A leave of absence was a period of varying duration in which a member of Starfleet was off duty and not assigned to any posting. The leave of absence had to be granted by a superior officer, who also had authority to recall one into active service. In 2151, Hoshi Sato had a leave of absence to teach at Amazon University, which she ended prematurely to serve aboard Enterprise NX-01. (ENT: "Broken Bow") In 2152, Jonathan Archer offered T'Pol a leave of absence after her second encounter with Menos triggered traumatic memories, but she considered it unnecessary. (ENT: "The Seventh")