Captain Samantha Carter first appears in " Children of the Gods ", the pilot episode of Stargate SG-1, as a United States Air Force captain who joined the fictional SG-1 team under the command of Colonel Jack O'Neill. After being promoted to major in Season 3, Carter remains O'Neill's second-in-command until her promotion to lieutenant colonel early in Season 8, at which point she assumes command of the SG-1 team and O'Neill is promoted to brigadier general in order to lead Stargate Command. Between Seasons 8 and 9 of SG-1, following the defeat of the Replicators and downfall of the Goa'uld system lords, she accepts a position as Head of the Stargate Research and Development Program, based in Nevada. She is engaged in deep-space research when the Ori emerge. Upon her return to Earth, she is reassigned to SG-1, now under the command of Lieutenant Colonel Cameron Mitchell. Following the defeat of the Ori in Stargate: The Ark of Truth, Carter is promoted to full colonel and appointed as commander of the Atlantis expedition early in Season 4 of Atlantis. Carter is later given command of the Daedalus-class ship, the George Hammond.