Friday, July 24, 2009

Live in orbit: fourth spacewalk under way

Endeavour mission specialists Chris Cassidy and Tom Marshburn have switched their spacesuits to battery power, officially beginning today's spacewalk.

It's the fourth of five planned during Endeavour's stay at the station, and is expected to be a long one: seven hours, 30 minutes.

The spacewalk officially started at 9:54 a.m. EDT. as the station flew 222 miles above Kazakhstan, a couple of minutes after the Quest airlock's hatch was opened.

Speaking of Kazakhstan, an unmanned station resupply ship launched from there today at 6:56 a.m. EDT.

The Progress 34 spacecraft blasted off from the Baikonur Cosmodrome carrying 2.5 tons of supplies. It is scheduled to dock at the station at 7:16 a.m. Wednesday, the day after Endeavour departs.

Cassidy and Marshburn are expected to take about 35 minutes to climb out to the far left end station's central truss, a distance of more than 50 yards.

At the Port 6 truss, they prepare to swap out four nickel-hydrogen batteries that store power from the set of solar array wings on the truss - the first delivered to the station, in 2000.

During the spacewalk, Cassidy, the lead spacewalker, can be identified by the spacesuit with barber pole red and white stripes. His helmet camera shows No. 18 in the bottom right corner of the screen.

Marshburn's suit has dashed red and white stripes. His helmet camera shows No. 16 in the bottom right corner.

The spacewalk is the 129th supporting assembly and maintenance of the station. Total spacewalking time before today was 798 hours and 30 minutes.

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