Commercialisation of the Small Optical Ground Stations Focal-Optics Assembly (SOFA Evolution)

Kurzfassung

The microwave spectrum has become a highly limited resource in satellite communications. Consequently, the integration of free-space optical communication (FSOC) offers a flexible and scalable architecture that enables high-rate communication to meet increasing demand for bandwidth and capacity without the need for licensing. This technology is being incorporated into European programs such as IRIS² and HydRON, as well as national initiatives. For future missions (e.g. Earth observation), laser-based space-to-ground connections will complement radio downlinks. This requires an extensive network of receiving stations on Earth, so-called optical ground stations (OGS).

Against this background, we have developed a fully integrated, low-cost instrument to supplement standard telescope optics. The “Small OGS Focal-optics Assembly” (SOFA) transforms astronomical observatories and commercial off-the-shelf (COTS) portable telescopes into optical ground stations. SOFA implements pointing, acquisitioning and tracking functionality using low-resolution machine vision, allowing arcsecond-level accuracy in combination with COTS telescope mounts. Free-space data reception of the laser downlink signal is realised using a large-area avalanche photodiode (APD). The design objective of the SOFA is to ensure compatibility with the most in-demand telescope optics on the market. Depending on the telescope's technical specifications, the only adaptations required are the use of corresponding spacers and correction lenses. All sensors utilise the primary beam path of the telescope optics, eliminating the need for complex co-alignment systems and mitigating associated boresight offsets. Through technology transfer, we are striving to make SOFA, and therefore FSOC, accessible to academic institutions, government agencies, and commercial service providers.