An aerostat is a device which remains in a geostationary position within the atmosphere of a planet. Dr. Marat Lon designed a network of aerostats to clear the atmosphere of planet Mestiko from contaminants. (TOS - Mere Anarchy eBook: The Darkness Drops Again)
- Curiously, while Lon makes it a point to correct a Payav who calls his aerostats "satellites" in The Darkness Drops Again, he himself calls them satellites in The Centre Cannot Hold. It may be conjectured that his devices were capable of operating as both at different stages of the mission.