"Orion began its journey to Earth by launching its engine on Dec. 1 to leave lunar orbit thousands of miles above the Moon's surface," the U.S. space agency's website said in a statement.

The press service reported that engineers are testing systems to improve understanding of the operation of the ship in anticipation of future missions with astronauts on board.

The spacecraft is expected to splash down in the Pacific Ocean near San Diego on December 11.

On November 16, NASA launched the Space Launch System (SLS) super-heavy launch vehicle with the Orion spacecraft as part of the first stage of the Artemis 1 lunar program.

In July, NASA announced that the launch of the commercial VIPER rover to the Moon was delayed until 2024.