Hydron – The fibre of the sky
Imagine sending massive amounts of data across the globe in seconds, not through cables or crowded radio frequencies, but with lasers connecting satellites and ground stations. This is the vision behind Hydron, the high throughput digital and optical network, led by the European Space Agency (ESA). Hydron aims to establish a fully optical satellite communications network that will transform how data moves through space and back to Earth.
Hydron is ESA’s initiative to build a high-performance optical communications network in multiple orbits for future applications like 6G connectivity from space or resilience missions integrated seamlessly with terrestrial fibre-based implementations.
More secure and faster communications
Modern satellites collect more data than they can currently transmit using radio frequencies alone because the maximum physical limit of using radio waves has been reached. Hydron addresses this issue by complementing radio frequencies with optical links.
Optical links use tightly focused laser beams to achieve connection between two points over long distances. These beams are the size of a grain of sand, which means they must be extremely precisely pointed to the receiving end. Consequently, this communication method ensures more secure data transfer, as it helps avoid interceptors and steer clear of interference, compared to using traditional radio frequencies.
Optical communications also transmit more data per second; they can reach trillions of bits every second. Because laser beams are so efficient, satellite networks can now operate at a level comparable to terrestrial fibre or 5G networks. This enables seamless integration between satellite and ground-based systems, keeping satellite networks aligned with the latest standards in terrestrial connectivity.
This telecommunications network will support applications such as Earth observation, environmental monitoring, commercial services and emergency response by helping free up the crowded radio-frequency spectrum. For example, for Earth observation missions, this hybrid network could mean no longer having to wait for satellites to pass over specific ground stations. Instead, satellites could connect to the network and send data more quickly to other users in the network via laser links when immediate data delivery is not required. This would mean that radio frequencies can be used by more time-sensitive uses, like emergency responders in remote areas.
Why Hydron matters
The demand for bandwidth is rising sharply. By 2030, the satcom market is projected to grow between 60% and 80%, while the cost per bit will continue to drop significantly. Meeting the demand of a data hungry world requires a flexible, scalable network, namely one that mirrors the efficiency of ground systems. Hydron’s architecture, which includes laser links between satellites in various orbits around Earth and optical ground terminals, is built to deliver that flexibility.
Hydron also positions Europe and Canada as a leader in next-generation telecommunications. The project brings together expertise from across the continent s, with contributions from Kepler Communications, Thales Alenia Space, Tesat-Spacecom, Mynaric, the German Space Agency (DLR), Airbus Netherlands, Officina Stellare, Telespazio, and others.
Hydron will comprise a fully optical network of high-capacity optical inter-satellite links and optical ground-satellite links which interconnect space assets with each other and with ground networks, and seamlessly extend terrestrial optical transport networks into space.
The world's first all-optical satetllite communications network
Hydron will begin its implementation through a demonstration system. It is constituted by different parts that complement each other, making up a network across multiple orbits. The first part, a ring of satellites developed by Kepler Communications planned to be launched in 2027, will implement a low Earth orbit (LEO) optical communication segment with the ability to link directly to ground stations.
The second part will turn this ring of satellites into a bigger network by expanding to a higher orbit. To achieve this, two satellites will be added: one in LEO and one in a higher orbit, with the first linking to the second to demonstrate that multi-orbit networks are feasible.
Building the network together with industry
The third part aims to build up the ecosystem. Companies can develop their laser terminal products – in space or on ground – and demonstrate their capabilities directly with the first and second part of Hydron.
The purpose is to engage industry in developing new systems and applications for Hydron. In particular, understanding how sectors such as high-altitude platform stations (e.g., balloons that can serve as artificial satellites), maritime, and aviation could benefit from the envisioned network is a priority.
Establishing networks functional to different companies and uses requires, at the same time, the development of a unified set of technical standards. ESA is coordinating discussions with industry to create such a technical specification, called ESTOL (ESA specification for Terabit Optical Links). Hydron marks a pivotal first step toward this goal, acting as a platform to demonstrate seamless integration between technologies from various companies by implementing ESTOL. By doing so, Hydron aims to set the stage for future optical satellite communications to have clear and agreed upon standards for terabit-per-second optical links.
Looking towards the future, Hydron will evolve to enhance Earth-based applications on the oceans or in the air, as well as future missions to the Moon and beyond. By extending ground fibre networks into orbit and complementing existing radio-frequency systems, ESA is building the principles of a truly global – and interplanetary – communications system, the internet of space.