Arkaria Base was an outpost located on the planet Arkaria that controlled the orbiting Remmler Array, used for baryon sweeps. The base was run by Starfleet Commander Calvin Hutchinson until 2369, when he was murdered.
The plains surrounding the base made for excellent horseback riding and Jean-Luc Picard took advantage of this as an opportunity to excuse himself from an invitation to a reception hosted by Commander Hutchinson. (TNG: "Starship Mine")
Arkaria Base was a reuse of the matte painting first seen as the Darwin Genetic Research Station in "Unnatural Selection".
As it had not been clarified on screen whether Arkaria was a Federation member world, it remained unknown if Arkaria Base was a full Federation facility or only administered by Starfleet. The Star Trek Encyclopedia, 4th ed., vol. 1, p. 45 identified the Arkaria Base as a Federation facility.