The Callisto Penal Colony was a space colony in orbit around the Jupiter on the moon of Callisto which housed approximately 1,600 inmates. It was captured by the Free Fleet sometime in the 23rd Century beginning the After Earth Era.
Before the arrival of the Free Fleet, Callisto served as an orbital penal colony for dangerous Human criminals. Shortly after the Earth was hidden with the help of the De'rem, those left behind revolted and took control of the colony. Not long after the insurrection, the colony was captured by Commander Mezer Juul of the Free Fleet and its inhabitants were treated as live stock to be sold to the highest bidding alien race.