The Nauvoo's unused deep-space communications hardware contains a photon-sensitive signal sniffer the underground repurposes to mirror Laconian traffic.
Medina's communications array was built for the Nauvoo's centuries-long interstellar voyage, making it vastly more powerful and sensitive than current slow-zone operations require. Its forest of antennas, dishes, radio towers, and central laser was intended to reach Earth from one hundred light-years away. Inside a space where nothing lies more than half a million kilometers distant, much of the equipment has never been needed.
Bobbie Draper identifies a dormant field-strength sensor capable of tracking a single photon through a meter-thick fiber bundle. Ramez places its circuits into diagnostic shutdown from operations, and Clarissa Mao physically removes it without triggering alarms. The obsolete generation-ship hardware becomes the core of a passive monitor on the Gathering Storm's dock connection.
A vast exterior cluster of antennas, receiver dishes, radio towers, rigging, and a never-used long-range laser mounted on Medina's bow.
The array supplies the extraordinarily sensitive legacy hardware that makes undetectable interception of Laconian communications possible.