- You may be looking for the likely unrelated planet.
Phoenix was an Earth colony on a planet in an obscure region of space, quite remote to Earth itself. It was founded by human pioneers seeking independence from the Federation in 2835. The planet was terraformed to make it hospitable for the colonists.
At the time that Peri, the Fifth Doctor and Erimem visited it, it was a failed colony comprised of just sixteen individuals — including Bellip, Vidler and Laroq — and led by Auntie. A space station called Medusa orbited the planet and therefore the colony.
A principal feature of the colony was the fact that its inhabitants were kept in extreme personal isolation from each other. They rarely left their own rooms, leading them to develop extreme agoraphobia. (AUDIO: Three's a Crowd)