The Mandela was a human colony ship which set off from Earth in 2059. Billy Inyathi Forrester Obote was in cryogenic suspension on board the ship. (PROSE: Heritage) At some point, the Mandela passed the orbit of Pluto. (PROSE: Second Chances)
Behind the scenes
Although it was not stated specifically in either story, it is highly likely that the vessel was named after Nelson Mandela.