Just an FYI for those pilots who may be in the midst of this Investigation. The female Gatekeeper Memnon is "invisible" at Arx Tiberius. The male Gatekeeper Memnon at Praetorium Mons, Primus Planet, advanced my mission.
With one less Memnon to remember this mission should be less confusing. There is a mystery: what happened to Ms. Memnon?