Live in orbit: Final spacewalk off to early start

Blogger update, 8:21 a.m.: Marshburn quickly finished his work with Dextre and is moving on to the Kibo lab's porch to install video cameras. Cassidy is expected to join him soon.

Endeavour spacewalkers Tom Marshburn and Chris Cassidy are off to an early start to the mission's fifth and final spacewalk outside the International Space Station.

The pair switched their spacesuits to battery power at 7:33 a.m. EDT, almost an hour ahead of their scheduled 8:28 a.m. start, as the station flew 215 miles above the Atlantic Ocean.

The spacewalk is expected to last about 6.5 hours.

After about 45 minutes of prep work, the spacewalkers will split up to tackle separate tasks, the first in a series of jobs planned today.

Marshburn, a 48-year-old former emergency physician and flight surgeon from North Carolina, will tighten some loose insulation on the two-armed, Canadian-built robot called Dextre, or the Special Purpose Dexterous Manipulator. It's attached to the U.S Destiny module.

Cassidy, a 39-year-old NAVY SEAL from Maine, will work at the center of the station's central truss, at the segment called Z1. He'll rewire some cables so that two gyroscopes that help control the station's orientation each have their own power supply.

If you're watching NASA TV - click on the still image on the right side of this page to launch a viewer - you can identify the spacewalkers by the markings on their suits and the numbers of their helmet cameras.

Marshburn, who is today's lead spacewalker, has dashed red stripes on his suit and No. 16 in the bottom right of his helmet camera.

Cassidy's suit has barber pole stripes, and his camera is No. 18.

Endeavour mission specialist Dave Wolf is guiding the two spacewalkers from inside.

This is the 130th spacewalk supporting maintenance and assembly of the space station, which began in 1998.

It is the third career spacewalk for both Marshburn and Cassidy, who are on their first trip into space.

Along with Wolf and Tim Kopra, Endeavour's mission has totaled 25 hours and 36 minutes of spacewalking time during the first four excursions.

Click on this NASA TV schedule to see upcoming mission highlights.

And check out this Flight Day 13 Execute Package for more detailed crew timelines and notes sent by NASA's Mission Control Center in Houston.

For more information about the mission, browse through this mission summary or the full press kit.

IMAGE: In June 2008, Dextre was moved atop the Destiny Laboratory Module of the International Space Station. Dextre, built by the Canadian Space Agency, has arms more than 9 feet in length and can attach power tools as fingers. Behind Dextre is the blackness of space, while Earth looms over Dextre's head. Credit: NASA.