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Galileo (satellite navigation)

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Galileo is a global navigation satellite system (GNSS) developed by the European Union. It is managed through the European Space Agency (ESA) and operated by the European Union Agency for the Space Programme (EUSPA).

Praha Holešovice EUSPA vstup 1
Praha Holešovice EUSPA vstup 1

The system is headquartered in Prague, Czechia. Two ground operations centres support the network. One centre is in Oberpfaffenhofen, Germany, which controls the satellites. The other is in Fucino, Italy, which provides essential navigation data. This massive infrastructure allows users to determine their exact position on Earth.

The system works by using a constellation of satellites in space. These satellites transmit signals that contain precise timing and positioning information.

Galileo sat constallation
Galileo sat constallation

A receiver, such as a smartphone or a car navigation tool, picks up these signals.

Galileo in smartphones ESA385423
Galileo in smartphones ESA385423

By calculating the time it takes for signals to arrive from different satellites, the receiver can pinpoint a location. To maintain this extreme precision, the satellites use highly accurate clocks.

ESA Galileo Passive Hydrogen Maser
ESA Galileo Passive Hydrogen Maser

One example is the passive hydrogen maser, which acts as a master clock. Another type is the rubidium atomic clock.

Rb atomic clock Galileo satellite
Rb atomic clock Galileo satellite

These clocks ensure the timing is perfect for accurate measurements.

Galileo offers different levels of service for different users. The Open Service is a basic, lower-precision service that is free and open to everyone. This allows anyone with a compatible receiver to use the system. There is also a high-accuracy service (HAS) that provides Precise Point Positioning data. While this was originally planned as a commercial service, it has been freely available since 24 January 2023.

Galileo satellite model
Galileo satellite model

Additionally, Galileo provides a search and rescue (SAR) function. This is part of the MEOSAR system, which helps locate people in distress.

The history of Galileo is a story of technical and political challenges. The project officially began in May 2003. It is named after the famous Italian astronomer Galileo Galilei. In the early years, the project faced significant funding difficulties. In 2002, a spokesman even stated the project was "almost dead" due to economic issues and pressure from the United States. However, European Union member states decided the system was vital for independence. They wanted a system that could not be turned off by other nations during political conflicts.

Building the constellation required many successful launches over several years. The first experimental satellite, GIOVE-A, launched on 28 December 2005.

Giovea
Giovea

The first operational satellite was launched on 21 October 2011.

Galileo launch on Soyuz, 21 Oct 2011 (6266227357)
Galileo launch on Soyuz, 21 Oct 2011 (6266227357)

By October 2018, the number of active satellites reached 18. As of September 2024, there are 25 launched satellites operating in the constellation. The project has a massive scale, with an estimated cost of €10 billion. The next generation of satellites is expected to begin operating after 2026 to replace the first generation.

One of the most significant aspects of Galileo is its superior accuracy. In certain locations, Galileo has greater horizontal accuracy than the American GPS system. When using broadcast ephemeris, Galileo's accuracy is less than 1 metre, while GPS is about 3 metres.

Galileo Control Centre at the DLR Oberpfaffenhofen site
Galileo Control Centre at the DLR Oberpfaffenhofen site

When using real-time corrections for satellite orbits and clocks, Galileo has a signal-in-space ranging error (SISRE) of only 1.6 cm. In comparison, the GPS SISRE is 2.3 cm. This makes Galileo an incredibly precise tool for scientific and civil applications.

Galileo was also designed to address tensions regarding international security. Initially, the United States expressed concerns that high-precision signals could be used by enemies in military strikes. There was also a concern that the US could not block Galileo signals without interfering with its own GPS.

Galileo - Wolfowitz - Letter
Galileo - Wolfowitz - Letter

To solve this, the European Union reached a compromise to use different frequencies. This allows one system to be blocked or jammed without affecting the other. Today, the two systems can inter-operate. This cooperation allows receivers to use both GPS and Galileo together to create even more accurate navigation results.

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🖼️ Images & Media (13)
File:Praha Holešovice EUSPA vstup 1.jpg
Praha Holešovice EUSPA vstup 1.jpg
File:Galileo - Wolfowitz - Letter.png
Galileo - Wolfowitz - Letter.png
File:Galileo launch on Soyuz, 21 Oct 2011 (6266227357).jpg
Galileo launch on Soyuz, 21 Oct 2011...
File:Galileo sat constallation.gif
Galileo sat constallation.gif
File:Galileo Control Centre at the DLR Oberpfaffenhofen site.jpg
Galileo Control Centre at the DLR...
File:Galileo IOT L-band antenna at Redu ESA219283.jpg
Galileo IOT L-band antenna at Redu ESA219283.jpg
File:ESA Galileo Passive Hydrogen Maser.jpg
ESA Galileo Passive Hydrogen Maser.jpg
File:Rb atomic clock Galileo satellite.jpg
Rb atomic clock Galileo satellite.jpg
File:Galileo on your pocket.jpg
Galileo on your pocket.jpg
File:Giovea.jpg
Giovea.jpg
File:Galileo satellite model.jpg
Galileo satellite model.jpg
File:Galileo in smartphones ESA385423.jpg
Galileo in smartphones ESA385423.jpg

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