Tag Archives: GST (Galileo System Time)

GST or Galileo System Time

Time is Everything With GNSS

Time is Everything With GNSSThe recent news of clock failures on both the European Union’s Galileo and IRNSS satellites (Indian Regional Navigation Satellite System) shows that launching and commissioning new satellite navigation constellations is not a simple business. The news, however, does make it worthwhile asking whether clock failures could have any implications for GNSS users — especially professional users such as in the surveying or GIS industries.

The short answer is that satellite clock failures should not directly impact any users of the Galileo or IRNSS satellites. In the event of all clocks (primary and backup) failing on a single GNSS satellite, the satellite becomes unusable. Read more…

Timing service based on Galileo

The timing services supplied by global navigation satellite systems (GNSS) are an increasingly important, but often unrecognised, part of today’s modern infrastructure.

This is because the vital role of space-based timing is only exposed when it fails – something that became abundantly clear in January 2016, when a software upload to US GPS satellites induced a 13-microsecond misalignment.

Although this might seem like a small difference, it had a big impact. Read more…

UTC adjusted by leap second addition

The Coordinated Universal Time (UTC) time standard, based on atomic clocks, is widely used for international timekeeping and as the reference for time in most countries. UTC is the basis of legal time for most of the world.

UTC must be adjusted at irregular intervals to maintain its correlation to mean solar time due to irregularities in the Earth’s rotation. These adjustments, called leap seconds, are pre-determined. Read more…

Orolia, Atomic Clock supplier for FOC Galileo Satellites

Orolia Group, through its subsidiary SpectraTime, has been awarded by a 14.5 million euro contract to supply Rubidium atomic clocks (Rubidium Atomic Frequency Standard, RAFS) and passive hydrogen masers to equip eight FOC Galileo satellites.

Each Galileo satellite carries two Rubidium atomic clocks and a passive hydrogen maser, the most stable clock in the world. Once completed this new contract, in partnership with Astrium and Selex Galileo, will make Spectratime the leading supplier in the world for active atomic clocks in space, including 72 for the Galileo system. Read more…

Galileo Atomic Clocks

An atomic clock works like a conventional clock but the time-base of the clock, instead of being an oscillating mass as in a pendulum clock, is based on the properties of atoms when transitioning between different energy states.

When an atom is excited by an external energy source, it goes to a higher energy state. Then, from this state, it goes to a lower energy state. In this transition, the atom releases energy at a very precise frequency which is characteristic of the type of atom. Read more…

PHM or Passive Hydrogen Maser (1/2)

The Passive Hydrogen Maser (PHM) is the master clock on the Galileo satellite’s payload. Its extremely good performance makes it the most stable of all clocks currently in space, better than 1 nanosecond per day. Some other features: 18 Kg of mass, 28 liters of volume and 20 years lifetime.

The hydrogen maser uses the properties of the hydrogen atom to serve as a precision frequency reference. But, how does it work? Let’s see what is the process: Read more…