Galileo (satellite navigation)
|Country/ies of origin||European Union|
|Accuracy||1 metre (public)
1 cm (encrypted)
|Satellites in orbit||14 operational, 2 testing only, 2 unavailable, 2 retired, and 4 commissioning (12/2017)|
|Regime(s)||3x MEO planes|
|Orbital height||23,222 km (14,429 mi)|
Galileo is the global navigation satellite system (GNSS) that is currently being created by the European Union (EU) through the European Space Agency (ESA), headquartered in Prague in the Czech Republic, with two ground operations centres, Oberpfaffenhofen near Munich in Germany and Fucino in Italy. The €5 billion project is named after the Italian astronomer Galileo Galilei. One of the aims of Galileo is to provide an independent high-precision positioning system so European nations do not have to rely on the Russian GLONASS, Chinese BeiDou or US GPS systems, which could be disabled or degraded by their operators at any time. The use of basic (lower-precision) Galileo services will be free and open to everyone. The higher-precision capabilities will be available for paying commercial users. Galileo is intended to provide horizontal and vertical position measurements within 1-metre precision, and better positioning services at higher latitudes than other positioning systems.
Galileo is to provide a new global search and rescue (SAR) function as part of the MEOSAR system. Satellites will be equipped with a transponder which will relay distress signals from emergency beacons to the Rescue coordination centre, which will then initiate a rescue operation. At the same time, the system is projected to provide a signal, the Return Link Message (RLM), to the emergency beacon, informing them that their situation has been detected and help is on the way. This latter feature is new and is considered a major upgrade compared to the existing Cospas-Sarsat system, which does not provide feedback to the user. Tests in February 2014 found that for Galileo's search and rescue function, operating as part of the existing International Cospas-Sarsat Programme, 77% of simulated distress locations can be pinpointed within 2 km, and 95% within 5 km.
The first Galileo test satellite, the GIOVE-A, was launched 28 December 2005, while the first satellite to be part of the operational system was launched on 21 October 2011. As of December 2017, 22 of the planned 30 active satellites are in orbit. The next launch, which will bring the system to operational completion, is planned in mid 2018. Galileo started offering Early Operational Capability (EOC) on 15 December 2016, providing initial services with a weak signal, and is expected to reach Full Operational Capability (FOC) in 2019. The complete 30-satellite Galileo system (24 operational and 6 active spares) is expected by 2020.
- 1 History
- 2 International involvement
- 3 System description
- 4 Constellation
- 5 Applications and impact
- 6 See also
- 7 Notes
- 8 References
- 9 Bibliography
- 10 Further reading
- 11 External links
In 1999, the different concepts of the three main contributors of ESA (Germany, France and Italy) for Galileo were compared and reduced to one by a joint team of engineers from all three countries. The first stage of the Galileo programme was agreed upon officially on 26 May 2003 by the European Union and the European Space Agency. The system is intended primarily for civilian use, unlike the more military-orientated systems of the United States (GPS), Russia (GLONASS), and China (Beidou-1/2, COMPASS). The European system will only be subject to shutdown for military purposes in extreme circumstances (like armed conflict). It will be available at its full precision to both civil and military users. The countries that contribute most to the Galileo Project are Germany and Italy.
The European Commission had some difficulty funding the project's next stage, after several allegedly "per annum" sales projection graphs for the project were exposed in November 2001 as "cumulative" projections which for each year projected included all previous years of sales. The attention that was brought to this multibillion-euro growing error in sales forecasts resulted in a general awareness in the Commission and elsewhere that it was unlikely that the program would yield the return on investment that had previously been suggested to investors and decision-makers.[better source needed] On 17 January 2002, a spokesman for the project stated that, as a result of US pressure and economic difficulties, "Galileo is almost dead."
A few months later, however, the situation changed dramatically. European Union member states decided it was important to have a satellite-based positioning and timing infrastructure that the US could not easily turn off in times of political conflict.
The European Union and the European Space Agency agreed in March 2002 to fund the project, pending a review in 2003 (which was completed on 26 May 2003). The starting cost for the period ending in 2005 is estimated at €1.1 billion. The required satellites (the planned number is 30) were to be launched between 2011 and 2014, with the system up and running and under civilian control from 2019. The final cost is estimated at €3 billion, including the infrastructure on Earth, constructed in 2006 and 2007. The plan was for private companies and investors to invest at least two-thirds of the cost of implementation, with the EU and ESA dividing the remaining cost. The base Open Service is to be available without charge to anyone with a Galileo-compatible receiver, with an encrypted higher-bandwidth improved-precision Commercial Service available at a cost. By early 2011 costs for the project had run 50% over initial estimates.
Tension with the United States
Galileo is intended to be an EU civilian GNSS that allows all users access to it. Initially GPS reserved the highest quality signal for military use, and the signal available for civilian use was intentionally degraded (Selective Availability). This changed with President Bill Clinton signing a policy directive in 1996 to turn off Selective Availability. Since May 2000 the same precision signal has been provided to both civilians and the military.
Since Galileo was designed to provide the highest possible precision (greater than GPS) to anyone, the US was concerned that an enemy could use Galileo signals in military strikes against the US and its allies (some weapons like missiles use GNSSs for guidance). The frequency initially chosen for Galileo would have made it impossible for the US to block the Galileo signals without also interfering with its own GPS signals. The US did not want to lose their GNSS capability with GPS while denying enemies the use of GNSS. Some US officials became especially concerned when Chinese interest in Galileo was reported.
An anonymous EU official claimed that the US officials implied that they might consider shooting down Galileo satellites in the event of a major conflict in which Galileo was used in attacks against American forces. The EU's stance is that Galileo is a neutral technology, available to all countries and everyone. At first, EU officials did not want to change their original plans for Galileo, but have since reached the compromise that Galileo is to use a different frequency. This allowed the blocking or jamming of either GNSS without affecting the other.
GPS and Galileo
One of the reasons given for developing Galileo as an independent system was that position information from GPS can be made significantly inaccurate by the deliberate application of universal Selective Availability (SA) by the US military. GPS is widely used worldwide for civilian applications; Galileo's proponents argued that civil infrastructure, including airplane navigation and landing, should not rely solely upon a system with this vulnerability.
On 2 May 2000, SA was disabled by the President of the United States, Bill Clinton; in late 2001 the entity managing the GPS confirmed that they did not intend to enable selective availability ever again. Though Selective Availability capability still exists, on 19 September 2007 the US Department of Defense announced that newer GPS satellites would not be capable of implementing Selective Availability; the wave of Block IIF satellites launched in 2009, and all subsequent GPS satellites, are stated not to support SA. As old satellites are replaced in the GPS Block IIIA program, SA will cease to be an option. The modernisation programme also contains standardised features that allow GPS III and Galileo systems to inter-operate, allowing receivers to be developed to utilise GPS and Galileo together to create an even more accurate GNSS.
Cooperation with the United States
In June 2004, in a signed agreement with the United States, the European Union agreed to switch to a modulation known as BOC(1,1) (Binary Offset Carrier 1.1) allowing the coexistence of both GPS and Galileo, and the future combined use of both systems.
The European Union also agreed to address the "mutual concerns related to the protection of allied and US national security capabilities."
First experimental satellites: GIOVE-A and GIOVE-B
The first experimental satellite, GIOVE-A, was launched in December 2005 and was followed by a second test satellite, GIOVE-B, launched in April 2008. After successful completion of the In-Orbit Validation (IOV) phase, additional satellites were launched. On 30 November 2007 the 27 EU transport ministers involved reached an agreement that Galileo should be operational by 2013, but later press releases suggest it was delayed to 2014.
Funding again, governance issues
In early 2007 the EU had yet to decide how to pay for the system and the project was said to be "in deep crisis" due to lack of more public funds. German Transport Minister Wolfgang Tiefensee was particularly doubtful about the consortium's ability to end the infighting at a time when only one testbed satellite had been successfully launched.
Although a decision was yet to be reached, on 13 July 2007 EU countries discussed cutting €548m ($755m, £370m) from the union's competitiveness budget for the following year and shifting some of these funds to other parts of the financing pot, a move that could meet part of the cost of the union's Galileo satellite navigation system. European Union research and development projects could be scrapped to overcome a funding shortfall.
In April 2008, the EU transport ministers approved the Galileo Implementation Regulation. This allowed the €3.4bn to be released from the EU's agriculture and administration budgets to allow the issuing of contracts to start construction of the ground station and the satellites.
In June 2009, the European Court of Auditors published a report, pointing out governance issues, substantial delays and budget overruns that led to project stalling in 2007, leading to further delays and failures.
In October 2009, the European Commission cut the number of satellites definitively planned from 28 to 22, with plans to order the remaining six at a later time. It also announced that the first OS, PRS and SoL signal would be available in 2013, and the CS and SOL some time later. The €3.4 billion budget for the 2006–2013 period was considered insufficient. In 2010 the think-tank Open Europe estimated the total cost of Galileo from start to 20 years after completion at €22.2 billion, borne entirely by taxpayers. Under the original estimates made in 2000, this cost would have been €7.7 billion, with €2.6 billion borne by taxpayers and the rest by private investors.
The launch of the first four in-orbit validation (IOV) satellites was planned for the second half of 2011, and the launch of full operational capability (FOC) satellites was planned to start in late 2012.
In March 2010 it was verified that the budget for Galileo would only be available to provide the 4 IOV and 14 FOC satellites by 2014, with no funds then committed to bring the constellation above this 60% capacity. Paul Verhoef, the satellite navigation program manager at the European Commission, indicated that this limited funding would have serious consequences commenting at one point "To give you an idea, that would mean that for three weeks in the year you will not have satellite navigation" in reference to the proposed 18-vehicle constellation.
In July 2010, the European Commission estimated further delays and additional costs of the project to grow up to €1.5-€1.7 billion, and moved the estimated date of completion to 2018. After completion the system will need to be subsidised by governments at €750 million per year. An additional €1.9 billion was planned to be spent bringing the system up to the full complement of 30 satellites (27 operational + 3 active spares).
In January 2011, infrastructure costs up to 2020 were estimated at €5.3 billion. In that same month, Wikileaks revealed that Berry Smutny, the CEO of the German satellite company OHB-System, said that Galileo "is a stupid idea that primarily serves French interests". The BBC understood in 2011 that €500 million (£440M) would become available to make the extra purchase, taking Galileo within a few years from 18 operational satellites to 24.
Twenty-two further satellites with Full Operational Capability (FOC) were on order as of 1.1.2018[update]. The first four pairs of satellites were launched on 22 August 2014, 27 March 2015, 11 September 2015 and 17 December 2015.
In January 2017, news agencies reported that six of the passive hydrogen maser and three of the rubidium atomic clocks had failed. Four of the full operational satellites have each lost at least one clock; but no satellite has lost more than two. The operation of the constellation has not been affected as each satellite is launched with three spare clocks. The possibility of a systematic flaw is being considered. The Swiss producer of both onboard clocktypes SpectraTime declined to comment. According to ESA they concluded with their industrial partners for the rubidium atomic clocks some implemented testing and operational measures were required. Additionally some refurbishment is required for the rubidium atomic clocks that still have to be launched. For the passive hydrogen masers operational measures are being studied to reduce the risk of failure. China and India use the same SpectraTime-built atomic clocks in their satellite navigation systems. ESA has contacted the Indian Space Research Organisation (ISRO) who initially reported not having experienced similar failures. However, at the end of January 2017, Indian news outlets reported that all three clocks aboard the IRNSS-1A satellite (launched in July 2013 with a 10-year life expectancy) had failed and that a replacement satellite would be launched in the second half of 2017. In July 2017 the European Commission reported that the main causes of the malfunctions have been identified and measures have been put in place to reduce the possibility of further malfunctions of the satellites already in space. According to European sources ESA took measures to correct both identified sets of problems by replacing a faulty component that can cause a short circuit in the rubidium clocks and improve the passive hydrogen maser clocks as well on satellites still to be launched. However, in August 2017, ISRO also faced clock failures, and these atomic clocks were said to be supplied by European supplier under a 4-million-euro deal.
As of November 2005, Morocco also joined the programme.
In Mid-2006, the Public-Private Partnership fell apart and the European Commission decided to nationalise Galileo as an EU programme.
In November 2006, China opted instead to upgrade Beidou navigation system, its then-regional satellite navigation system. The decision was due to security concerns and issues with Galileo financing.
On 30 November 2007, the 27 member states of the European Union unanimously agreed to move forward with the project, with plans for bases in Germany and Italy. Spain did not approve during the initial vote, but approved it later that day. This greatly improves the viability of the Galileo project: "The EU's executive had previously said that if agreement was not reached by January 2008, the long-troubled project would essentially be dead."
On 3 April 2009, Norway too joined the programme pledging €68.9 million toward development costs and allowing its companies to bid for the construction contracts. Norway, while not a member of the EU, is a member of ESA.
On 18 December 2013, Switzerland signed a cooperation agreement to fully participate in the program, and retroactively contributed €80 million for the period 2008-2013. As a member of ESA, it already collaborated in the development of the Galileo satellites, contributing the state-of-the-art hydrogen-maser clocks. Switzerland's financial commitment for the period 2014-2020 will be calculated in accordance with the standard formula applied for the Swiss participation in the EU research Framework Programme.
As of 2012, the system is scheduled to reach full operation in 2020 with the following specifications:
- 30 in-orbit spacecraft (24 in full service and 6 spares)
- Orbital altitude: 23,222 km (MEO)
- 3 orbital planes, 56° inclination, ascending nodes separated by 120° longitude (8 operational satellites and 2 active spares per orbital plane)
- Satellite lifetime: >12 years
- Satellite mass: 675 kg
- Satellite body dimensions: 2.7 m × 1.2 m × 1.1 m
- Span of solar arrays: 18.7 m
- Power of solar arrays: 1.5 kW (end of life)
The system's orbit and signal accuracy is controlled by a ground segment consisting of:
- 2 Ground Control Centres, located in Oberpfaffenhofen and Fucino for Satellite and Mission Control
- 5 telemetry, tracking & control (TT&C) stations, located in Kiruna, Kourou, Nouméa, Sainte-Marie, Réunion & Redu
- Several worldwide distributed mission data uplink stations (ULS)
- Several worldwide distributed reference sensor stations (GSS)
- A data dissemination network between all geographically distributed locations
The Galileo system will have five main services:
- Open access navigation
- This will be available without charge for use by anyone with appropriate mass-market equipment; simple timing, and positioning down to 1 metre.
- Commercial navigation (encrypted)
- Accuracy to 1 centimetre and guaranteed service for which service providers will charge fees.
- Safety of life navigation
- Open service; for applications where guaranteed precision is essential. Integrity messages will warn of errors.
- Public regulated navigation (encrypted)
- Continuous availability even if other services are disabled in time of crisis. Government agencies will be main users.
- Search and rescue
- System will pick up distress beacon locations; feasible to send feedback, e.g. confirming help is on its way.
Other secondary services will also be available.
Each Galileo satellite has two master passive hydrogen maser atomic clocks and two secondary rubidium atomic clocks which are independent of one other. As precise and stable space-qualified atomic clocks are critical components to any satellite-navigation system, the employed quadruple redundancy keeps Galileo functioning when onboard atomic clocks fail in space. The onboard passive hydrogen maser clocks' precision is four times better than the onboard rubidium atomic clocks and estimated at 1 second per 3 million years (a timing error of a nanosecond or 1 billionth of a second (10−9 or 1/1,000,000,000 s) translates into a 30 cm (11.8 in) positional error on Earth's surface), and will provide an accurate timing signal to allow a receiver to calculate the time that it takes the signal to reach it. The Galileo satellites are configured to run one hydrogen maser clock in primary mode and a rubidium clock as hot backup. Under normal conditions, the operating hydrogen maser clock produces the reference frequency from which the navigation signal is generated. Should the hydrogen maser encounter any problem, an instantaneous switchover to the rubidium clock would be performed. In case of a failure of the primary hydrogen maser the secondary hydrogen maser could be activated by the ground segment to take over within a period of days as part of the redundant system. A clock monitoring and control unit provides the interface between the four clocks and the navigation signal generator unit (NSU). It passes the signal from the active hydrogen master clock to the NSU and also ensures that the frequencies produced by the master clock and the active spare are in phase, so that the spare can take over instantly should the master clock fail. The NSU information is used to calculate the position of the receiver by trilaterating the difference in received signals from multiple satellites.
The onboard passive hydrogen maser and rubidium clocks are very stable over a few hours. If they were left to run indefinitely, though, their timekeeping would drift, so they need to be synchronized regularly with a network of even more stable ground-based reference clocks. These include active hydrogen maser clocks and clocks based on the caesium frequency standard, which show a far better medium and long-term stability than rubidium or passive hydrogen maser clocks. These clocks on the ground are gathered together within the parallel functioning Precise Timing Facilities in the Fucino and Oberpfaffhofen Galileo Control Centres. The ground based clocks also generate a worldwide time reference called Galileo System Time (GST), the standard for the Galileo system and are routinely compared to the local realizations of UTC, the UTC(k) of the European frequency and time laboratories.
|Satellite launches||Currently in operational orbit
|* One partial launch failure resulting in 2 satellites orbiting in a degraded orbit
(Last update: 13 December 2017)
Galileo satellite test beds: GIOVE
In 2004 the Galileo System Test Bed Version 1 (GSTB-V1) project validated the on-ground algorithms for Orbit Determination and Time Synchronisation (OD&TS). This project, led by ESA and European Satellite Navigation Industries, has provided industry with fundamental knowledge to develop the mission segment of the Galileo positioning system.
- GIOVE-A is the first GIOVE (Galileo In-Orbit Validation Element) test satellite. It was built by Surrey Satellite Technology Ltd (SSTL), and successfully launched on 28 December 2005 by the European Space Agency and the Galileo Joint. Operation of GIOVE-A ensured that Galileo meets the frequency-filing allocation and reservation requirements for the International Telecommunication Union (ITU), a process that was required to be complete by June 2006.
- GIOVE-B, built by Astrium and Thales Alenia Space, has a more advanced payload than GIOVE-A. It was successfully launched on 27 April 2008 at 22:16 UTC (4.16 am Baikonur time) aboard a Soyuz-FG/Fregat rocket provided by Starsem.
A third satellite, GIOVE-A2, was originally planned to be built by SSTL for launch in the second half of 2008. Construction of GIOVE-A2 was terminated due to the successful launch and in-orbit operation of GIOVE-B.
The GIOVE Mission segment operated by European Satellite Navigation Industries used the GIOVE-A/B satellites to provide experimental results based on real data to be used for risk mitigation for the IOV satellites that followed on from the testbeds. ESA organised the global network of ground stations to collect the measurements of GIOVE-A/B with the use of the GETR receivers for further systematic study. GETR receivers are supplied by Septentrio as well as the first Galileo navigation receivers to be used to test the functioning of the system at further stages of its deployment. Signal analysis of GIOVE-A/B data confirmed successful operation of all the Galileo signals with the tracking performance as expected.
In-Orbit Validation (IOV) satellites
These testbed satellites were followed by four IOV Galileo satellites that are much closer to the final Galileo satellite design. The Search & Rescue feature is also installed. The first two satellites were launched on 21 October 2011 from Guiana Space Centre using a Soyuz launcher, the other two on 12 October 2012. This enables key validation tests, since earth-based receivers such as those in cars and phones need to "see" a minimum of four satellites in order to calculate their position in three dimensions. Those 4 IOV Galileo satellites were constructed by Astrium GmbH and Thales Alenia Space. On 12 March 2013, a first fix was performed using those four IOV satellites. Once this In-Orbit Validation (IOV) phase has been completed, the remaining satellites will be installed to reach the Full Operational Capability.
Full Operational Capability (FOC) satellites
On 7 January 2010, it was announced that the contract to build the first 14 FOC satellites was awarded to OHB System and Surrey Satellite Technology Limited (SSTL). Fourteen satellites will be built at a cost of €566M (£510M; $811M). Arianespace will launch the satellites for a cost of €397M (£358M; $569M). The European Commission also announced that the €85 million contract for system support covering industrial services required by ESA for integration and validation of the Galileo system had been awarded to Thales Alenia Space. Thales Alenia Space subcontract performances to Astrium GmbH and security to Thales Communications.
In February 2012, an additional order of eight satellites was awarded to OHB Systems for €250M ($327M), after outbidding EADS Astrium tender offer. Thus bringing the total to 22 FOC satellites.
On 7 May 2014, the first two FOC satellites landed in Guyana for their joint launch planned in summer Originally planned for launch during 2013, problems tooling and establishing the production line for assembly led to a delay of a year in serial production of Galileo satellites. These two satellites (Galileo satellites GSAT-201 and GSAT-202) were launched on 22 August 2014. The names of these satellites are Doresa and Milena named after European children who had previously won a drawing contest. On 23 August 2014, launch service provider Arianespace announced that the flight VS09 experienced anomaly and satellites were injected into an incorrect orbit.
Satellites GSAT-203 and GSAT-204 were launched successfully on 27 March 2015 from Guiana Space Centre using a Soyuz four stage launcher. Using the same Soyuz launcher and launchpad, satellites GSAT-205 (Alba) and GSAT-206 (Oriana) were launched successfully on 11 September 2015.
Starting in November 2016, deployment of the last twelve satellites will use a modified Ariane 5 launcher, named Ariane 5 ES, capable of placing four Galileo satellites into orbit per launch.
On 15 December 2016, Galileo started offering Initial Operational Capability (IOC). The services currently offered are Open Service, Public Regulated Service and Search and Rescue Service.
Second generation (G2G) satellites
As of 2014, ESA and its industry partners have begun studies on Galileo Second Generation satellites, which will be presented to the EC for the late 2020s launch period. One idea is to employ electric propulsion, which would eliminate the need for an upper stage during launch and allow satellites from a single batch to be inserted into more than one orbital plane.
Applications and impact
Science projects using Galileo
In July 2006 an international consortium of universities and research institutions embarked on a study of potential scientific applications of the Galileo constellation. This project, named GEO6, is a broad study oriented to the general scientific community, aiming to define and implement new applications of Galileo.
The GEO6 project aims at fostering possible novel applications within the scientific UC of GNSS signals, and particularly of Galileo.
The AGILE project is an EU-funded project devoted to the study of the technical and commercial aspects of location-based services (LBS). It includes technical analysis of the benefits brought by Galileo (and EGNOS) and studies the hybridisation of Galileo with other positioning technologies (network-based, WLAN, etc.). Within these project, some pilot prototypes were implemented and demonstrated.
On the basis of the potential number of users, potential revenues for Galileo Operating Company or Concessionaire (GOC), international relevance, and level of innovation, a set of Priority Applications (PA) will be selected by the consortium and developed within the time-frame of the same project.
These applications will help to increase and optimise the use of the EGNOS services and the opportunities offered by the Galileo Signal Test-Bed (GSTB-V2) and the Galileo (IOV) phase.
The European Satellite Navigation project was selected as the main motif of a very high-value collectors' coin: the Austrian European Satellite Navigation commemorative coin, minted on 1 March 2006. The coin has a silver ring and gold-brown niobium "pill". In the reverse, the niobium portion depicts navigation satellites orbiting the Earth. The ring shows different modes of transport, for which satellite navigation was developed: an airplane, a car, a lorry, a train and a container ship.
A number of devices are compatible with Galileo. Samsung Galaxy S8, Moto X4, Apple iPhone 8 and iPhone X smartphones are compatible with Galileo, the first mainstream smartphones advertised with this capability.
- Binary Offset Carrier modulation – the modulation family used in Galileo
- Commercialization of space
- European Geostationary Navigation Overlay Service
- Multiplexed binary offset carrier modulation - the modulation type chosen for Galileo Open Service signals and modernized GPS signals
- Orbital periods and speeds are calculated using the relations 4π²R³ = T²GM and V²R = GM, where R = radius of orbit in metres, T = orbital period in seconds, V = orbital speed in m/s, G = gravitational constant ≈ 6.673×10−11 Nm²/kg², M = mass of Earth ≈ 5.98×1024 kg.
- Approximately 8.6 times (in radius and length) when the moon is nearest (363 104 km ÷ 42 164 km) to 9.6 times when the moon is farthest (405 696 km ÷ 42 164 km).
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|Wikimedia Commons has media related to Galileo (satellite navigation).|
- Official website
- Galileo ESA website
- European GNSS Supervisory Authority (GSA) – Europa
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- Galileo 12 Real Time Tracking
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