Major Vaughan's command squad, callsign Sunray 1-1, is the lead element of Boomerang Company, the UNSC's most elite force of Orbital Drop Shock Troopers [though that's what they all say].
UNSC Navy Medic.
Petty Officer Gruss is the Navy combat medic assigned to Major Vaughan's command squad. A woman of [very] few words, the ODSTs make it their mission to interpret "Doc's" opinion of their shenanigans by analyzing her body language, sighs, rude gestures, and grunts of disapproval. This friendly harassment ends when combat begins, for Doc holds the lives of the troopers in her able hands, wielding biofoam and trauma packs across the squad's position with incredible skill and delicacy. So perfect is her timing in dealing with injury that it borders on the prescient, and squad members resign themselves to the inevitable if Doc appears near them during battle.
In addition to her medical skill, Gruss has shown a remarkable talent for escape and evasion by avoiding the Marines' many and varied attempts to induct her into their ranks as an honorary Helljumper. This irks some members of the battalion, but even ODSTs are not crazy enough to risk the ire of a medic [and Major Vaughan] by pressing the issue. When deployed with the command squad Doc patches up the team's injuries with her medkit.