CubeSat-based Space Laser Terminals

Kurzfassung

The ongoing development of spaceborn instruments generating increasingly amount of data, such as higher sensor resolution, dynamic range or their quantity in a satellite, leads to the demand of a higher downlink rate from space to a ground station. Commonly used RF systems need a license, are limited in bandwidth. Beside that, they require a non-negligible amount of space, weight, electrical power and cost which is in particular critical for small satellites such as CubeSats. To overcome these drawbacks, the DLR Institute of Communications and Navigation has developed OSIRIS4CubeSat - a 1/3 U CubeSat laser-communication terminal for up to 100 Mbit/s downlinks1. It has been launched in January 2021 on the 3U CubeSat PIXL-1 [1] that takes high resolution images and transfers them to an optical ground station. The terminal is equipped with a closed loop tracking system for sustaining a stable link. Beside speed, another important aspect of data communication is its security. For future quantum-safe networks, satellite-based QKD is a key. The exponential decay in optical fibre limits the exchange distance to several hundred kilometres with reasonable key rates. In an optical free space link, the channel loss is quadratic to the distance. Therefore, satellite links are needed to interconnect quantum safe networks over large distances. For a cost- and time efficient development, a CubeSat-based approach is feasible to realize a QKD-Satellite. In the framework of the QUBE consortium [2,3], we develop a 1/3 U laser terminal to be used for quantum communication tests at wavelengths of 850nm and in the C-band. In order to meet the challenge of an achromatic design for the compact free space optical system, a compromise between beam divergence and tracking performance is made. A further development of this demonstrator will enable quantum key exchange. In the QUBE II [4] consortium we will develop a laser terminal with a larger aperture for an increased link budget. This implies higher demands on the overall optical design and especially on the tracking system. Sources: [1] Rödiger et. al., "High data-rate optical communication payload for CubeSats", Proc. SPIE 11506, IX, 1150604 (22 August 2020) doi: 10.1117/12.2567035 [2] Haber et. al., "Fundamentally Secure Data with the Help of Quantum Key Distribution on CubeSats", Proceedings of the International Astronautical Congress, IAC, 21.-25. Oct. 2019, Washington. ISSN 00741795 [3] Federal Ministry of Education and Research, "QUBE - Sichere Satellitenkommunikation mit Quantenschlüsseln", Web presence: https://www.forschung-it-sicherheit-kommunikationssysteme.de/projekte/qube [4] Federal Ministry of Education and Research, "QUBE II - Kostengünstige Quantenkommunikation per Satellit", Web presence: https://www.forschung-it-sicherheit-kommunikationssysteme.de/projekte/qube