The complete Galileo constellation will comprise satellites spread evenly around three orbital planes at an altitude of 23222 km and inclined at an angle of 56 degrees to the equator. Each satellite will take about 14 hours to orbit the Earth. Two satellites in each plane will be a spare, on stand-by should any operational satellite fail. For more information about orbital parameters, please visit the Orbital and Technical Parameters section.
From most locations, six to eight satellites will always be visible, allowing positions and timing to be determined very accurately to within a few centimetres. Interoperability with the US system of GPS satellites will only increase the reliability of Galileo services.
The first two operational Galileo satellites GSAT0101 and GSAT0102 were launched from Europe's Spaceport in French Guiana in October 2011. The second pair, GSAT0103 and GSAT0104, was launched in October 2012.
Once the In-Orbit Validation (IOV) phase was completed, the remaining satellites are being placed in orbit at regular intervals to reach Full Operational Capability (FOC).
The Galileo IOV satellite
|Mass||about 700 kg|
|Size with solar wings stowed||3.02 x 1.58 x 1.59 m|
|Size with solar wings deployed||2.74 x 14.5 x 1.59 m|
|Design life||more than 12 years|
|Available power||1420 W (sunlight) / 1355 W (eclipse)|
The first pair of Galileo’s FOC phase, GSAT0201 and GSAT0202, was launched in August 2014. Despite having been injected into an incorrect orbit, these were moved to an improved orbit at the end of 2014 and the beginning of 2015.
Subsequent pairs of FOC satellites were launched as follows:
- GSAT0203 and GSAT0204, in March 2015;
- GSAT0205 and GSAT0206, in September 2015;
- GSAT0208 and GSAT0209, in December 2015;
- GSAT0210 and GSAT0211, in May 2016;
- GSAT0207, GSAT0212, GSAT0213 and GSAT0214, in November 2016;
- GSAT0215, GSAT0216, GSAT0217 and GSAT0218, in December 2017.
The Galileo FOC satellites provide the same capabilities as the previous IOV satellites, but with improved performance, such as higher transmit power.
The Galileo FOC satellite
|Mass||about 733 kg|
|Size with solar wings stowed||2.91 x 1.7 x 1.4 m|
|Size with solar wings deployed||2.5 x 1.2 x 1.1 m|
|Design life||more than 12 years|
|Available power||1900 W|
With 22 Galileo satellites in Orbit (4 IOV plus 18 FOC satellites), the constellation is on track to reach completion in 2020.
The pre-Galileo GIOVE (Galileo In-Orbit Validation Element) satellites
The GIOVEs were aimed at testing Galileo positioning system technologies in orbit.
GIOVE-A, was launched in December 2005, its primary goal being to claim the frequencies allocated to Galileo by the International Telecommunications Union (ITU). It has also been used to test the design of two on-board rubidium atomic clocks.
GIOVE-A was the first European satellite to be launched into medium Earth orbit (MEO). It carries two environmental monitors that have been in operation almost continuously since launch, gathering vital data about the Galileo intermediate circular orbit environment and helping in the design of the full constellation.
GIOVE-A was designed and sized for a 27 month mission. Although still operational (by prime contractor Surrey Satellite Technology Ltd of Guildford, UK, to gather radiation data and performance results from a GPS receiver), it was officially retired on 30th June 2012, having been successfully operating for much more than double its design life.
After launch in April 2008, early orbit operations and platform commissioning, GIOVE-B's navigation payload was switched on and signal transmission commenced.
Key facilities in the testing of GIOVE-B signals include the GIOVE-B Control Centre at Telespazio's facilities in Fucino, Italy, the Galileo Processing Centre at ESA's European Space Research and Technology Centre (ESTEC) in the Netherlands, the ESA ground station at Redu, Belgium, and the Rutherford Appleton Laboratory (RAL) Chilbolton Observatory in the United Kingdom.
GIOVE-B was retired from service on 23rd July 2012 after more than 4 years of service, and began raising its orbit to an “graveyard” orbit, where there is no danger of it interfering with the other operational satellites.