Spacewalkers get early start to station repairs

Thirty-five minutes ahead of schedule, spacewalkers Doug Wheelock and Tracy Caldwell Dyson have begun a third spacewalk to repair a failed International Space Station coolant system.

The pair of NASA astronauts, two of six residents on the outpost, switched their spacesuits to battery power at 6:20 a.m. EDT to mark the start of the 150th spacewalk supporting station assembly and maintenance.

They floated outside the Quest airlock about 10 minutes later.

The focus of today's effort is to install a spare pump module on the starboard side of the station, replacing a failed one the astronauts removed last Wednesday.

The spare is on a platform attached to the Quest airlock. It was delivered to the station in 2006 and is one of four available in orbit.

The spacewalkers will attempt to install the bulky, 780-pound device on the Starboard 1 truss segment.

The spacewalk is expected to last about six-and-a-half hours.

You can watch the action live here by clicking on the NASA TV box at right to launch a viewer.

Wheelock can be identified by a suit with red stripes on the legs and No. 19 in faint white writing in the lower right corner of his helmet camera view. In communications with the ground, he may be called "EV-1" or by his nickname "Wheels."

Caldwell Dyson's suit has no stripes; her helmet camera shows No. 20. She'll be called "EV-2" or "TC," her first two initials.

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