NASA Finds Glitch in CO2 Sensor, Cuts Short Spacewalk

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NASA cut short the first spacewalk by shuttle Endeavour astronauts -- but only by about 10 minutes -- after the space agency discovered a faulty carbon dioxide sensor in one of the adventurer's spacesuits.

The astronauts were nearly five hours into a routine six-and-a-half hour spacewalk at the International Space Station when mission controllers noticed that Gregory Chamitoff's spacesuit sensor wasn't working. NASA needs to know if levels of carbon dioxide -- expelled when you breathe -- get too high to ensure the astronauts safety.

The levels probably weren't too high, but the decision was made because of the lack of information. Chamitoff and spacewalking partner Drew Feustel still managed to finish up the tasks NASA had set before them, including the installation of an ammonia jumper cable and antennas for the External Wireless Communication (EWC) system.

Indeed, the spacewalk consisted largely of puttering around with routine chores -- installing a light fixture here, covering something there, prepping tools and picking some stuff up. The only thing unique was the location: outside the International Space Station.

The two Endeavour astronauts started their six-and-a-half hour spacewalk at 3:10 a.m. EDT Friday. NASA officials called this spacewalk "as routine as they get" for what is always a risky task: strolling outside in space.

Unlike other spacewalks, when the tasks were so tough their labored breathing could be heard on the radio, Chamitoff and Feustel didn't sound like they were out of breath.

This is the first spacewalk for Chamitoff. He called it "a dream come true for me."

Endeavour's astronauts will spacewalk four times during the last flight of space shuttle Endeavour.

Endeavour's day started with a wake-up song written by two Kennedy Space Center employees, Dan Keenan and Kenny McLaughlin. The song is called "We All Do What We Can Do" and honors workers who prepare the shuttles for launch.

On Thursday, the shuttle's astronauts accomplished their main job: installing on the station a $2 billion physics experiment that looks for antimatter and dark matter. On Saturday, the two crews will get an unprecedented VIP call -- Pope Benedict XVI will make the first papal call to space. Two Italians are on board.

After a planned 16-day mission, Endeavour is scheduled to land June 1. NASA is shutting down its shuttle program this summer after 30 years, to focus on interplanetary travel. One more mission remains, by shuttle Atlantis in July, to carry up one last load of supplies and equipment.

The Associated Press contributed to this report.