Factfile on Galileo, Europe's rival to GPS

Oct 16, 2011

Following is a snapshot of Europe's Galileo space-based navigation system, the first satellites of which are scheduled to be launched on Thursday from Kourou, French Guiana.

OVERVIEW: Galileo will consist of 30 satellites, six more than the US (GPS). The system will offer several services from 2014, becoming fully operational in 2020 when a of 27 satellites, supported by three spares, is deployed.

Galileo's supporters say the system will be more accurate than the GPS and give Europe independence from the American system, which is run by the US government. Russia's and China's planned Compass systems are also government-run.

HOW IT WORKS: Like GPS, Galileo works by the geometrical process called triangulation. The satellites emit synchronised signals in the 1.1-Gigahertz (GHz) band. Ground receivers capture the signals and compute the time it takes for each signal to arrive from their brief journey across space. Minute differences in time, caused by the varying distances, enable a calculation of the receiver's position on the Earth's surface.

ORBITAL FIX: Galileo satellites will orbit at 23,200 kilometres (14,400 miles) in three orbital planes at a 56-degree angle to the . This disposition helps coverage in cities, where tall buildings can disrupt coverage.

With 27 operational satellites in orbit, there is a greater than 90 percent chance that someone anywhere on the planet -- including the north and south poles -- will be in direct line of at least four satellites.

For most locations, six to eight satellites will be in direct line, making it possible to determine location to within a metre (3.25 feet). The GPS, which became operational in 1995 and is being upgraded, is currently accurate to between three and eight metres (10 and 26 feet).

ATOMIC TIME-KEEPING: Galileo depends on to ensure that is precise. One billionth of a second too fast or too slow translates into an positioning error of about 30 centimetres (12 inches).

The satellites will each contain four timepieces accurate to one second in three million years.

In two hydrogen clocks, hydrogen atoms oscillate between two energy states to generate a signal in the form of an electromagnetic wave. Two compact rubidium clocks use the transition of the rubidium-87 atom between two hyperfine energy states.

ROLLOUT: Two test satellites were launched in 2005 and 2008. The first two operational satellites are scheduled to be hoisted on October 20 by Soyuz, making the Russian rocket's maiden launch from Europe's spacebase.

Two more will follow in 2012, forming the constellation's operational nucleus. Fourteen satellites should be in place by 2015 and able to offer three services, and the rest by 2020. The network will be managed by two control centres in Europe and sensor and uplink stations around the world. The system is designed to be compatible with GPS and Russia's GLONASS.

COST: Initially estimated at 3.4 billion euros, the price tag was hiked by the European Commission earlier this year to 5.4 billion euros (7.2 billion dollars).

Annual operating costs are estimated at 800 million euros for both Galileo and its precursor system, Egnos.

The market for geo-positioning services will grow from 130 billion euros (180 billion dollars) in 2010 to 240 billion euros (330 billion dollars) in 2020, according to the EU executive.

Sources: European Space Agency (ESA), European Commission, US government (GPS.gov)

Explore further: Informing NASA's Asteroid Initiative: A citizen forum

add to favorites email to friend print save as pdf

Related Stories

Two years in space for Galileo satellite

Dec 19, 2007

On 28 December, it will be two years since GIOVE-A - the first Galileo satellite - was launched by a Soyuz rocket from Baikonur, in Kazakhstan. This satellite demonstrates the progress Europe has made in setting ...

Europe defends 'stupid' Galileo satellite

Jan 18, 2011

Europe stood by its much-delayed and over-budget Galileo satellite navigation system on Tuesday despite a rising price tag and a contractor's description of the project as "stupid." ...

Hyper-accurate clocks -- The beating heart of Galileo

May 10, 2007

Travellers have relied on accurate timekeeping for navigation since the development of the marine chronometer in the eighteenth century. Galileo, Europe’s twenty-first century navigation system, also relies ...

Europe Wants To Speed Up Galileo GPS Program

Nov 18, 2005

Former European commissioner Karel Van Miert has been appointed mediator to accelerate Galileo, Europe 's satellite navigation program, said the European Commission on Tuesday.

Recommended for you

Mysteries of space dust revealed

1 hour ago

The first analysis of space dust collected by a special collector onboard NASA's Stardust mission and sent back to Earth for study in 2006 suggests the tiny specks open a door to studying the origins of the ...

A guide to the 2014 Neptune opposition season

6 hours ago

Never seen Neptune? Now is a good time to try, as the outermost ice giant world reaches opposition this weekend at 14:00 Universal Time (UT) or 10:00 AM EDT on Friday, August 29th. This means that the distant ...

Informing NASA's Asteroid Initiative: A citizen forum

Aug 28, 2014

In its history, the Earth has been repeatedly struck by asteroids, large chunks of rock from space that can cause considerable damage in a collision. Can we—or should we—try to protect Earth from potentially ...

Image: Rosetta's comet looms

Aug 28, 2014

Wow! Rosetta is getting ever-closer to its target comet by the day. This navigation camera shot from Aug. 23 shows that the spacecraft is so close to Comet 67P/Churyumov-Gerasimenko that it's difficult to ...

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

wictor
5 / 5 (1) Oct 16, 2011
I am wondering if a receiver using both signals from Galileo and GPS would be able to determine its position with even higher accuracy.
tkjtkj
not rated yet Oct 17, 2011
For most locations, six to eight satellites will be in direct line, making it possible to determine location to within a metre (3.25 feet). The GPS, which became operational in 1995 and is being upgraded, is currently accurate to between three and eight metres (10 and 26 feet)"


Present GPS (controlled by usa government) is accurate to a distance of 1-2 cm. The government artificially limits this capability to the public for political reasons.
kaasinees
not rated yet Oct 17, 2011
For most locations, six to eight satellites will be in direct line, making it possible to determine location to within a metre (3.25 feet). The GPS, which became operational in 1995 and is being upgraded, is currently accurate to between three and eight metres (10 and 26 feet)"


Present GPS (controlled by usa government) is accurate to a distance of 1-2 cm. The government artificially limits this capability to the public for political reasons.


Not political reasons, military reasons. Theres even an off switch for the civilian signal.
tkjtkj
5 / 5 (1) Oct 17, 2011

Not political reasons, military reasons. Theres even an off switch for the civilian signal.


We mean the same: but since when is 'military' not 'political'???
The distinction really escapes me ;)