The array has two exits to the Big MT, one in the upper floors (accessible from the cliffs to the West) and one on the ground floor (accessible from the north), which has an Old World flag painted on it in red (presumably by Ulysses).
The inside of the array has multiple floors, and there is a ladder on the very top floor which allows access to the dish. The top of the dish has one and the only playable X-2 antenna, needed for the quest X-2: Strange Transmissions!.
The inside of the array is guarded by upgraded protectrons. After collecting the X-2 antenna at the top of the dish, some robo-scorpions will spawn inside and outside around the base of the tower.