- Frequency protection until May - therefore Rocket Lab
- Third pillar of the European GPS alternative
- Four frequency bands for different applications
- Faster to centimetre accuracy
- Not to be confused with Starlink/Iridium PNT
- Response to Baltic Sea disturbances
- Next launches and operational readiness
- TECHNICAL DATA:
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Europe's independence from GPS is being expanded. ESA launches its first Low Earth Orbit Positioning Navigation and Timing (LEO-PNT) mission, which is intended to complement the European GPS alternative Galileo and make it more robust.
Frequency protection until May - therefore Rocket Lab
The time pressure is enormous: Europe must put the allocated L- and S-band frequencies into operation at the International Telecommunication Union (ITU) by May 2026 in order to secure them for the future operational system. "We not only had a development plan to be ready within two years, but also a deadline obligation," explains Roberto Prito, Head of the Celeste programme at ESA.
Hence the launch with Rocket Lab instead of a European launcher: the Vega rocket system was fully booked at the required time and other European options were not available. The two satellites IOD-1 (GMV, Spain) and IOD-2 (Thales Alenia Space, France) have been in New Zealand since 20 February and 3 March and are undergoing final tests at the Rocket Lab Māhia Launch Complex.
Third pillar of the European GPS alternative
Celeste will be the third pillar of the European PNT infrastructure: EGNOS provides integrity signals from geostationary orbit for safety-critical applications such as aviation, the GPS alternative Galileo provides autonomous navigation from medium earth orbit with almost 5 billion users worldwide, and Celeste is intended to bring resilience, new services and greater security from low earth orbit. One important aspect is that many users no longer want to rely on GPS. "A few years ago, many said: With four global satellite constellations and over 100 satellites in orbit, we can use them all," explains Prito. "Today, many users don't want to rely on foreign systems." Celeste supports the sovereignty of the European GPS alternative.
Four frequency bands for different applications
The eleven planned satellites operate in four different frequency bands with specific applications:
- L-band: Supplementing the 5 billion existing Galileo users with additional signals and higher performance.
- S-Band: Integration with 5G/6G mobile chipsets in smartphones - power-saving navigation, as the telecoms chips are also used.
- C-Band: Particularly resistant to jamming and spoofing as well as ionospheric interference - for professional applications such as transport, critical infrastructure and autonomous vehicles
- UHF: Navigation in buildings and under bridges - where signals from today's GNSS systems cannot reach
"We are closer to the user, can send stronger signals and utilise frequencies that would be very complex from MEO," explains Prito. The lower altitude also enables autonomous orbit determination without dependence on ground station infrastructure.
Faster to centimetre accuracy
Celeste does not aim to improve the accuracy of the GPS alternative Galileo - which is already in the centimetre range, and even in the millimetre range for geodetic applications. Instead, the aim is to achieve high accuracy more quickly. "The dynamics of the LEO satellites can help to achieve high accuracy in a much shorter time," explains Prito. The time-to-first-fix - the time until the first position is determined - is also significantly reduced.
In addition, new services are planned that are not possible from MEO: Search-and-rescue for smartphone users (independent of other networks), two-way communication for emergencies, special timing services.
Not to be confused with Starlink/Iridium PNT
When asked about competition from Starlink or Iridium, Benedicto clarifies: "We have to be careful not to compare apples with apples. These systems use existing telecoms signals to calculate a position - these are 'signals of opportunity'." Although these bring resilience through complete independence, they do not aim for the same performance as the European GPS alternative Galileo or Celeste. "They are important, but different in terms of solution and target service."
Response to Baltic Sea disturbances
In 2025, the Swedish Maritime Administration issued several warnings about widespread GPS interference in the Baltic Sea. LEO-PNT with stronger signals and several frequency bands is intended to increase the resilience of the European GPS alternative. ESA tests in Norway (Jammer test) revealed two threats: Jamming Overwhelms receivers with interference signals, Spoofing sends fake signals - even more dangerous because false positions are displayed without the user realising it.
The C-band shows particularly strong resistance to both types of interference as well as to natural ionospheric effects. This could bring considerable safety improvements for sailors in the Baltic Sea in the medium term - independently of GPS.
Next launches and operational readiness
The eight additional satellites (Pathfinder B) are scheduled for launch in mid to late 2027. The "In-Orbit Preparatory Phase" was already approved at the ESA Ministerial Council Conference in November 2025. This phase is no longer just aimed at demonstration, but at preparing and validating an operational system. It remains to be seen when the services will be available for recreational shipping - the test and demonstration period will initially run until 2027, with up to 300 satellites in orbit by 2035.
TECHNICAL DATA:
Celeste LEO-PNT Mission:
- Constellation: 11 satellites (2 Pathfinder A + 9 Pathfinder B)
- Orbital altitude: 510 km (first two), 560 km (further nine)
- Start IOD-1 & IOD-2: 24 March 2026 (at the earliest)
- Launch location: Rocket Lab Māhia Launch Complex, New Zealand
- Launch vehicle: Rocket Lab Electron
- Complete constellation: mid to end of 2035
New services to be offered by Celeste:
- Search-and-Rescue for smartphones (network-independent)
- Two-way emergency communication
- Timing services (only possible from LEO)
- Faster time-to-first-fix
- Faster centimetre accuracy (not more accurate, but faster)
Galileo: Europe's GPS alternative
- Almost 5 billion users worldwide
- Centimetre accuracy (millimetres for geodesy)
- 23,222 km orbital altitude (MEO)
- Triple frequency since launch
- Operational since 2016
MORE ARTICLES ON THE TOPIC:
- Navigation: GPS interference in the Baltic Sea - Swedish Maritime Administration warns
- Navigation: Satellite-independent backup system for the Baltic Sea - R-Mode is being expanded
- Navigation: New GPS disturbances in the Baltic Sea
- Navigation: Galileo goes live - the wait is over
- Navigation: GPS waypoint navigation - tips, tricks and typical mistakes
- Navigation: Astronavigation - only with sextant instead of satellite
Hauke Schmidt
Test & Technology editor
