Celeste in-orbit demonstration constellation

The jump from the drawing table to the first launch occurred in under two years, an exceptionally rapid timeline for a satellite‑navigation demonstration mission. Celeste was among the first ESA programmes to follow a New Space‑inspired development approach, enabling faster, more flexible deployment of satellites and technical capabilities, and ensuring Europe remains at the forefront of innovation in satellite navigation.

First satellites

The first leg of the mission is designed around two large CubeSats - a 12U and a 16U - developed respectively by GMV (Spain) and Thales Alenia Space (France).

These two satellites support also an iterative agile New Space development approach for maturing and de-risking technologies and regulatory aspects in preparation of the following more comprehensive satellites.

To be launched in March 2026, these two satellites will serve to validate core technologies and new signals and service capabilities.

Around May 2026, they will bring into use the required frequencies in L- and S-bands signal for the mission’s operational phase, in adherence to International Telecommunication Union regulations, and pave the way for the expansion of the in-orbit demonstration.

Full in-orbit demonstration constellation

Beginning 2027, the mission will be augmented by eight larger satellites with additional capabilities. These new satellites will bring capabilities to other frequency bands like C-band, UHF, and allow two-way functionalities and signal integrity monitoring, as well as multi-satellite service demonstrations.

An additional satellite will test miniaturised atomic clocks on board, along with other technologies, completing the mission’s 11-satellite configuration.

Mission orbit and functions

All satellites in the constellation will operate in a quasi‑polar orbit at an altitude between 500 and 600 km. From this orbit, they will enable a series of critical technology demonstrations, including:

• Autonomous precise orbit determination independent of ground infrastructure.
• Assessment of on-board timing stability and synchronisation performance without atomic clocks.
• Verification of radionavigation service provision in the UHF, L‑, S‑ and C-bands.

In addition, Celeste will offer an in-orbit testbench for a broad range of applications, for autonomous vehicles, railway, maritime and aviation, critical infrastructure, wireless networks, emergency services, and many others.

The Celeste in-orbit demonstration mission is just the stepping stone to Europe’s future LEO navigation capability. Its outcome will help shape the next phase of the Celeste mission - the in-orbit preparatory phase – and inform the deployment of a future European operational navigation system in low Earth orbit.