The number of artificial satellites orbiting the Earth has increased exponentially in recent years, from under 1000 in 2010 to over 11,000 today. As the amount of traffic in orbit has increased, so has the risk of collision. Collisions are expensive and create even more orbiting objects, with more than 40,000 pieces of debris now in low Earth orbit.
While the United States Space Force and other agencies track satellites and orbital debris, they can only warn the satellite's operator of an impending collision if they know who owns it. Rockets sometimes launch dozens or hundreds of satellites simultaneously, making identifying and tracking them much more labor intensive.
Los Alamos National Laboratory has developed the Extremely Low Resource Optical Identifier, or ELROI, as a "license plate" for satellites. The postage stamp-sized device has a solar-powered rechargeable battery and a laser that blinks in a unique pattern that a small Earth-based telescope with a photon-counting sensor can read.
Because the system is not radio based, RF interference is not an issue. ELROI successfully identified satellites during two launches in 2024. An abstract from 2018 estimated costs of approximately $500,000 per base station and $1000 per spacecraft.
Previously: International Space Station evades space junk
