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Autonomous illumination payloads on-board small satellites, i.e. LED (Light-Emitting Diode) boards on CubeSats, can be tracked by ground-based telescopes for optical identification, orbit determination and attitude determination. The concept has been explored through the LEDSAT 1-Unit CubeSat project, conceived by Sapienza University of Rome and University of Michigan, and generalized for implementation on all the satellite form factors and classes. The first CubeSat that was launched with LED-based payloads on-board is WildTrackCube-SIMBA (International Designator code 2021-022 K, NORAD identifier 47 941), conceived by Sapienza University of Rome, Machakos University and University of Nairobi. The spacecraft was launched on March 22, 2021, while LEDSAT has been launched on August 17, 2021. This paper describes the proof of concept of LED boards tracking performed with blue LEDs (449–453 nm) installed on-board the WildTrackCube-SIMBA 1-Unit CubeSat. The observations results provide the identification of the object among the numerous satellites released by the same launcher and the recognition of the flashing pattern and satellite face. The results validate the concept of the usefulness of such payloads on-board small satellite platforms, while the upcoming mission LEDSAT will extend the investigation significance by performing extended operations with an enhanced LED-based payload. • The WildTrackCube-SIMBA 1U CubeSat blue LED boards have been observed with telescopes at ground. • The LED boards are developed within project LEDSAT, demonstrating the effectiveness of LED-based payloads on-board a CubeSat. • The first observations allowed to identify the object among all the satellites deployed within the same launch. • The acquired optical data were processed to identify the satellite and to recognize the flashing pattern. • More investigations will be carried out by LEDSAT, carrying LEDs as primary payload and launched on August 17, 2021. [ABSTRACT FROM AUTHOR]

With the increasing number of satellite launches, especially in Low Earth Orbit (LEO), optical tracking can offer a convenient enhancement of tracking precision and availability. Spaceborne active illumination devices, such as LED payloads, can offer a significant improvement to optical observations, extending the observability interval to the whole eclipse time and performing optimized flash sequences for identification, orbit determination, attitude reconstruction or low data rate communication. The main features of LED panels for optical tracking mounted on small satellites platforms (and with particular regards to nano-satellite platforms) are outlined in this paper, along with the description of the design drivers. The analysis of the performance is referred to Sun-Synchronous (at 700 km of altitude) and International Space Station (400 km) orbits, while the ground segment and the optical link budget reference design relies on a standard university space debris observation station architecture. The paper also outlines the advantages of using different observation techniques and the variety of flashing patterns. The LEDSAT 1U CubeSat, aiming at demonstrating the effectiveness of an LED-based payload for observation and tracking, is used as a study case for examples of the LED payloads and related operations that are reported and described in this paper. • LED payloads on the external surfaces of satellites could enhance tracking. • Budget and major design drivers for LED boards on spacecraft are presented. • Early identification for cluster launches will be enhanced by LED flash patterns. • Besides orbit and attitude determination, LEDs can perform back-up communication. • The paper uses the LEDSAT 1U CubeSat as study case. [ABSTRACT FROM AUTHOR]