Screenshot of a tweet posted by Matthias Maurer, a German European Space Agency astronaut on Oct. 15, 2021. (Xinhua)

As the Shenzhou-13 spacecraft astronauts entered China's space station core module Tianhe and began their mission, foreign astronauts sent warm greetings and wishes to their fellow friends in space.

Some of the foreign astronauts took training programs in China and established good friendships with their Chinese colleagues.

"I will join you soon in space," wrote Matthias Maurer, a German European Space Agency astronaut.

Screenshot of a tweet posted by Ricky Arnold, a retired astronaut of U.S. space agency NASA, on Oct. 17, 2021. (Xinhua)

Screenshot of a tweet posted by Chris Hadfield, a retired Canadian Space Agency astronaut on Oct. 16, 2021. (Xinhua)

Screenshot of a tweet posted by of Chinese Ambassador to the United States Qin Gang about an interview with Cady Coleman, a retired astronaut of U.S. space agency NASA, on Oct. 18, 2021. (Xinhua)