As Bret Vyon said, the only ships that stopped there were prison ships from Earth. There were no guards or prison warders. While trying to stop the Daleks' master plan, the First Doctor crashed there on-board the Spar, due to a Dalek tractor beam. The ship had been on route from Kembel to Earth. They took off again, although not before they had picked up a stowaway, Kirksen. (TV: The Daleks' Master Plan) The members of Free Rasta VI were incarcerated on Desperus. (PROSE: Placebo Effect)