Captain Mitchell was the commanding officer of the Earth colony ship SS Conestoga.

In 2069, Mitchell lead a group of colonists to the planet Terra Nova to establish the first extra-solar Human colony, which was established in 2078.

Mitchell was among the last Human survivors of the radiation fallout that destroyed the colony following an asteroid impact near their settlement. Mitchell attempted to send a distress call back to Earth, but the radio message was blocked by the fallout and never received.

The fate of Mitchell and the Nova colony was not discovered until 2151, when the planet was visited by the Earth starship Enterprise NX-01. (ENT: "Terra Nova")

Mitchell's voice was provided by an unknown actor.
According to the book Star Trek: Federation - The First 150 Years, his full name was Andrew Paul Mitchell.