Observation Deck

The  is a location on board Mothership Zeta.

About
This area is initially referenced in the Engineering Bay where there is a deactivated teleporter to it. It is my assumption that this teleportation pad becomes active after the completion of the entire Mothership Zeta questline, though it is possible it is reactivated earlier than that.

I believe the Observation Deck is first accessed after the space walk and is likely the room with the large glass floor through which the Lone Wanderer and NPC companions witness the Aliens firing their Death Ray towards Earth as a threat to come no nearer to The Bridge.

These assumption requires confirmation.

Appearances
only appears in the Fallout 3 add-on Mothership Zeta.