From Halopedia, the Halo wiki
By 2531, Gibson was head of ONI Section Three's Black Operations division, which was described as the "hands-on wet-work" counterpart to Covert Operations, the section of ONI headed by Rear Admiral Rich. As a field officer, he suffered from "Space walk."
In 2531, Gibson, Rich, Vice Admiral Margaret Parangosky, and Colonel James Ackerson met aboard the UNSC Point of No Return to discuss the SPARTAN-III project. Gibson, being jealous, was very much opposed to the SPARTAN-IIs, frustrated by their success, as opposed to that of his own projects. He favored the proposal of a third-phase SPARTAN project and gave the go-ahead for it to begin.
The ONI Memorial in Halo 3: ODST mentions Gibson in a list of deceased ONI personnel; however, given that the plague lists all ONI members who had been named at the time of the game's release (including Margaret Parangosky, who was later established to have been alive and leading ONI at the time), it can be considered to be of dubious canonicity.
List of appearances