When he reached the age of 18, he applied to Starfleet Academy and was accepted. He immediately began studies in the Engineering track, excelling in all his classes.

During his time at the Academy, he met Vanessa Tannley, and the two had a rather serious relationship.

After graduating from the Academy, he was assigned to the U.S.S. Atlantis as an Assistant Engineer and separated from Vanessa, who was assigned to the U.S.S. Beowulf. During his time on the Atlantis, he distinguished himself among his superiors, especially on one occasion, where he saved the ship by coming up with the idea to reroute the damaged power transfer conduits through evacuated turboshafts. Because of his cool head during battle and his creative solution to the near-destruction of the ship, Cathero was promoted to Lieutenant, junior grade, and transferred to the Potomac as Chief Engineer. On his way to the Potomac, he received word that the U.S.S. Beowulf had been destroyed in a battle with the Dominion. Jem'Hadar ships had surrounded and overpowered her before she could escape. This news caused him great grief and for a time he seriously considered resigning his Starfleet comission. When he took a moment to step back and really look at the issues, though, he relented and accepted his assignment to the Potomac.