A huge unmanned subspace telescope at the edge of Federation space that malfunctioned after an encounter with an alien probe.
The Argus Array is a massive subspace radio telescope positioned near the border of Federation territory to study distant regions of the galaxy. It is designed to operate without a crew for long periods.
In The Nth Degree, the Enterprise is sent to repair the array after it stops transmitting. An alien probe encountered nearby enhances Reginald Barclay's intellect, and Barclay goes on to use the array's power in plans that eventually reveal the Cytherians, who had drawn the ship to their home near the center of the galaxy.