From Halopedia, the Halo wiki
Office of Naval Intelligence
This unidentified officer was a field operative of the United Nations Space Command's Office of Naval Intelligence. Between 2540 and 2552, he briefed a team of Orbital Drop Shock Troopers and SPARTAN Cal-141 prior to a mission to the planet Heian, which lay deep within Covenant-controlled space. This mission resulted in the assassination of a Covenant Prophet who was responsible for supply routes in that sector of the galaxy.
He was voiced by James Faulkner.