From Halopedia, the Halo wiki

Opusculus is one of the eight satellites, and the only natural satellite, of the gas giant Substance in the Coelest system. It is adjacent to Installation 05.[1] During the Battle of Installation 05, the UNSC Dusk hovered in the shadow zone of the moon to monitor the Covenant ships fighting amongst themselves over Installation 05.[2]

List of appearances[edit]