Extremely Low Resource Optical Identifier

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.

• Ultra-Low SWaP-C (Size, Weight, Power, and Cost): Final designs aim for just a few grams and a few cubic centimeters, requiring minimal power.
• No RF Interference: Uses optical rather than radio frequency, sidestepping spectrum crowding and regulatory issues.
• Autonomous and Passive: No spacecraft support required; beacon runs independently, even on dead satellites.
• Fast and Robust Identification: High-confidence decoding of unique identifiers using ground-based photon counting techniques, even with low signal strength.
• Scalable and Flexible: Can be added to any space object, including CubeSats and deployable debris, without complex integration.
• Resilient Design: Uses robust encoding schemes (e.g., BCH error-correcting codes) to ensure ID recovery under high noise and low signal conditions.

• Space Traffic Management: A standard beacon on all space objects reduces uncertainty, supports catalog maintenance, and improves deconfliction.
• Regulatory Compliance: Enables better enforcement of norms and international transparency for satellite tracking and ownership.
• Mission Assurance: Helps satellite operators confirm identity quickly after deployment, expediting commissioning and reducing risk.
• End-of-Life Management: Provides lasting identity for passivated or tumbling satellites, supporting sustainable space practices.
• Commercial Launch Services: Can be included as standard hardware on launch platforms to simplify post-launch operations for clients.

For ELROI to become a standard part of space operations, three parallel tracks must advance:

1. Beacon Manufacturing: Move from prototypes to production-scale manufacturing of standardized, miniaturized ELROI units.
2. Ground Network Expansion: Establish a distributed network of ground stations using cost-effective photon-counting or hybrid imaging systems.
3. Operator Adoption: Encourage satellite operators to integrate ELROI through demonstrated benefits, policy incentives, and regulatory encouragement.

Widespread use will grow as ELROI proves its value, stays low-cost, and gains support for improving space safety.