Lunar V was a moon in orbit of Angosia III. Following the Tarsian War, the Angosian government exiled its veterans to Lunar V because the psychologically and physiologically conditioned soldiers could not adapt to normal society. The original intention was for the moon to be their colony, but some soldiers resisted the resettlement and so the colony was turned into a maximum-security facility.
In 2366, Roga Danar escaped from the Lunar V penal colony to the USS Enterprise-D. He later commandeered an Angosian police shuttle vessel and broke the other prisoners out of Lunar V. (TNG: "The Hunted")