Spyglass was the name of a Terran Federation surveillance technology.
It was the net of passive surveillance satellites, stretched around the periphery of a star system's hyper limit. In case of an attack, they were to beam their imagery to the courier vessel that then left the system.
When Crestwell's Star came under attack from the Gbaba, the defense forces implemented Spyglass along with the Watchman system. The satellites successfully transmitted their data to TFNS Gazelle, a courier that was to remain hidden until the end of the battle and then report back to Earth. (OAR)