6
NASA's Voyager 6 probe was launched from Earth in the late 20th century. It fell through a convenient black hole and wound up on the other side of the galaxy. Found by machine aliens (which in William Shatner's novels were the Borg but in everyone else's novels not), it was given sentience and the ability to carry out it's mission - "to learn all that is learnable". 300 years later, believing itself successful, it returned home.
Luckily, Admiral Kirk had Commander Decker nearby to have freaky light show sex with V'ger (currently embodied in a robotic duplicate of Decker's ex) and the pair of them evolved to a higher plane of existence. Or something. Everyone lived happily ever after until Khan came back and then Spock died for a bit. But it all turned out okay.