tracy Caldwell Dyson, Alexander Skvortsov and Mikhail Kornienko continued orienting themselves to their new home in space after docking just a few days before Discovery’s arrival and the start of the busy docked operations period.

The next status report will be issued after the spacewalk, or earlier if events warrant.

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