Huge space station near Klingon space in 2271 designed to track and report any unusual activities.

Epsilon IX was Starfleet space station serving as a massive radio antenna near the Klingon border in the mid 23rd century. Epsilon IX was located in close to the Scylia sector, and while used to spy on Klingon activities, it also served as a subspace communications rely station. In the 2271, under the command of Commander Branch, the station was destroyed by the machine-lifeform V'Ger after attempting to communicate with it.

Viewed from the exterior, Epsilon IX was made up of symmetrical panels interspersed with a number of differently sized antennas and receivers, making the whole station one giant communications reflector. A monitoring room, the operational heart of the station, sat near the top of the array. The room was filled with consoles, viewscreens, and sensor equipment, and was open-plan, making it easy for the technicians to coordinate their efforts.

Some of the operators worked at standing consoles, while others sat at individual work station along the walls. The touch-sensitive consoles displayed various schematics, and information on any starship activity or unusual spatial phenomena. The viewscreens were capable of showing activity that was picked up by sensors or probes, while a written record of any verbal communications could be featured on a separate screen. The computers were also capable of providing a verbal translation of any known-alien-language transmissions that were intercepted. The station was able to relay realtime pictures and messages to Starfleet or any appropriate starships.