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Deep Space 5 in 2370
Deep Space 5 was a Federation space station located near Ivor Prime in the late 24th century, responsible for new starship developments.
In an alternate quantum reality visited by Worf in 2370, Deep Space 5 was the object of covert surveillance by the Cardassians, along with Starbase 47, the Iadara colony, and the Utopia Planitia Fleet Yards. (TNG: "Parallels")
In 2373, Deep Space 5 reported the complete destruction of the colony on Ivor Prime. It was subsequently determined that the Borg were responsible, and were mounting a new attempt at an invasion of the Federation. (Star Trek: First Contact)
Apocrypha
In the Star Trek: New Frontier novel series, Deep Space 5 is located near Sector 221-G, a region of space that included the planets Danter and Xenex and the former Thallonian Empire. The station was under the command of Admiral Edward Jellico. The USS Excalibur launched from Deep Space 5 on its mission to render humanitarian aid to Sector 221-G.