GNSS time is an integral part of GNSS services, it becomes unreliable or unavailable when GNSS system outages or signal anomalies occur. Nevertheless, dependency on GNSS for Communication, Navigation and Surveillance (CNS) systems is expected to increase. More and more aircraft are being equipped with systems like ADS-B, SBAS, and GBAS that depend on GNSS being available. For some aircraft classes, GNSS is the only navigation equipment required to fly under Instrument Flight Rules (IFR) and no alternative means of navigation may be available on-board.

Whilst GNSS timing is seen as a key technology for the achievement of high-performance aviation in Europe, other and independent timing sources may be available to backup or complement the GNSS timing and synchronisation service, e.g. atomic clocks, Low Frequency systems, Network Time Protocols (NTPs). Their suitability for usage may depend on various factors, including coverage area, phase of flight and performance requirements of ground equipment for surveillance and communications.

Telespazio UK is the prime contractor responsible for this project and overall technical delivery. This includes responsibility for defining alternative timing concepts and carrying out performance assessments.

Project requirements:

• Assess criticality of the use of GNSS time in aviation
• Define and perform demonstration of innovative timing concepts complementary to GNSS, in order to provide robust and secure timing and synchronisation services for aviation systems and networks
• Provide recommendations to aviation stakeholders (CNS/ATM) to support their progress towards a safer Air Traffic Control