Installation of a 1,700-pound ammonia tank on the International Space Station

8:15 a.m. CDT Sunday, April 11, 2010

Mission Control Center, Houston, Texas

STS-131 MCC Status Report #13

HOUSTON - Discovery Mission Specialists Rick Mastracchio and Clayton Anderson installed a 1,700-pound ammonia tank on the International Space Station, completing the second of a three-spacewalk coolant tank replacement process.

The 7-hour, 26-minute spacewalk, began at 12:30 a.m. CDT, about 45 minutes ahead of schedule. The first task was to unhook and remove the depleted ammonia tank from the station’s starboard truss.

Mission Specialist Stephanie Wilson and Pilot James P. Dutton Jr. used the station’s Canadarm2 to move the empty tank to one of the mobile equipment carts on the tracks of the truss. There the spacewalkers temporarily stowed it until the third spacewalk Tuesday when it will be moved to Discovery’s payload bay for return home. The spent tank will be refurbished for delivery back to the station as a spare on the STS-134 mission.

The arm next retrieved the new tank from its temporary parking spot on the Quest airlock where it had been left during the first spacewalk Friday. After a bit of trouble with one of the four bolts, the new tank was secured in place and the electrical connections were mated. Because of the balky bolt delay, connection of the tank’s fluid lines was postponed until the Tuesday spacewalk.

With help from Mission Specialist Dorothy Metcalf-Lindenburger, the in-cabin choreographer, Mastracchio and Anderson also installed two radiator grapple fixture stowage beams on the P1 Truss. Scheduled retrieval of debris shields also was postponed.

The stowage beams will stow handles that could be used if replacement of a radiator became necessary.

Today’s was the 142nd spacewalk for station construction and maintenance. It was the fifth for each astronaut bringing Mastracchio’s total spacewalking time to 32 hours, 6 minutes and Anderson’s to 32 hours and 4 minutes.

Tuesday’s spacewalk, also by Mastracchio and Anderson, is the last planned for Discovery’s mission to the station. It is to begin at 2:11 a.m. and last about 6½ hours. In addition to relocating the old tank to Discovery’s payload bay for return home, the final spacewalk includes retrieval of a light-weight adapter plate assembly from the Columbus module and securing it in the cargo bay, replacing a camera light on the Destiny laboratory, installing two more radiator grapple fixture stowage beams and installing a camera on Dextre, the Special Purpose Dexterous Manipulator.

The next status report will be issued after crew wakeup tonight at 8:51 p.m.