Based on the [i]Epoch Class[/i] Carrier(Link Above) it was a prototype ship using alien technology in testing for the UNSC. Later the [i]Infinity[/i] would use these technological marvels fully. They would install technology on this ship from the Covenant and Forerunner Technology. The Ship is Assigned to the 5th Fleet and apart of the Necronomicon Battlegroup. It Returns to Reach after missions or to recive new tech by ONI. ONI uses the ship as a permanent lab/testing ship and they fill a variety of roles in the UNSC testing technology outside the confines of a lab and into practical use. However nothing threatening to the crew has been installed. So anyone and everyone is liable to be on board. The Ship will have it's missions and the crew will have it's assignments. You might be transferred for a time to one of the Battlegroup ships for other missions. UNSC considers all information on the Necronomicon like area 51. You hear rumors but no ones talking. Many think it is a hoax or Ghost Ship. Other than HighCom and it's escorts no one knows it exists. Other secrets will come out as time goes on but for now this is all the information you know.