Early Warning Sensor System

From FEInfobase

The Early Warning Sensor System or E.W.S.S is a network of probes, listening stations and unmanned monitoring bases set up near Pluto in the Sol system. It was brought online in 2398 by Starfleet who uses it to determine if there are any threats uproaching the system. In 2402 the USS Enterprise-F was picked up on the E.W.S.S when it returned to Earth (DS1: "The Miracle Workers").