The United States National Space Science Data Center catalogued 157 spacecraft placed into orbit by launches, which occurred in 1968. It was the year in which Earth lifeforms first left low Earth orbit, during the successful Soviet Zond 5 mission around the Moon and the Zond 6 lunar mission which crashed upon return. It was also the year that humans first left low Earth orbit, during the successful Apollo 8 mission to the Moon.
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