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Galileo (satellite navigation)

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The Galileo positioning system is a proposed satellite navigation system, to be built by the European union as an alternative to the US military-controlled Global Positioning System and the Russian GLONASS. The system should be operational by 2008. It is not abbreviated to GPS. Use of the acronym "GPS", here and elsewhere, refers to the existing United States system.

File:Galileo Satellite System.jpg
27 satellites in orbit. Image: ESA

This system is intended to provide:

  • Greater precision to all users than is currently available.
  • Improved coverage of satellite signals at higher latitudes, which northern regions such as Scandinavia will benefit from.
  • A global positioning system that can be relied upon, even in times of war.

History

The first stage of the Galileo program was agreed upon officially on May 26, 2003 by the European Union and the European Space Agency. But system studies were conducted well before. In 1999 the 4 different concepts (from France, Germany, Italy and The United Kingdom) for Galileo were compared and reduced to one concept by a joint team of engineers from all four countries. The system is intended primarily for civilian use, unlike the US system, which is run by and primarily for the US military. The US reserves the right to limit the signal strength or accuracy of the GPS systems, or to shut down GPS completely, so that non-military users cannot use it in time of conflict. The precision of the signal available to non-military users was limited before 2000 (a process known as selective availability). The European system will not (in theory) be subject to shutdown for military purposes, will provide a significant improvement to the signal available from GPS, and will, upon completion, be available at its full precision to all users, both civil and military.

The European Commission had some difficulty trying to secure funding for the next stage of the Galileo project. European states were wary of investing the necessary funds at a time of economic difficulty, when national budgets were being threatened across Europe. Following the September 11, 2001 Terrorist Attack, The United States Government wrote to the European Union opposing the project, arguing that it would end the ability of the US to shut down GPS in times of military operations. On January 17, 2002 a spokesman for the project sombrely stated that "Galileo is almost dead" as a result of US pressure.

A few months later, however, the situation changed dramatically. Partially in reaction to the pressure exerted by the US Government, European Union member states decided it was important to have their own independent satellite-based positioning and timing infrastructure. All European Union member states became strongly in favour of the Galileo system in late 2002 and, as a result, the project actually became over-funded, which posed a completely new set of problems for the ESA, as a way had to be found to convince the Member States to reduce the funding.

It may be significant to note that on March 20, 2003, the United States and three other countries begin military operations in Iraq, further motivating the EU to develop a navigation system independent of US control.

The European Union and European Space Agency then agreed in March 2002 to fund the project, pending a review in 2003 (which was finalised on May 26, 2003). The starting cost for the period ending in 2005 is estimated at EUR 1.1 billion. The required satellites - the planned number is 30 - will be launched throughout the period 2006-2008 and the system will be up and running and under civilian control from 2008. The final cost is estimated at EUR 3 bn, including the infrastructure on Earth, which is to be constructed in the years 2006 and 2007. At least two thirds of the cost will be invested by private companies and investors, the remaining costs are divided between the European Space Agency and the European Union. An encrypted higher bandwidth Commercial Service with improved accuracy will be available at an extra cost, while the base Open Service will be freely available to anyone with Galileo compatible receiver.

The European Union has agreed to switch to a range of frequencies known as Binary Offset Carrier 1.1 in June 2004, which will allow both European and American forces to block each other's signals in the battlefield without disabling the entire system.

International involvement

In September 2003, China joined the Galileo project. China will invest € 230 million (USD 296 million, GBP 160 million) in the project over the next few years (see external link, below).

In July 2004, Israel signed an agreement with the EU to become a partner in the Galileo project. [1] [2]

On 3 June 2005 the EU and Ukraine initialled an agreement for Ukraine to join the project. EU Press Release.

On September 7 2005 India signed an agreement to take part in the project and to establish a regional augmentation system based on EGNOS.

There is speculation that other countries might join the Galileo project, including Pakistan, Brazil, Mexico, Chile, Japan, Russia, South Korea, Australia, Morocco and Canada. [3] [4]

Political implications of Galileo project

As well as being an impressive technological achievement and a hugely practical tool, Galileo will be a political statement of European independence from the United States and its GPS system. A strong motivator for an independent system is that, though GPS is now widely used worldwide for civilian applications, it is a military system, which as recently as 2000 had selective availability and which can be disabled in times of war. Galileo's proponents argue that civil infrastructure, including aeroplane navigation and landing, should not rely solely upon GPS. It was annouced by President Clinton

System description

Galileo satellites

  • 30 spacecraft
  • orbital altitude: 23222 km (MEO)
  • 3 orbital planes, 56° inclination (9 operational satellites and one active spare per orbital plane)
  • satellite lifetime: >12 years
  • satellite mass: 675 kg
  • satellite body dimensions: 2.7 m x 1.2 m x 1.1 m
  • span of solar arrays: 18.7 m
  • power of solar arrays: 1500 W (end of life)

Services

There will be four different navigation services available:

  • The Open Service (OS) will be free for anyone to access. The OS signals will be broadcast in two bands, at 1164–1214 MHz and at 1563–1591 MHz. Receivers will achieve an accuracy of <4 m horizontally and <8 m vertically if they use both OS bands. Receivers that use only a single band will still achieve <15 m horizontally and <35 m vertically, comparable what the civilian GPS C/A service provides today. It is expected that most future mass market receivers will process both the GPS C/A and the Galileo OS signals, for maximum coverage.
  • The encrypted Commercial Service (CS) will be available for a fee and will offer an accuracy of better than 1 m. The CS can also be complemented by ground stations to bring the accuracy down to less than 10 cm. This signal will be broadcast in three frequency bands, the two used for the OS signals, as well as at 1260–1300 MHz.
  • The encrypted Public Regulated Service (PRS) and Safety of Life Service (SoL) will both provide an accuracy comparable to the Open Service. Their main aim is robustness against jamming and the reliable detection of problems within 10 seconds. They will be targeted at security authorities (police, military, etc.) and safety-critical transport applications (air-traffic control, automated aircraft landing, etc.), respectively.

In addition, the Galileo satellites will be able to detect and report signals from COSPAS-SARSAT search-and-rescue beacons in the 406.0–406.1 MHz band, which makes them a part of the Global Maritime Distress Safety System.

Galileo Satellite Test Beds 2A and 2B

ESA and GJU aim to launch one of the two satellites, GSTB-2A and GSTB-2B, by 6 December 2005. GSTB-2A, built by Surrey Satellite Technology Ltd (SSTL), is basically a transmitter beacon, while GSTB-2B, built by Galileo Industries, has an evolved payload which includes two atomic clocks. In both cases the primary objective is achieving the ITU frequency-filing requirements that require using the allocated transmission frequencies by the set deadline date. GSTB-2B also has clock and MEO environment characterisation objectives, as well as Signal-In-Space and receiver experiments. GSTB-2B will contain a rubidium atomic clock and the first space-qualified passive hydrogen maser atomic clock.

EGNOS

The European geostationary navigation overlay system (EGNOS) is intended to be a precursor to Galileo. EGNOS is a system of satellites and ground stations designed to increase the accuracy of the current GPS and GLONASS in Europe.

Press coverage

References

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