WASHINGTON, May 20 (Xinhua) -- Two U.S. astronauts conducted the first of four spacewalks for space shuttle Endeavour's STS-134 mission on Friday morning, the U.S. National Aeronautics and Space Administration (NASA) said.

According to the U.S. space agency, Endeavour's mission specialists Andrew Feustel and Greg Chamitoff completed the six-hour, 19-minute spacewalk at 9:29 a.m. EDT (1329 GMT). They successfully installed antennas for the External Wireless Communication system, routing cables, setting up the antenna, installing handrails, and connecting power cables.

Because of a carbon dioxide sensor failure in Chamitoff's spacesuit, flight controllers limited his spacewalk time to about six hours 20 minutes, 10 minutes less than the planned six hours and 30 minutes. There was no indication his suit's carbon dioxide levels would rise. However, they deferred tasks to remove a micrometeoroid debris shield to access and attach some of the connection points.

This was the 245th spacewalk conducted by U.S. astronauts. It was Feustel's fourth spacewalk for a total time of 27 hours and 17 minutes, and Chamitoff's first.

Endeavour lifted off on Monday morning from Kennedy Space Center in Florida, to deliver to the International Space Station a 2-billion-dollar, multinational particle detector known as the Alpha Magnetic Spectrometer (AMS).

AMS, a particle physics detector, is designed to search for various types of unusual matter by measuring cosmic rays. Its experiments are designed to help researchers study the formation of the universe and search for evidence of dark matter, strange matter and antimatter.