https://www.mdu.se/

The emergence of quantum computing presents a new frontier in secure communication. However, while the early adoption of quantum applications, such as quantum key distribution, in satellite communications addresses the security challenges posed by this next-generation technology, it also introduces additional challenges. These include the necessity for large-scale satellites and ground stations, as well as limitations in the number of quantum keys that can be generated. In response to this situation, we developed SeCRETS1 (SeCuRe lasEr communicaTionS terminal for Low-Earth Orbit (LEO)), which is a highly confidential cryptographic communication device deployed on the exposed segment of the International Space Station (ISS) in August 2023. A redundant configured On-Board Computer (OBC) for SeCRETS has been revealed in this paper. The utilization of a redundant CPU and Ethernet Hub in the OBC plays a pivotal role in fortifying the overall reliability. In tandem with this selection, the following requirements have been considered and performed to design, manufacture, and experiment with the OBC of the SeCRETS. First, the implementation of power control functionality within the redundant OBC, with a focus on prioritizing laser safety, has been prioritized. Second, the incorporation of a redundant-configured hub to establish a highly reliable Ethernet network has been included. Lastly, adhering to ISS demands, provisions have been made for power supply to the primary power distribution machine and other associated devices. This paper comprehensively delves into the intricate details of this groundbreaking technological advancement including the experiment results on Earth and in-orbit.