A geosynchronous orbit (GSO) is an Earth orbit where the orbital period matches the Earth’s rotation. There is a special case of a GSO called a geostationary orbit where a circular GSO has no inclination to the Earth’s equatorial plane and is directly over the equator at an altitude of about twenty three thousand miles. A satellite placed in a GSO will remain stationary with respect to a location on Earth.
Arthur C. Clark, a famous science fiction author, was the first to propose using this orbit for communication satellites. In honor of Clark, this is referred to as the Clark Orbit. The approximately six hundred artificial satellites in this orbit are referred to as the Clark Belt.
When communication satellites are launched into the Clark Orbit, many of them carry enough maneuvering fuel to adjusts their orbits for about fifteen years. At the end of that time, the satellites are considered to be non-functional because they can no longer precisely control their orbits which is necessary for them to serve their purpose. They become space junk and take up valuable slots in the Clark Orbit which is rapidly filling up.
Many of these satellites are still perfectly functional as far as their internal electronics are concerned. If some way could be found to restore orbital maneuverability, they could once again become fully functional. A company called Effective Space has been working on a way to accomplish that.
Effective Space has designed a space-faring drone that weighs about nine hundred pounds. Once launched into geostationary orbit, the drones would seek out satellites that had run out of fuel. Even though the target satellite was not designed for docking, the drones would be able to attach to the interface rings that attached the satellite to its launch vehicle. Once the drone and the satellite are joined, the drone can use its ion thrusters to maneuver the satellite and restore it to full functionality.
When the onboard electronics of the drone-connected satellite finally fail, the drone would steer it into what is called a “graveyard orbit.” The satellite would then spiral in and burn up as it entered the Earth’s atmosphere. This has the added benefit of freeing up one of the precious Clark Orbit slots. The drone would detach from the satellite and move on to another aging satellite. The lifespan of a typical drone would be about fifteen years. When it was nearing the end of its life, it too would descend and burn up before it ran out of fuel.
There are other companies that are entering the drone refueling marketplace. Orbital ATK has a contract to use drones to save a couple of communication satellites. Effective Space feels that the small size of its drones will give it an edge against the competition.
Although fiber optics are replacing communication satellites in densely populated areas on Earth, the Clark Belt will be crowded in the foreseeable future and drone maneuvering systems will be important.