Rebecca Holmes, Los Alamos National Laboratory; David Palmer, Los Alamos National Laboratory; Michael Holloway, Los Alamos National Laboratory; Charles Weaver, Los Alamos National Laboratory; David Hemsing, Los Alamos National Laboratory; Donathan Ortega, Los Alamos National Laboratory
Keywords: elroi, license plate, beacon, space traffic management, identification
Abstract:
The Extremely Low Resource Optical Identifier (ELROI) beacon is a laser “license plate” for satellites that can be read from the ground using a small telescope and a photon-counting sensor. A reliable way to identify satellites is urgently needed. Over 20,000 objects are currently tracked and monitored in the crowded space around the Earth, and most cannot be easily identified if conventional tracking (which relies on orbit determination) fails. Small satellites such as CubeSats are also being launched in increasingly larger groups, making them difficult to distinguish after launch and presenting a challenge to their operators and to the tracking infrastructure. While there are many proposed solutions, no identification beacon technology has yet become standard or widely used. A challenge is designing a beacon which is both small and light enough for the smallest satellites, and which can operate continuously without conflicts such as RF interference.
ELROI is one concept for a beacon that uses short, omnidirectional flashes of laser light at milliwatt average power to encode a unique ID number. ELROI is powered by its own small solar cell, and can safely operate for the entire orbital lifetime of the host object without needing power or interfering with other systems. The ID number can be uniquely determined from the ground in a single pass, even if the ground station detects only a few photons per second, using single-photon algorithms to isolate the signal and reject background. The ELROI IDs are open and designed to be readable by anyone with a suitable ground station, which requires a small telescope, a spectral filter, and a photon counting sensor such as a SPAD. ELROI also has the potential to be a “black box” for satellites, transmitting low-bandwidth emergency telemetry information if the host satellite malfunctions.
The ELROI concept has been validated in long-range ground tests, and several orbital prototypes have been delivered for (or are progressing toward) launch. We will discuss the design of these prototypes, as well as the next-generation of hardware incorporating new sensors and miniaturized designs, and the data analysis that makes it possible to read a milliwatt signal from orbit. We will also discuss how any interested observers can set up their own ground stations to help observe these upcoming test flights.
Date of Conference: September 15-18, 2020
Track: SSA/SDA