Two U.S. astronauts conducted the third of four scheduled spacewalks for space shuttle Endeavour 's STS-134 mission on Wednesday morning, the U.S. National Aeronautics and Space Administration (NASA) announced.
Endeavour's mission specialists Drew Feustel and Mike Fincke completed a six-hour-54-minute spacewalk at 8:37 a.m. EDT (1437 GMT). They completed all planned tasks, installing cables to increase redundancy for the power system on the Russian segment of the station, completing the external wireless antenna system work Feustel and Greg Chamitoff began during the first spacewalk, and installing a power and data grapple fixture to Zarya. The fixture will allow the station's robotic arm to "walk" to the Russian segment, extending its reach by using that grapple fixture as a base.
It was the 247th spacewalk conducted by U.S. astronauts, and the 158th in support of space station assembly and maintenance, totaling 995 hours and 13 minutes. If everything goes as planned, the 1,000th hour of space station assembly and maintenance will be logged on Friday.
Endeavour lifted off on May 16 from the 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.
NASA's 30-year-old shuttle program is ending due to high operating costs. The Obama administration wants to spur private companies to get into the space taxi business, freeing NASA to focus on deep space exploration and new technology development.
There were initially five space shuttles in the fleet -- Challenger exploded shortly after liftoff in 1986 and Columbia disintegrated on its way back to Earth in 2003. Discovery retired earlier this year, while Endeavour is currently on its final mission. A last mission for Atlantis is scheduled for July, though funding for Atlantis remains in question.
The sixth shuttle, Enterprise, did test flights in the atmosphere but was never flown into space. It is already on display at a museum outside Washington.
When the U.S. space shuttle program officially ends later this year, the Russian space program's Soyuz capsule will be the only method for transporting astronauts to and from the station.