Galileo TSM Operational Service Definition (OSD) has new updated features.

EUSPA together with the European Commission has published new updates for the Galileo Timing Service Message (TSM) Operational Service Definition (OSD).

GNSS Timing and Synchronisation are crucial to a variety of applications in the current economy, particularly in critical infrastructures. Systems such as 4G/5G mobile networks, banking, and electricity grids demand high-accuracy time and frequency stability across specific geographic areas. Tight synchronisation between distributed nodes is essential for many digital networks, and as transmission speeds increase and spectral efficiency improves with 5G networks, more stringent network stability requirements are expected.

The Galileo Open Service (OS) provides users with free positioning and timing/synchronisation information. Currently, Galileo's timing service is limited to timing determination and dissemination as part of the OS. Recognizing the need to evolve these aspects, a dedicated Timing Service as part of the Galileo Second Generation mission is developed to provide an enhanced service focus on critical infrastructure applications.

Several features are updated for the Timing service:

• TSM Status Flag: A new "TSM Status" flag has been introduced to indicate the status of the TSM. This flag categorizes the TSM into four states: TSM in Test, TSM Operational, and two additional spare states. This classification aims to streamline the understanding and application of the TSM status among users.
• TSM Operational Specification: The TSM OSD now explicitly specifies that it only describes the format and bit allocation applicable to the "TSM Operational" status (TSM Status = 1).
• GST-UTC Status Flag: The previously defined "UTC status" flag has been renamed to "GST-UTC status" flag. This renaming aligns the flag with its specific role in indicating the status of the Galileo System Time (GST) and its conversion to Coordinated Universal Time (UTC).
• Updated Flag Processing Logic: The processing logic for the GST and GST-UTC status flags has been updated to enhance accuracy and reliability.
• Removal of GST-UTC Conversion Parameters: The document no longer includes the GST-UTC conversion parameters and the dedicated Issue of Data (IODUTC).
• Updated Flag Mapping: The mapping between the values of the OS SIS Health flags, GST, and GST-UTC status flags, and supported service levels has been updated. This update ensures a clear correlation between the status flags and the service levels, providing users with an accurate understanding of service availability and quality.

These updates to the Galileo TSM OSD reflect EUSPA's ongoing efforts to enhance the functionality and user experience of the European Union Global Navigation Satellite System (E-GNSS). By continually refining and updating its services, we ensure that the European Union remains at the forefront of global satellite navigation technology.

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