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The European Space Agency (ESA) has successfully demonstrated the transmission and reception of 5G positioning signals from the Celeste IOD-2 satellite in low Earth orbit, marking a key step toward integrating the worlds of satellite navigation and mobile com…
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ESA / Applications / Satellite navigation / CelesteThe European Space Agency (ESA) has successfully demonstrated the transmission and reception of 5G positioning signals from the Celeste IOD-2 satellite in low Earth orbit, marking a key step toward integrating the worlds of satellite navigation and mobile communications.
On 27 August, the Celeste IOD-2 satellite transmitted 5G positioning signals in S-band that are compliant with the 3rd Generation Partnership Project (3GPP), the international body responsible for mobile telecommunications standards. The signals were successfully received and recorded on the ground and are being analysed to assess their behaviour and performance.
The first two Celeste In-Orbit Demonstration (IOD) satellites were launched in March 2026, with IOD-2 developed under contract led by Thales Alenia Space, and IOD-1 developed under contract led by GMV.
This first-of-its-kind in-orbit demonstration represents an important milestone for positioning using 5G Non-Terrestrial Networks (NTN) and paves the way for future satellite systems capable of delivering both connectivity and positioning services.
“This achievement demonstrates the remarkable capabilities of the Celeste demonstrator satellites and the commitment of the team and all the industrial partners involved. Looking further ahead, combining positioning and connectivity is particularly attractive for Direct-to-Device (D2D) and Internet of Things (IoT) applications. By enabling a single user terminal to support both functions, this approach could accelerate user adoption improve efficiency and enable new services,” says Roberto Prieto-Cerdeira, ESA's Celeste programme manager.
What are Non-Terrestrial Networks?
Non-Terrestrial Networks are communication networks that extend 5G, and soon 6G, mobile connectivity beyond terrestrial infrastructure by using satellites and airborne platforms such as high-altitude balloons and drones.
Today, terrestrial 5G networks already support positioning services of Global Navigation Satellite Systems (GNSS), such as Galileo and GPS, by providing additional corrections which enhance the overall accuracy.
As mobile communications continue to evolve, researchers are investigating how NTN can not only provide connectivity but also become a complementary source of positioning information to traditional GNSS constellations.
Space's part in the 5G revolution
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The demonstration
During the demonstration, the IOD-2 satellite transmitted two representative positioning signals from the broader 3GPP positioning framework for 5G, namely:
- 5G New Radio (NR) Downlink Positioning Reference Signals (DL-PRS) and,
- Narrowband Positioning Reference Signals (NPRS).
The use of standardised, non-proprietary signals is particularly significant as it could enable satellites to communicate directly with mobile phones and low-power IoT devices. Such direct-to-device capabilities would improve interoperability across service providers and allow users to move seamlessly between terrestrial and satellite networks, ensuring continuous coverage from urban centres to remote and underserved regions.
The use of S-band is equally significant as this spectrum is already of interest for satellite communication and direct-to-device services. Demonstrating 3GPP positioning signals in S-band therefore extends positioning capabilities into a frequency domain relevant to future NTN systems, while also providing frequency diversity with respect to L-band GNSS signals.
Taking 5G to the next level
3GPP is currently defining a new set of capabilities for 5G technology, as part of the upcoming Release 21, a packaged release of new features and standards for telecommunications networks.
European industry and international contributors to 3GPP advocate for positioning over NR-NTN and IoT-NTN to be included in 5G during Release 21.
"This experiment shows that we do not need to start from scratch to bring positioning into NTN. We can build on positioning features already developed for terrestrial 5G networks and extend them to satellite systems through targeted adaptations,” explains Florin Grec, ESA’s Celeste Resilient PNT Technical Lead and 3GPP delegate.
“This test is an important step towards demonstrating the feasibility of NTN positioning and gives concrete in-orbit evidence supporting the ongoing 3GPP preparatory work."
What’s next for Celeste?
This achievement is part of Celeste's broader in-orbit experimentation campaign being conducted by ESA together with its industrial partners. Since the first two Celeste IOD satellites transmitted their first navigation signal broadcast in April 2026, they have completed in-orbit commissioning and entered the nominal experimentation and demonstration phase.
Running until late 2026, the campaign is investigating several of the key technologies required for future low Earth orbit positioning, navigation and timing systems. These include onboard orbit determination, time synchronisation, the generation and transmission of navigation signals in both L-band and S-band, as well as experimental waveforms designed to enhance resilience and enable new services. The transmission of 3GPP-based 5G NTN positioning signals in S-band is the most recent test.
“The Celeste IOD-1 and IOD-2 satellites have already achieved the vast majority of their in-orbit objectives, demonstrating the key technologies they were designed to validate and gathering essential data for further analysis. Our next major milestone will be their participation in Jammertest in September, where they will broadcast dedicated signals to support experiments under representative interference conditions,” says Roberto Prieto-Cerdeira, ESA's Celeste programme manager.
More experiments to come and next phase
Beginning with the next Celeste satellites, IOD-3 through IOD-10, which are planned to be launched from second half of 2027 onwards, ESA plans to progress from single-satellite ranging towards multi-satellite positioning. In this approach, positioning signals transmitted by multiple low Earth orbit satellites will be combined to determine a user's location.
These future experiments will enable ESA and the industrial teams led by GMV and Thales Alenia Space to investigate topics such as multi-satellite ranging, frequency diversity, positioning performance, resilient waveform design, coexistence between communications and positioning signals, receiver implementation, and operation under representative direct-to-device conditions.
Beyond the demonstrator, the next step is the Celeste In-Orbit Preparatory phase, currently under procurement, which will focus on qualifying essential technologies, strengthening Europe’s capacity for scalable and cost-effective production, and validating the overall key system concepts in-orbit. This phase will unlock global commercial opportunities and innovation and reinforce Europe's leadership in emerging PNT markets.
The results of the Celeste mission will pave the way for a European multi-layer PNT, preparing European industry and supporting the European Union’s decision for its own operational navigation layer in LEO, complementing Galileo and EGNOS.
About Celeste
The Celeste mission is ESA's initiative for LEO-PNT (Low Earth Orbit Positioning Navigation and Timing) and is currently in its in-orbit demonstration phase. This first phase features a demonstration constellation of 11 satellites that will fly in low Earth orbit to test innovative signals across various frequency bands. Its goal is to advance satellite navigation concepts for resilient positioning, navigation and timing services.
The Celeste In-Orbit Demonstration (IOD) fleet is being developed through two parallel contracts respectively led by GMV (ES) with OHB (DE) as core partner, and by Thales Alenia Space (FR) as prime and Thales Alenia Space (IT) as space segment responsible. The two consortia involve over 50 entities from more than 14 European countries.
The Celeste In-Orbit Preparatory phase will advance European industry's readiness to develop a potential future LEO-PNT operation system for the European Union, adding a new layer to the European PNT ecosystem with Galileo at its core.
Celeste also contributes to one of the three core pillars of ESA’s new European Resilience from Space (ERS) initiative, endorsed at CM25. ERS addresses critical security and resilience needs for Member States while laying the groundwork for future European strategic space capabilities.
For more information, visit www.esa.int/Celeste/.