Several operators plan to launch mega-constellations of several hundred or even thousands of satellites over the next years to provide global, high-speed and secure backbone communications. Most of these constellations will use a hybrid approach, with radio links for communications with the ground and free-space optical communications for inter-satellite links. First demonstration satellites were successfully launched in 2018. Since 2009 Mynaric has successfully demonstrated high-speed laser communications in air-to-air, air-to-ground and ground-to-ground applications. Data rates up to 10 Gbps were achieved and altitudes up to 20 km were reached. First airborne terminals and ground stations for airborne and space applications were delivered to commercial customers. Building on the heritage from operations in the harsh environment of the stratosphere, Mynaric started two years ago with the development of a low-earth orbit (LEO) optical terminal for inter-satellite links. The LEO terminal will provide a data rate of 10 Gbps full duplex over distances of up to 4500 km and a compact design with simple mechanical and thermal interfaces to the satellite bus. The Critical Design Review (CDR) shall be held in autumn 2018 and completion of the qualification is planned for 2019. A demonstration mission in LEO using two satellites is planned in 2019/2020. Breadboard testing is in progress for several key components such as the coarse pointing assembly (elevation and azimuth axes), the fine pointing assembly and the communication subsystem. Radiation tests were successfully performed to verify the EEE parts approach using COTS and automotive components. RFI/RFP processes are being done to select key subcontractors/suppliers and to gather costing information for the recurring, high-volume serial production of the terminals. The paper presents the design overview of the terminal and reports on the current development status. The CDR status and results of the breadboard tests are presented and an outlook towards the first demonstration in space is given.

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