This article discribes an existing Fallout 3 Vanilla/DLC character that is modified/referenced by the Mothership Zeta Crew mod. For more information, see the Nukapedia article about Elliott Tercorien
Elliot Tercorien, AKA Dr. Tercorien, AKA Private Elliot Tercorien serial number 3477809; was, along with Sally, was one of the original abductees that helped The Lone Wanderer take control of the ship during the former's insurrection.
Prior to the war, Elliot Tercorien worked in a hospital as a doctor, before being drafted into the (in)famous operation to retake Alaska from the Chinese.
He and the rest of his squad were abducted by the aliens while serving in the U.S. Military, just prior to the Great War during the Liberation of Anchorage.
When the man that would later become The Commander first encountered and unfreezed Elliot, the former medic was rather leary and suspicious of the Lone Wanderer, thinking him working with the aliens, but nonetheless Elliot eventually relented when he realized the obvious.
He then assisted the Lone Wanderer in destroying the generator in the Cryo Labs, but not before finding the remnants of his squad and having to face a hard decision about what to do with the survivors.
TSC History does not document what that decision was.
Eventually, Elliot, along with the Lone Wanderer, Paulson and Somah , reached the bridge, where they were forced to fight off an incoming alien ship and boarders. Eventually, and miraculously, they succeeded in destroying the craft.
While Somah left to find her fortune, and Paulson left for reasons unknown, Elliot opted to stay behind on the ship along with Sally. He had nowhere else to go now that everything he'd ever known was destroyed, and quite certainly wanted absolutely no part of the hell the wastes had to offer him.
When Harkin and his crew of Enclave defectors/outcasts moved in at the Lone Wanderer's invitation, Elliot assisted the newcomers with the task of figuring out the alien's technology. Why exactly he did this is unknown, possibly either out of sense of loyalty to the Commander, a sense of nostalgia regarding what was left of his old government, and/or just wanting to make himself useful and avoid a fight.
Whatever his reasons may have been, his help to both the newcomers and to the Commander himself during his takeover of Mothership Zeta was so well appreciated that he was made an honorary officer in the newly founded TSC, and to this day remains on the Olympus.