Washington -- U.S. astronauts completed a spacewalk to attach a replacement coolant tank to the International Space Station, NASA officials said.
Mission Specialists Rick Mastracchio and Clayton Anderson installed an ammonia tank weighing 1,700 pounds during a 7 1/2-hour spacewalk Sunday, NASA reported.
The tank was mounted during the second of three spacewalks scheduled for shuttle Discovery's mission to the International Space Station, NASA said.
Temporary problems with attaching bolts made the spacewalk longer than intended, leaving several additional tasks, including connecting the tank's fluid lines, uncompleted.
Those operations will be deferred to a final spacewalk on Tuesday.