GNSS

Synchronizing Galileo’s satellites with an ensemble of highperformance atomic clocks

Europe’s Galileo is a precise satellite navigation system, providing meter-level accuracy and precise timing. An essential ingredient to ensure this stays the case are the atomic clocks aboard each satellite, delivering pinpoint timekeeping that is maintained to a few billionths of a second. These clocks are called atomic because their “ticks” come from ultra-rapid, ultrastable oscillation of atoms between different energy states. Sustaining this performance demands, in turn, even more accurate clocks down on the ground to keep the satellites synchronized and ensure stability of time and positioning for users.

ESA’s ESTEC technical center in the Netherlands is continously monitoring the “Galileo System Time” at the heart of Europe’s satellite navigation system—on an independent basis from the operational Galileo system itself.

For this, the establishment hosts in its UTC Laboratory an “ensemble” of high-performance atomic clocks that are kept in thermally stabilized cleanroom conditions. This collection of fridge-sized atomic clocks, together with means to measure and compare them, provides stable, accurate timing typically accurate to a billionth of a second, almost ten times better than Galileo System Time. https://phys.org

ICAO Council adopts new dual-frequency multiconstellation standards

The International Civil Aviation Organization (ICAO) council achieved a major milestone this week in the global standardization and rollout of new dual-frequency multiconstellation (DFMC) capabilities for international aviation’s Global Navigation Satellite System (GNSS). DFMC GNSS permits the combined leveraging of dual frequency signals from up to four GNSS constellations simultaneously, including the GPS system, Galileo, GLONASS and BeiDou.

The capability has been enabled through latest advances in aircraft-, satellite-, and ground-based augmentation systems, and will become more prevalent as aircraft become increasingly equipped with DMFC-capable avionics. Currently, global aviation GNSS capabilities rely mainly on just one constellation and one frequency via GPS L1, meaning that the new multi-constellation capability will assure greater system accuracy and redundancy, delivering important air network capacity and safety benefits. www.icao.int