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Starbase 47 in 2370
Starbase 47 was a Starfleet starbase that was responsible for new starship developments during the late 24th century.
In 2328, David Trotti traveled from Gamma Towles II to Starbase 47 onboard a transport ship. This information was part of a commercial passenger manifest database recorded in Federation records reviewed by Data in 2370.(TNG: "Inheritance")
In an alternate quantum reality visited by Worf in 2370, Starbase 47 was the object of covert surveillance by the Cardassian Union, who had reprogrammed the Argus Array to observe this, as well as Deep Space 5, the Iadara colony and the Utopia Planitia Fleet Yards. (TNG: "Parallels")
Background information
For more information on this studio model, see TNG studio models. This creates an oddity in design, since Starbases are normally depicted as large facilities capable of supporting and supplying numerous starships, whereas the Relay Station was a very small outpost like space facility holding a crew of only two.
Starbase 47 in Star Trek: Vanguard
In non-canon sources, Starbase 47's 23rd century incarnation is the setting for the Star Trek: Vanguard series of novels.