Successfully completing a major objective, astronauts Douglas Wheelock and Tracy Caldwell Dyson unbolted and removed a faulty 780-pound ammonia coolant pump from the space station's starboard one, or S1, truss segment today after disconnecting a final ammonia line and five electrical cables.

The astronauts had problems lining up and attaching a handling fixture to the pump, but they finally got it lined up and secured. That cleared the way for robot arm operator Shannon Walker, working inside the Destiny lab module, to pull Wheelock, holding the pump by the grapple bar, away from the S1 truss at 1:30 p.m.

"How you doing, Wheels?" Caldwell Dyson called as Wheelock pulled the pump module from the truss.

"Doing good," he replied. "Trying to be still with this thing."

Walker then carefully repositioned the arm and Wheelock mounted the pump module on a powered payload attachment fixture at the base of the station's robot arm transporter at 1:55 p.m.

Caldwell Dyson, meanwhile, was cleared to make her way to external storage platform No. 2 where she planned to loosen three of four bolts holding a spare pump module in place.

The spare pump will be installed on the S1 truss during a spacewalk Sunday. Assuming the astronauts don't run into problems re-attaching five electrical cables and four ammonia lines, flight controllers will be able to re-activate the loop A coolant system, completing a complex repair job.