Petty Officer Third Class
(Abbreviated to PO3) is the lowest Starfleet non-commissioned officer rank. Petty Officers Third Class generally serve as relief personnel to another post, such as transporter operator. Petty Officers are journeyman level specialists within a field. A petty officer may be addressed by their job title, such as Hospital Corpsman Third Class, or Torpedoman's Mate Third Class, as well as by the generic title of Petty Officer. A PO3 takes a fleet-wide exam for advancement to Petty Officer Second Class.