Helios, Selene (Hellenic Space Dawn A, B)

Helios, Selene [EMTech]

Helios and Selene are Greek 8U CubeSats developed under the Hellenic Space Dawn (HSD) programme, managed by EMTech Space as part of the Greek Connect/National Satellite Space Programme supported by European Space Agency and Greek national authorities. The satellites are intended to demonstrate Greek-developed space technologies for Earth observation and optical communications, including laser intersatellite and satellite-to-ground links.

The mission is focused on near real-time Earth observation services, enabling users to receive imagery within minutes after acquisition. Applications include ship detection, coastal flood and landslide monitoring, agriculture, forestry, light-pollution studies, cartography, emergency mapping, and urban land-use monitoring. The two-satellite constellation is designed to provide up to five daily passes over Greece per satellite, with image resolutions of approximately 16 m and onboard edge-processing capabilities.

Both spacecraft carry CubeCAT optical communication terminals supplied by AAC Clyde Space. CubeCAT is a compact laser communications terminal designed for CubeSats and small satellites, enabling secure high-speed data transfer between spacecraft and ground stations. The payload supports optical intersatellite links and satellite-to-ground laser communications with downlink speeds of up to 1 Gbit/s. The programme aims to perform extensive in-orbit experiments in CubeSat-based optical communications, an area not previously demonstrated on a global scale using CubeSat platforms.

In addition to the laser communications payload, Helios and Selene carry high-resolution Earth-observation cameras. The satellites also serve as an in-orbit validation platform for Greek-developed space and ground-segment intellectual property while supporting the development of the national space industry and collaboration with the wider European space sector.

The programme involves a consortium of Greek organisations and institutions including Integrated Systems Development, Heron Engineering, Leo Space Photonics, Geosystems Hellas, Aristotle University of Thessaloniki, Hellenic Naval Academy, and National and Kapodistrian University of Athens.