Astronauts to Take Fifth Spacewalk at Space Station
Astronauts Tom Marshburn (left) and Christopher Cassidy share duties on the fourth spacewalk on July 24, 2009 during Endeavour's STS-127 mission and its crew's joint activities with the space station.
Credit: NASA

Two astronauts will venture outside the International Space Station Monday to tackle some final tasks in the fifth and last spacewalk of their mission to the orbiting laboratory.

Astronauts Chris Cassidy and Tom Marshburn are slated to don bulky NASA-issue spacesuits and begin the planned 6 1/2-hour service call at about 8:28 a.m. EDT (1228 GMT), but could start earlier if they run ahead of schedule. They plan to tackle some last remaining maintenance chores during the excursion.

The two astronauts will use a different type of air-scrubbing canister in their spacesuits than the ones used on their last two spacewalks. During those spacewalks, Cassidy?s quick, strenuous pace outmatched his air scrubber?s ability to keep his carbon dioxide levels down.

While Cassidy, a veteran Navy SEAL who was deployed to Afghanistan in 2001 just after the 9/11 terrorist attacks, was never in any danger during those spacewalks, he has received some good-natured ribbing from the 12 other astronauts with him aboard the linked station and shuttle Endeavour.

?Yes, I am taking quite a bit of teasing about this,? Cassidy said during a televised briefing with reporters Sunday. ?I have a whole lot of confidence in the suit.?

During today?s spacewalk, Cassidy and Marshburn plan to rewire power cables for the station?s American-built attitude control system, fix loose insulation on Dextre - a Canadian maintenance robot - and install a pair of television cameras on the outpost?s Japanese Kibo laboratory. They also hope to set up a spare parts storage mechanism need for a future shuttle flight.

Cassidy and Marshburn will both make their third career spacewalk during the orbital work, which will wrap up a five-spacewalk marathon by the space shuttle Endeavour?s crew to upgrade the station, deliver spare parts and install a Japanese experiment porch at the end of the $1 billion Kibo laboratory.

Endeavour commander Mark Polansky said that he has total confidence in his spacewalking crew and the support from Mission Control, though his crew will be as vigilant as ever during today?s spacewalk.

"I think we're all keenly aware that [spacewalks] carry some risk to them and so we're going to be very, very deliberate and careful about the last [spacewalk],? Polansky said Sunday. ?Because in my book, the last one you do is always the one you have to watch out for the most.?

Polansky and his crew are in the homestretch of a 16-day mission to the International Space Station. Endeavour is slated to leave the space station Tuesday and land in Florida on Friday.

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  • Video - The Kibo Lab: Japan's Hope in Space - Part 1, Part 2
  • Video Show - The ISS: Foothold on Forever is providing continuous coverage of STS-127 with reporter Clara Moskowitz and senior editor Tariq Malik in New York. Click here for mission updates and's live NASA TV video feed.