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