Indeed, I guess any preposition in Latin can be assumed to be at least superfluous if not outright in error... Putting "planets" in the possessive form should suffice. That is, if we assume that "planets" is possessive, rather than descriptive.
It's the old "United States of America" problem again. Is it a bunch of States that are United and possessed by / located on the continent of America? Is it a bunch of States located in a nation of America that almost coincidentally sits on the continent of America? Is it a bunch of States defined as America?
United Federation of Planets is unlikely to be a nation named Planets that possesses a Federation. But do the Planets possess the Federation, or does the Federation consist of its Planets? Is this one Federation of Planets out of many, including the Dispersed and the Indifferent?
Semantics like that won't be solved by looking at the English version. But doing it in Latin would require the issues to be solved first...