In looking at the location of Pixie on the Traveller Map, a couple of things jump out at you. One, it is on the border with the Vargr Extents, and two, it is also very near the border with the Zhodani. Therefore, the Navy Base with a "D" Tech Level and Class "A" starport make sense. The base is not going to be too large, because of its exposed position, but should have enough capability to act as a substantial trip-wire to any attack.
Next, Pixie is only a thousand miles in diameter, is airless and has no water. The system does have a Gas Giant. Based on that, with the requirements of the Navy Base for adequate fuel supplies, Pixie should be orbiting the Gas Giant. Part of the base equipment will be scoop ships diving into the Gar Giants upper atmosphere and collecting fuel. So far, so good.
I would figure the population of a small naval base at roughly one to two thousand, with dependents added to that, so maybe 6,000 total for the base population. The Class "A" starport, in theory, should be able to built ships, but in this case, it might be restricted to building only small ships with major components shipped in. Repair and refueling would not be a problem. There would likely be a mix of surface dome installations combined with underground installations, storage, and living space. The whole base would be under Naval control and discipline, so whatever Law Level would fit with that, with a government level for the base of either "1", Company/Corporation, or "6", Captive Government. I would argue for "6", but that is open to discussion.
The anomaly for Pixie is that the population and government type do not match would I would view as appropriate for the Naval Base. I am not sure about the Law Level. Presumably, the starport is also open to civilian traffic, as I cannot see that low a population running an Class "A" facility. To make the existing description work, the population of the Naval Base is not included in the given population exponent. What is most likely is a small number of either ex-Navy or retired Navy living in former Navy facilities, left over from previous wars, who are mining the surface of the planetoid for ice pockets and other useful minerals such as nickel-iron meteor impacts and stony meteor impacts containing needed carbon for hydroponic plant growth in the base, and other small quantities of useful minerals. I would argue that this might be the best explanation, as it gives some permanence to the settlement.
Optionally, the population number may reflect an archaeological team investigating a possible Ancient site, as mentioned in the Wiki. The team draws on the Navy Base for support in its operations. The starport is open to use by civilian shipping, but exploration by civilian ship crew off of the starport is not encouraged. The Navy Base population does not figure in the population exponent. The problem with this is that is does not really give a permanent settlement on the planetoid.
I do not see it as a prison, as the government type and Law Level do not fit at all. Now, having the "Gash" in orbit around the planetoid does not make the world itself a prison, and the "Gash" crew and guards would come from the Navy Base.
That is basically how I would explain Pixie, if I had to do it without changing any of the publish data. Personally, I would put the Naval Base population into the data, and change the government type. I probably would also change the Law Level 4 or so, to allow for sidearms to be carried on the base.
That is my input, for what it is worth.
