Orbital Weapon Platforms

Satellites with big lasers on.
In terms of relevance to the story, they play a role in planetary quarantine, a protocol rarely needed. If a planet is discovered to be host to a disease which is dangerous, contagious, and has few or no treatment, a quarantine is declared on the whole planet. Weapons platforms are deployed in a lattice in orbit, so the whole planet is covered. The purpose of these platforms is to destroy any craft which might attempt to leave the planet without authorization, to contain the disease.
Such a system was deployed over the skies of Planet 237-121 once the outbreak of the Fungal Disease was confirmed.
This created fear and paranoia within the surviving colonists, as they are cut off from the rest of the empire.

Social Impact

The violent enforcement of the planetary quarantine sparked further fear among surviving colonists. Some went so far as to say this proves the Empire knew about the disease even before the humans were resettled there.

Access & Availability

Because of the sheer power of such weapons, they're tightly controlled by the Empire and only deployed when absolutely necessary.

Discovery

These orbital weapons systems existed before the Victory of the Machines, but are still utilized by the Steel Empire.