Down to the Wire for Station Repair Spacewalks, CBS

"NASA astronauts and engineers are refining plans for two spacewalks by astronauts Douglas Wheelock and Tracy Caldwell Dyson to replace a large ammonia pump module that shut down Saturday, knocking out one of the International Space Station's two cooling loops. The astronauts hope to carry out the first spacewalk Friday morning, starting at 6:55 a.m. EDT, and a second excursion Monday to finish the job, one of the so-called "big 14" on a list of critical components that require spacewalk repair if problems crop up. NASA managers initially targeted Thursday for the first spacewalk and Sunday for the second, but decided late Monday they needed more time to review procedures. "This is an anomaly we knew someday would happen," said space station Program Manager Mike Suffredini. "It's an anomaly we have trained for; it's an anomaly we have planned for." With four spare pump modules on board the station, "we're in a good position to go solve this problem," he said. "It is a significant failure, though, in terms of systems on board ISS, so it's one we need to go after."