mercredi 18 janvier 2017

Galileo: Swiss components have broken down

ESA - GALILEO Programme logo.

Jan. 18, 2017

New glitch for the "European GPS": several of the atomic clocks on board its satellites no longer work.

"This does not affect for the moment" the navigation system that has just started its services, according to the European Space Agency (ESA). "This is a sensitive issue", as atomic clocks are "very important" elements for the smooth operation of the satellite navigation system, which is a competitor to the US GPS, ESA Director General Jan Woerner said, A press conference in Paris.

Galileo satellites

However, in his view, we can not speak of "a new setback" for Galileo, which has experienced many delays and problems since the launch of the program in 1999. Its total cost is about ten billion euros .

So far 18 satellites have been launched. The constellation must count 30 operational satellites and two reserve ones by 2020. "The system is not questioned, not at all", Galileo "continues" but "we want to be transparent," said the official.

Four on each satellite

The atomic clocks of Galileo are supposed to ensure to the European system a very high precision. That is why each satellite carefully carries with it four atomic clocks of two types ("passive hydrogen masers" and rubidium atomic clocks). In order for each satellite to work well on this plane, at least one of the four clocks must be in good working order.

Passive hydrogen masers (atomic clock) by Argotec

Currently 9 out of 72 clocks are down (6 passive hydrogen masers, 3 rubidium atomic clocks), said Woerner, pointing out that "on every satellite there are at least two clocks that work."

"To date, thanks to this redundancy of clocks, none of the satellites in the constellation is out of order," he said.

Swiss Clocks

ESA is investigating the causes of the problem and has successfully restarted one of these clocks when previously it thought to have ten broken down. The satellites concerned have been launched at various times and the last ones, in orbit since November, are also concerned.

"We must learn the behavior of these atomic clocks and how to use them," Woerner said. They are manufactured by SpectraTime, based in Neuchâtel, with partners. SpectraTime confirmed to the ats that its experts are involved in research to identify the causes of the outage.

Rubidium atomic clock by SpectraTime

In this context, should the launch of four new Galileo satellites be delayed by an Ariane 5 rocket planned for the second half of 2017? "It's a sensitive issue," said Woerner. "If we wait and have other failures, we risk reducing the capacity of the system. But if we launch new satellites, they risk taking atomic clocks with problems. "

Do not delay the program

"Personally, I am in favor of not delaying the deployment of the constellation," he added. On 15 December, Europe launched the first services of its Galileo system, with the promise of a more precise location, reserved at present for the few possessors of compatible equipment.

Only a handful of privileged, possessors of the few smartphones compatible with Galileo (the first, the Aquaris X5 Plus of the Spanish manufacturer BQ, has been on the market since the autumn) can for now pick up the new signal.

These pioneers will be able to use the European system free of charge to find a pharmacy, the best route to go on holiday or settle their stride in the marathon. But for a mass arrival of products compatible with Galileo, we will have to be a little patient.

To the nearest centimeter

The European service aims to be more efficient with, in particular, a positioning of a precision, of the order of one meter, greater than that of its competitors. In addition, a paid service will allow a location within a few centimeters.

Galileo constellation

Moreover, the European signal will be dated to a few billionths of a second, a useful service for banks, insurance companies and energy suppliers.

Passive hydrogen masers must precisely ensure a stability of the nanosecond (one billionth of a second) per 24 hours, which is equivalent to losing or gaining a second every 2.7 million years. Rubidium clocks offer an accuracy of 10 nanoseconds per day.

As Galileo is compatible with GPS, the user can access both systems simultaneously and improve the quality and reliability of his position.

What is Galileo?:

ESA GALILEO / Navigation:



Images, Text, Credits: ATS/ESA/Argotec/SpectraTime/ Aerospace/Roland Berga.

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