Galileo Update

Galileo Update

Oct 2010 | No Comment


Malta foregoes bid to host Galileo

Malta has officially informed the European Commission that it no longer wants to host the headquarters of Galileo, four years after it submitted its official bid. Other member states who were also trying to win this prestigious agency also withdrew their bids, including Italy, France and the UK. There are now only two member states vying for the Galileo Supervisory Authority – Czech Republic and Slovenia.

Navigation satellites contend with stormy Sun

It is a fact that variations in the Sun have effects that extend far out into the Solar System. And the solar activity follows a roughly 11-year ‘sunspot cycle’. That means the next ‘solar maximum’ – solar max for short – is due in 2013, not long after ESA launches its first four operational Galileo satellites. “These Galileo In-Orbit Validation (IOV) satellites will indeed go up during a period of enhanced solar activity,” explains Bertram Arbesser-Rastburg, head of ESA’s Electromagnetics and Space Environment division. “But the solar max is hardly a surprise event. Astronomers counting sunspots have tracked the solar cycle for more than 250 years. All the indications are this solar max will not be especially energetic – the last solar minimum has been unusually long and deep.”

“So it’s reassuring the Galileo satellites won’t be faced with the worst of the worst on day one. But in any case, they have indeed been built to endure the worst of the worst: even then, they would not fail.” The Sun has various potential impacts that satnav system designers must take account of. The first can indeed affect satellites themselves: electromagnetic radiation and charged particles from solar flares can disrupt satellite electronics, induce potentially harmful electrostatic charging and damage onboard materials.

Galileo satellites were designed with precise data on the radiation hazard they faced: in 2005 and 2008 a pair of test satellites, Galileo In Orbit Validation Element (GIOVE) –A and –B, were launched into the constellation’s future orbit. The satellites were fitted with radiation monitors, still returning data to this day.

“Dynamic in nature – especially around where the Sun is shining – the ionosphere may cause noisy scintillations leading to ground receivers losing their satellite locks,” added Arbesser-Rastburg.
“Depending on its local density or ‘total electron count’, the ionosphere can also delay a signal passing through it, amounting to a navigation error on the order of tens of meters.”

Added certainty is given by regional overlay systems: the Wide Area Augmentation System (WAAS) for North America and the European Geostationary Navigation Overlay Service (EGNOS) for Europe, with other systems in development.

“What EGNOS offers is an assurance of integrity for European users of GPS and later Galileo signals,” explained Arbesser-Rastburg. “As well as checking the correctness of satellite orbits and clocks, its pan-European network of ground stations measure small changes in the total electron content of the vertical ionosphere above them to deliver local corrections. This is vital when it comes to planned ‘safety-of-life’ uses such as civil aviation.

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