Commodore Probert's name was an inside reference to Andrew Probert, one of the illustrators who worked on the film and, later, the designer of the USS Enterprise-D. (Star Trek Encyclopedia) Chronologically, Probert's rank was the last known use of the rank of commodore as applied to a Starfleet officer.
Andrew Probert himself recalled, "The communications station "Epsilon-9" was briefly looked at but the design and building went to John Dykstra's Apogee group. I had a second brush with that station however, when Trumbull asked me to write some appropriate dialogue to run over scenes of the station as background chatter. This introduced the station without a big sign hanfging on it. I wrote several levels of dialogue and even stuck my own name in a lower level, but when Trumbull saw it, he had that level moved to the top, and you can hear a message from Commodore Probert if you listen closely." (Starlog photo guidebook Special Effects, vol. 5, p., 96)