Endeavour astronauts take a walk outside space station

Drew Feustel along the port side of space station at 5:48 a.m. (NASA)

Two of shuttle Endeavour's astronauts went outside the International Space Station to perform a few chores on the first of four spacewalks planned during the shuttle's twelve day visit.

Spacewalkers Drew Feustel and Greg Chamitoff began the first spacewalk of the mission at 3:10 a.m. EDT, and then left the Quest airlock to translate over to the right section of the space station's truss.

The first order of business was for the duo to head over to the Starboard Truss to retrieve the Materials International Space Station Experiment or MISSE 7A and 7B, for their return to earth.

Delivered to the space station and placed on the Express Logistics Carrier 2 in November 2009 during STS-129, the astronauts began by removing the lone power cable attached to each experiment and closed it up. The pair then removed the two pins which held each experiment in place and then stored them in the shuttle's payload bay for the return back to earth.

Feustel then retrieved MISSE 8 from Endeavour's bay and carried it over to the express carrier and installed where 7A had been located.

Chamitoff then moved over to the Starboard 3 segment of the Truss, or backbone of the space station, to begin installing a light on Crew Equipment and Translation Aid cart.

Today's spacewalk is the fourth by Feustel and the first by Chamitoff, and it can be very exhausting to an astronaut during his first venture outside the spacecraft.

Several space station astronauts have depleted their oxygen early by either working to fast or breathing to much as they strain to become accustomed to their new environment.

Feustel, who performed three spacewalks two years ago during the final Hubble Space Telescope servicing flight, was able to control his oxygen intake through his suit. Meanwhile, first timer Chamitoff made a couple of returns back to the airlock to recharge his oxygen in the first three hours of the spacewalk.

Over four hours into the spacewalk, Chamitoff's carbon dioxide sensor in his spacesuit failed with Mission Control unable to receive data on the ground.

The failure forced the orbital duo to stop work outside the station so that Mission Control could access how much time would be needed to complete the tasks safely.

After much discussion, the control center informed the astronauts to begin wrapping up work and focus on the clean up of two work sites and prepare to return to the airlock early.

Feustel and Chamitoff began entering the Quest airlock at 9:13 a.m., a half-hour earlier than planned.

Several unplanned work details were performed, however most of the orbital walk in space ran 15 minutes behind schedule.

"I want to thank both of you on an outstanding EVA (extravehicular activity)," spacewalking coordinator Fincke radioed the pair upon entering the airlock. Fincke also congratulated Chamitoff on his first spacewalk and sent wishes to controllers on the ground.

Today's first spacewalk lasted a total six hours and 19 minutes, and was the 115th from the space station's airlock.

Today's 'walk was the 156th spacewalk in support of building and maintenance of earth's orbiting outpost in space, during a combined 980 hours and 12 minutes.

The second space walk by astronauts Feustel and Mike Fincke is planned for Sunday morning at 2:16 a.m.