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What is Galileo OSNMA?
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How does Galileo OSNMA work?
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Who benefits from Galileo OSNMA?
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EUSPA’s role
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Facts and figures
What is Galileo OSNMA?
With GNSS interferences on the rise, malicious actors may jam or spoof signals to provide unreliable or even fake positioning information.
- Jamming floods the radio frequencies used by GNSS with interference signals, effectively blocking the reception of legitimate signals and disrupting navigation and timing computation.
- Spoofing sends fake GNSS signals to mislead receivers, potentially redirecting the trajectory of aircraft, ships or drones.
Galileo OSNMA mitigates the spoofing risk by providing Galileo users with the means to verify that the navigation data they receive comes from the system itself and has not been modified in any way.
How does Galileo OSNMA work?
Galileo OSNMA adds a ‘digital signature’ to the Galileo Open Service positioning and timing information broadcast in the signal in space.
Using public keys, an OSNMA-enabled receiver decodes the cryptographic data received from the Galileo satellites and verifies that the navigation data is coming from the Galileo system and not from another source.
Galileo OSNMA also makes Galileo signals unpredictable and difficult to replay, making it more challenging to spoof OSNMA-enabled receivers.
To use OSNMA, receivers need to implement the protocol as described in the public specifications and download the certified public cryptographic material from the GSC and EUSPA websites. Additionally, and to ensure the end-to-end authentication process, an OSNMA-enabled receiver shall implement the requirements and processing steps as specified in the OSNMA receiver guidelines.
Dig deeper:
Galileo OSNMA authenticates data for geolocation information from the Galileo Open Service (I/NAV ephemeris and timing parameters) broadcast on the E1-B signal component. This is done by transmitting authentication-specific data in previously reserved fields of the E1 I/NAV message. By using these fields, OSNMA does not introduce any overhead to the system, thus the OS navigation performance remains untouched.
Who benefits from Galileo OSNMA?
By increasing a receiver’s ability to detect spoofing events, Galileo OSNMA brings an added layer of protection to a wide range of applications:
Agriculture
Rail
Road and automotive
Aviation and drones
Maritime
Space
Emergency management
EUSPA’s role
EUSPA:
- develops and operates the Galileo OSNMA’s infrastructure
- is responsible for the security accreditation of the service
- ensures that the service is delivered with high quality and in alignment with the service commitments as specified in the Service Definition Document (SDD)
- fosters Galileo OSNMA’s adoption across various market segments
Facts and figures
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Galileo is the first GNSS system to offer protection from spoofing attacks to civilian users globally.
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The OSNMA Initial Service was declared operational in July 2025.
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Galileo OSNMA is freely accessible to all users.
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The service works in challenging environments, such as in urban areas or mountain regions, ensuring that users’ needs are fulfilled in standard operating conditions for the target applications.
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OSNMA will evolve in the future to provide authentication of additional data broadcast by Galileo (e.g. F/NAV navigation data) and authentication information for GPS broadcast navigation data (L1 C/A). It will also be complemented by the Galileo Signal Authentication Service (SAS) to provide protection at pseudorange level, hence achieving a Galileo fully authenticated positioning solution.
The highly stable atomic clocks are continuously monitored by a global network of sensor stations; corrections are computed and uploaded periodically during scheduled uplinks to maintain consistency with GST and UTC.
GNSS satellites broadcast signals that include their precise time and positioning information.
A receiver on Earth uses signals from at least four satellites to calculate its exact position and solve clock bias.
The synchronised, precise time is then distributed to various systems.
GNSS relies on ionospheric models from ground-based monitoring.
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What is GNSS timing and synchronisation?
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How does it work?
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Benefits of timing and synchronisation
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Where is it used?
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EUSPA’s role
What is GNSS timing and synchronisation?
The precise atomic clocks in the Galileo system allow delivery of very accurate timing data to users. The time synchronisation information disseminated in the Galileo SiS is referenced to the Galileo System Time (GST). This information allows Galileo users to estimate their local time referenced to the GST realisation.
The navigation message includes additional parameters which enable users to obtain a realisation of the UTC time by applying a correction to the GST as specified in the Galileo OS SIS ICD. These parameters provide a prediction of GST-UTC based on UTC realisations available at different European metrological institutes.
GNSS receivers use these time signals to synchronise their local clocks with nano-second-level precision, enabling the synchronised operation of systems across wide geographical areas.
How does it work?
The highly stable atomic clocks are continuously monitored by a global network of sensor stations; corrections are computed and uploaded periodically during scheduled uplinks to maintain consistency with GST and UTC.
GNSS satellites broadcast signals that include their precise time and positioning information.
A receiver on Earth uses signals from at least four satellites to calculate its exact position and solve clock bias.
The synchronised, precise time is then distributed to various systems.
GNSS relies on ionospheric models from ground-based monitoring.
Benefits of timing and synchronisation
High accuracy
GNSS provides precise timing down to a few nanoseconds, which is essential for time-sensitive applications.
Global standard
GNSS timing and synchronisation enables globally consistent and traceable timestamps.
Redundancy
Using multiple GNSS constellations improves accuracy and availability.
Regulatory compliance
GNSS timing and synchronisation provides legally traceable and validated timestamps.
Operational efficiency
Synchronised GNSS timing reduces event correlation errors, boosts network reliability (e.g., power grids, 5G), and eliminates manual adjustments for seamless operations.
Where is it used?
The availability of accurate and secure timing information is crucial for a range of critical infrastructures, like telecommunication networks, energy distribution grids and financial markets.
Banks use GNSS equipment for time stamping and to log events chronologically.
Individual stock exchange servers apply time stamps to the trades they execute and to the quotes they establish.
Electricity grids depend on the timing and synchronisation provided by GNSS.
GNSS timing and synchronisation are critical for mobile telecommunication networks.
EUSPA’s role
EUSPA supports GNSS timing and synchronisation by ensuring the continuity of services like Galileo and EGNOS.
It also promotes applications that depend on precise timing, supports research into secure synchronisation methods like OSNMA, and engages the user community to ensure services meet timing requirements for critical sectors.
EUSPA is developing the forthcoming Galileo Timing Service (TS) – a free-of-charge service that will provide timing and synchronisation information, including the monitoring of UTC and Global Standard Time (GST) products.
