The Watchtower satellite network is a system of highly advanced United Nations Navy (UNN) spy satellites. These satellites are uniquely equipped with advanced sensor technology able to penetrate Martian stealth technology. They are one of the most advanced and valuable assets available to the UN (United Nations).
During the UN-MCR War, Watchtower-14 was responsible for locating and identifying two MCRN Stealth C ballistic missile platforms—this was considered a tactical breakthrough, as it proved instrumental for the UN to identify the locations of the other three platforms. The spotting of these stealth missile platforms allowed for an attempted first strike ordered by United Nations Secretary-General Esteban Sorrento-Gillis against the first-strike capable stealth nuclear missile Martian platforms.
Following the initial two asteroid impacts on Earth—a part of belter radical Marco Inaros' attack on the inner worlds—, the Watchtowers were re-tasked on order of Secretary-General Nancy Gao to link with the Sentinel asteroid spotters and spot additional inbound asteroids. This was necessary—and very critical to Earth—as these asteroids were stealth-coated, leaving the Watchtowers to defend Earth in this capacity. This order would, however, prove to be Gao's last, as shortly after doing so, UN One was knocked out of the sky by the blast wave of a third asteroid near the Bay of Bengal; all aboard are presumably killed.
Although Gao ultimately perished in the crash, the order was indeed effective; a fourth asteroid, headed for the North American western seaboard, was spotted by the Watchtower-Sentinel network. This allowed for two orbital railguns to shatter the asteroid, with a Leonidas-class battleship in orbit vaporizing the remains with a volley of missiles. It can be assumed from later reports aboard Pella that two other asteroids shared the same fate.