UNSS Arcturus were three Terran starships of the 21st and 22nd centuries. ("The USS Arcturus in History"; Star Trek: Shadowstar Station) The first UNSS Arcturus was a DY-500-class vessel that made the first Earth-Saturn voyage under the command of Colonel Shaun Geoffrey Christopher. Arcturus, with a crew of 40, was launched in 2018 and entered orbit of Titan on 31 March 2025. (Col. Christopher and his expedition are mentioned in TOS: "Tomorrow is Yesterday") The continuity of Expanding the Oecumene refers to this patrol sector as Sector Zero.