Benefits of satellite navigation in low Earth orbit
Thanks to its lower orbit, faster dynamics and the introduction of novel signals and new frequencies, satellite constellations for Positioning Navigation Timing in low Earth orbit (LEO-PNT) could augment current GNSS performance, increase its resilience and provide additional services not currently feasible from medium Earth orbit (MEO).
Augmenting Galileo and EGNOS
LEO-PNT allows the broadcasting of stronger signals compared to traditional satellite navigation from MEO, like Galileo, and satellite-based augmentation system in GEO, like EGNOS.
Stronger signals mean an enhanced performance, with better accuracy, availability and robustness, particularly in environments where MEO‑based signals are obstructed or attenuated, like urban settings.
In addition, the lower altitude and rapid motion of LEO satellites introduce greater geometric diversity, which geodetic applications requiring high accuracy, like Precise Point Positioning.
Strengthening resilience
In 2023, the European Commission identified low-Earth-orbit satellite navigation constellations as pivotal to meeting the threat of malicious interference and ensure more robust, diverse, and interference-proof navigation systems.
As ESA’s initiative for satellite navigation in low Earth orbit, Celeste will explore the introduction of new frequency bands into Europe’s PNT ecosystem supposedly more resistant to interference.
Operating at higher frequencies than the traditional L‑band used by Galileo, the C‑band enables the transmission of wider‑bandwidth navigation signals that are inherently more resistant to intentional interference, including jamming and spoofing, as well as naturally occurring disturbances caused by space weather.
Enabling new services
ESA’s Celeste mission will support the emergence of entirely new services enabled by LEO satellite navigation.
Transportation remains one of the most prominent navigation application areas. The first leg of Celeste, the in-orbit demonstrator mission, will offer a testbench for new services for autonomous vehicles, maritime navigation, railway systems and aviation.
Emergency response and public safety could also benefit from satellite navigation from low Earth orbit, vehicles in distress situations could transmit their location directly via satellite, even in the absence of terrestrial connectivity, and exchange low‑bandwidth, safety‑critical messages with emergency services.
In the field of the Internet of Things (IoT), smart cities services and asset-tracking, Celeste will assess how low-power, battery-constrained devices can reliably access positioning signals from low Earth orbit, with the potential of dramatically multiplying the number of connected devices and supporting large-scale IoT deployment.
Celeste also opens the door to two-way navigation service services, using 5G‑compatible waveforms in the S‑band signals following 3GPP 5G Non-Terrestrial Network (NTN). This would help ensure service continuity between terrestrial and non‑terrestrial networks.
Beyond operational services, LEO-PNT would support GNSS-based Earth science. Navigation signals, like the one from Galileo, offer meteorologists and space weather scientists unique ways to observe the atmosphere and the ionosphere. Signals from low Earth orbit would help expand their horizons.