Engineers at Los Alamos National Laboratory have developed a “license plate” for satellites to help solve the growing problem of space traffic management. The Extremely Low-Resource Optical Identifier (ELROI) is a simple, easy-to-fly, solar-powered beacon that can be attached to a satellite for tracking. Each ELROI unit transmits a custom identification number that can be read from the ground using signal processing techniques also developed at Los Alamos.

The Challenge:

Identifying space objects after launch remains a persistent challenge. When dozens of satellites are deployed simultaneously, determining which object is which using traditional radar or optical tracking methods is slow, error-prone, or sometimes impossible. This lack of real-time, reliable identification hinders satellite commissioning, increases operational risk, and undermines space traffic management efforts.

Unidentified satellites are particularly problematic after their radio systems are disabled or fail. Without continuous, verifiable identification, defunct satellites add uncertainty to orbital catalogs and increase the risk of collision.

Problems Solved:

ELROI solves the space object identification problem by providing an autonomous, low-cost, optical beacon that broadcasts a unique ID from orbit. ELROI:

enables definitive post-launch identification of satellites faster than conventional means;
operates without RF emissions, making it ideal for use even after satellite deactivation;
functions autonomously, activating and broadcasting without requiring power or communication from the host spacecraft; and
continues operation even after satellite passivation, offering a persistent identity signal over the object’s orbital lifetime.

In 2024–25, ELROI was demonstrated successfully on LaCE-1 and R5-S4 satellites, providing the first definitive identification for each satellite in orbit ahead of operator or catalog resolution.

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