The European Optical Nucleus Network

Kurzfassung

As terrestrial data transmission capacity has been growing quickly, spacecraft to Earth data-rates also need to increase to enable new applications. While K-band (26 GHz) payload data links become a commodity offering multiple Gbps data rates for future Earth Observation missions from Low Earth Orbit, e.g. for the Copernicus program, increasingly stakeholders are looking into optical solutions for spacecraft to ground data links with the expectation of 10 Gbps and multiples thereof. However, the development of optical communications from space to ground has been slow due to the lack of an operational and reliable ground segment that can receive data at multiple locations, mitigating the link blockage by clouds, integrate it in the cloud and make it available to the end user in near real-time. All this within a competitive cost level compared to traditional radio frequency (RF) services. The European Optical Nucleus Network is an initiative between Space Agencies and industry to over-come the lack of availability of an optical ground station network. This is achieved by creating a multi-site, multi-mission network which supports common CCSDS standards and space-terminal implementations available to spacecraft operators with optical communication systems onboard. The idea is that participating parties contribute operations time on self-funded optical ground stations to an integrated ground station network that is made available to the space community as a service. The initial European Optical Nucleus Network consists of optical ground stations from ESA-OPS on Tenerife (Canary Islands), DLR-GSOC in Almeria (Spain) and KSAT in Nemea (Greece). These will be connected to the KSAT network operations center (NOC) in Tromsø that also controls KSAT’s 200 RF-antennas on 22 sites around the globe. From a user perspective this allows a single point of contact and frees the user from managing multiple sites and integrating these through different interfaces. The European Optical Nucleus Network will be the first operational ground station service of its kind made available to the market. Challenges in establishing these initial stations have been multiple. A lack of standards has meant that technologies like multi-mission modems, beacon lasers and optical detectors have not been available off-the-shelf and proprietary solutions become cost drivers. The ground station design, while different for each Nucleus station, focuses on using commercial-off the-shelf components, where available, to build stations that are cost compatible to radio frequency solutions, e.g. by using low cost but observatory-grade telescopes. Also, robotization of operations is essential. During 2021 the first three Nucleus stations will be installed and connected to the Tromsø NOC. Focus will be on gathering operational experience to guarantee a stable service that can compete with traditional RF operations. The DLR/Tesat PIXL-1 mission will be used for testing the network using first operational concepts, and the first customer will be the TOSIRIS 10 Gbps laser-terminal onboard the Bartolomeo platform on the International Space Station in 2022. Once the market develops the network can quickly be expanded globally based on the experience gathered from earlier stages. Besides for LEO missions, the Nucleus network is also planned to be tested for Lunar missions, as optical technology enables data communication that is more cost efficient than traditional RF solutions. This is since optical solutions allow a significant reduction of the necessary transmit and receive aperture diameter for the same or even higher data-rates as the laser signal has a more focused footprint.