A Planetary Security Intelligence is a type of Artificial intelligence construct in service with the UNSC. One such P.S.I. is Loki, who served on the UNSC Skidbladnir. They are generally kept secret by, in one case, swapping positions with another A.I. They help conduct defense operations and evacuations in the event of an invasion of a UNSC colony by Covenant forces, an example of such being the first Covenant invasion of Harvest.