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ESA |
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The 600-kilogram Giove-A was launched in December 2005 from Baikonur in Kazakhstan,
aboard a Russian Soyuz-FG rocket |
Galileo gets off the launchpad
Europe’s new satellite radionavigation system
How can you find out exactly where you are on the planet? How can you
best track the movement of an aeroplane? Nowadays, global navigation satellite systems
are likely to provide the answer, with their myriad applications. Two such systems
exist at present: the US Global Positioning System (GPS) and Russia’s Global Navigation
Satellite System (GLONASS). These will soon be joined by Galileo, a new European
system that is expected to improve positioning accuracy even more.
ESA/ P.Carril |
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Giove-A sent its first signals to Earth in January 2006, as part of its mission
to test critical technologies for the Galileo system |
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Giove-A blazes a trail
Galileo is an initiative of the European Commission and is being developed by
the European Space Agency (ESA) as well as the private sector. On 12 January 2006,
the first signals came from its pilot element, the Giove-A satellite that
was launched into a 23 258-kilometre circular orbit on 28 December 2005. Its name
is an acronym for “Galileo in-orbit validation element,” and its primary mission
is to establish Galileo’s use of the radio frequencies that were allocated to the
system by ITU at the World Radiocommunication Conference in 2000. Giove-A
also has the task of testing technologies that will be crucial for operational Galileo
satellites, including receivers on the ground, and of investigating the radiation
environment of the satellites’ planned orbits.
Giove-B, is scheduled to be launched in the first half of 2006 with more
test equipment on board, including a passive hydrogen-maser atomic clock that is
being built in Switzerland. Eventually, it is planned that 30 satellites will be
deployed in the Galileo system, over three planes in medium Earth orbit. A spare
satellite will be included in each plane, which controllers will be able to move
as a replacement for any that becomes faulty. The system as a whole will offer a
global service that is expected to start in 2010.
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Portrait by Justus Sustermans |
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Galileo Galilei (1564–1642) was one of the first people to turn a telescope
onto the night sky. On 7 January 1610, he discovered four satellites of the planet
Jupiter.
He realized that their frequent eclipses could be used as a “clock” for navigators
that is visible everywhere. Tables were published of the Jovian satellites’ movements
to help determine longitude at sea and on land. The name of “Giove” also celebrates
this connection between Galileo and Jupiter — as well as with the science of global positioning |
Why another system?
The demand for positioning systems has increased tremendously in recent years
and it can be said that new ones are needed to provide the wider array of services
that will be offered to a booming market. Another argument in favour of Galileo
is that it gives users more than one global system upon which to rely. Continuity
of service is an important priority for many users.
ESA/J.Huart |
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Galileo is designed to provide a highly accurate, global positioning service
under civilian control |
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In addition, ESA says that Galileo will offer a highly accurate service. When
signals from its two frequency bands are received, the free-of-charge “open service”
will locate items to within 4 metres; location to within 1 metre is expected under
Galileo’s paid-for “commercial service,” and this could go down as low as 10 centimetres
if ground stations complement the satellite signal. In addition, Galileo has enhanced
reliability through including a signal “integrity message” that immediately tells
the user about any errors. Also, it will be possible to receive Galileo in areas
at extreme latitudes.
How will it be used?
As well as offering an open service and an encrypted commercial one, Galileo
will also provide an encrypted safety-of-life service, to be used by emergency personnel,
security authorities, air traffic controllers, and so on. This is just one area
in which the demand for satellite navigation systems is growing rapidly. Other applications
range widely from monitoring the speed of cars, to gathering geographic data, to
helping find sailors lost at sea.
Consumers are expected to be able to switch back
and forth between the Galileo and GPS systems using the same equipment. This will
often be a mobile phone, and tracking these devices is likely to be a particularly
important use of Galileo. It opens up many possibilities for “location-based services,”
such as telling users how to find the nearest station or restaurant. Emergency calls,
too, will become easier to handle. The European Union estimates that of the 180
million or so distress calls made every year in Europe, about 6 million have a poorer
than required response because of missing information about the caller’s location.
Galileo, in conjunction with complementary satellite services and alongside
the worldwide boom in mobile communications, should make an important
contribution to the spread and improvement of location-based information.
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