Gay is Moonbase's Chief Space Tracker and one of several Moonbase Commanders, assuming responsibility for the base in the absence of a superior officer.
She recently developed a relationship with Interceptor Pilot Mark Bradley. She drinks her coffee without sugar.
Lt. Ellis was known to have been serving in S.H.A.D.O. as early as 1980, the time frame of the programme, and was in field command of MoonBase when the first UFO successfully evaded the MoonBase Interceptors and actually reached Earth.
Gabrielle Drake acted out the role of Ellis in the programme.