HOUSTON, Dec. 22 (Xinhua) -- The first astronaut to float untethered in space died Thursday in the U.S. state of California at the age of 80, confirmed officials of the U.S. National Aeronautics and Space Administration (NASA).

Bruce McCandless II, originally from Boston, Massachusetts, was one of the 19 astronauts selected in April 1966. He flew on two space shuttle missions respectively in 1984 and 1990.

During his 1984 mission, McCandless became the first astronaut to fly untethered from the spacecraft using the Manned Maneuvering Unit (MMU). The photograph taken of that spacewalk now is considered one of NASA's iconic photos.

"He will always be known for his iconic photo flying the MMU," said Robert Lightfoot, NASA's acting administrator.

McCandless' 1990 mission entailed the deployment of the Hubble Space Telescope, which has been used to observe the most distant stars and galaxies as well as the planets in the solar system.

McCandless, a retired U.S. Navy captain, logged more than 312 hours in space. He also contributed to NASA missions when he was not in space. He was the mission-control communicator for the Apollo 11 Moonwalk mission, completed by and Buzz Aldrin. He was also the backup pilot for the first Skylab mission.