Payload adapters for launch vehicles include a ring structure having an opening formed therein and at least a portion of an antenna assembly coupled to a circular sidewall of the ring structure at least partially within the opening of the ring structure. Satellite assemblies may include a payload adapter comprising a ring structure having a circular opening formed therein and an antenna assembly including a parabolic reflective dish formed within the circular opening. Launch stack systems may include a primary payload and a secondary payload adapter including an antenna dish integrally formed with a ring structure of the secondary payload adapter. Methods of forming a satellite assembly include positioning at least a portion of the antenna assembly within an opening formed in a ring-shaped payload adapter for a launch vehicle and coupling the at least a portion of the antenna assembly to the ring-shaped payload adapter.