The U.S. space agency paused to remember the deadly explosion of the space shuttle Challenger 25 years ago on Friday.

The shuttle broke up just after launch on January 28, 1986, killing all seven astronauts on board. The disaster was watched on live television by many Americans, including schoolchildren turned in to see the first teacher-astronaut travel into space.

A memorial service was planned at the Kennedy Space Centre in Florida.

NASA Administrator Charlie Bolden marked an annual Day of Remembrance for astronauts killed in service on Thursday by placing wreath at Arlington National Cemetery outside Washington.

The day is also used to honour three astronauts killed in a fire aboard Apollo I on January 27, 1967 and the seven crew members killed when the shuttle Columbia disintegrated on re-entry into Earth’s atmosphere on February 1, 2003.

“Throughout history, however, we have seen that achieving great things sometimes comes at great cost and we mourn the brave astronauts who made the ultimate sacrifice in support of NASA missions throughout the agency’s storied history,” President Barack Obama said in a statement.

“Through triumph and tragedy, each of us has benefited from their courage and devotion, and we honour their memory by dedicating ourselves to a better tomorrow. Despite the challenges before us today, let us commit ourselves and continue their valiant journey toward a more vibrant and secure future.”

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