The Mission to Installation 03 was a UNSC operation to investigate the loss of contact with a science outpost and Spartan-II Black Team on Gamma Halo immediately following the New Phoenix Incident in July 2557. Spartan-II Blue Team, having just been reunited after the return of John-117, were sent to Installation 03 to determine the status of the outpost, only to find that all UNSC military and research personnel, including Black Team, had been killed. Blue Team also discovered that the Ur-Didact, who had been sent into a slipspace portal during the battle on Mantle's Approach above New Phoenix, had been sent to Installation 03, and was the cause of the death of the humans on Gamma Halo. Fighting ensued between Blue Team and the Ur-Didact, who was attempting to take control of Gamma Halo and use it on Earth. With the help of the monitor in charge of the composers, 859 Static Carillon, Blue Team successfully stopped the Didact from taking control of the halo and managed to compose him.