Minimize Galileo navigation program FOC

Galileo navigation program: FOC (Full Operational Capability)

Spacecraft     Launch    Mission Status     Navigation Payload    SAR/Galileo Payload    Ground Segment


Galileo is a joint initiative of the European Commission (EC) and the European Space Agency (ESA). Galileo will be Europe's own global navigation satellite system, providing a highly accurate, guaranteed global positioning service under civilian control. It will be inter-operable with GPS and GLONASS, the two other GNSS (Global Navigation Satellite Systems). The complete system consists of:

• A space segment of 30 MEO satellites in 3 planes inclined at 56º

• A launch segment to place the satellites into their operational orbits

• A control ground segment for monitoring and control of the satellites

• A mission ground segment managing all mission specific data

• A user ground segment of equipment capable of receiving and using Galileo signals


Figure 1: The Galileo constellation of 30 spacecraft (image credit: ESA)

The Galileo program has been structured into two phases:

1) IOV (In-Orbit Validation) phase: IOV consists of tests and the operation of four satellites and their related ground infrastructure. The first two IOV satellites were launched on Oct. 21, 2011. The second pair of IOV satellites, IOV-3 and IOV-4, were launched on Oct. 12, 2012.

2) FOC (Full Operational Capability) phase: FOC consists of the deployment of the remaining ground and space infrastructure. It includes an initial operational capability phase of 18 operational satellites. The full system will consist of 30 satellites, control centers located in Europe and a network of sensor stations and uplink stations installed around the globe.

On July 1, 2008, the EC and ESA launched the procurement process of Galileo. Political decisions made by the European Parliament and the Council in 2007 resulted in the allocation of a budget for the European satellite navigation programs EGNOS and Galileo and provided for an agreement on the governance structure of the programs.

This framework provides for the deployment of the FOC (Full Operational Capability) of Galileo under a public procurement scheme, entirely financed out of the European Community budget. The European Commission (EC) acts as program manager and contracting authority, and ESA acts as its procurement and design agent.

The procurement initiated includes six WPs (Work Packages). In this setup, ESA functions in its role as the designated procurement agent on behalf of the European Union: 1)

• WP1 deals with system support services.
On January 7, 2010, the EC awarded a contract to TAS-I (Thales Alenia Space-Italia). 2)

• WP2 is dedicated for the ground mission.

• WP3 covers the ground control.

• WP4 covers the development of the spacecraft.
On January 7, 2010, the EC awarded a contract for a first order of 14 satellites to OHB System AG of Bremen, Germany. OHB System teamed with SSTL (Surrey Satellite Technology Ltd.), UK. - Note: In 2012, the OHB-SSTL consortium was awarded a second contract to supply a further 8 spacecraft for the program.

• WP5 deals with the launch services of the constellation.
On January 7, 2010, the EC awarded a contract to Arianespace of France.

• WP6 is dedicated to the preparation activities as well as all the operations services of the fully-deployed Galileo system.

- WP6 Work Order 1 covers all activities related to the completion of the IOV (Galileo In Orbit Validation) activities – the first four Galileo satellites are due for launch in 2011.

- WP6 Work Order 2 is dedicated to the implementation and activities of an integrated engineering team supporting ESA for system operations.

- WP6 Work Order 3 deals with the completion of deployment of operations for Galileo's FOC, scheduled for 2014.

- WP6 Work Order 4 covers the full deployment of the two Galileo Ground Control Centers, in Germany at Oberpfaffenhofen and in Italy at Fucino.
On Oct. 25, 2010, ESA signed a contract with Spaceopal, a joint undertaking between the Italian company Telespazio and the German firm GfR (Gesellschaft für Raumfahrtanwendungen mbH). GfR has been set up by the German Aerospace Center (DLR) to provide operational services for the Galileo system. 3)

Table 1: Overview of the Galileo program Work Packages 1) 2) 3)

Contract kick-off with OHB as the prime of the FOC space segment WP1 (Work Package 1) took place in late January 2010; two years later, again after highly competitive bidding and based on the performance in WP1, OHB was also able win the space segment Work Order 2 contract, thus increasing the total number of satellites to be built to 22. The Galileo FOC project is characterized by an extremely challenging schedule, which foresees a delivery of a finalized satellite every six weeks. 4)




Development of the Galileo Satellites

• June 13, 2022: Every moment of every day, Europe's constellation of Galileo navigation satellites that ring our planet transmits precisely shaped and timed signals, down through the atmosphere, reflecting back from Earth's land, seas and ice and extending far out into space, as far as the Moon. 5)

- This ubiquity is a byproduct of Galileo's goal to provide navigation services to all – but has also led to these signals becoming an important tool for scientific investigation of our environment, atmosphere, weather and even fundamental physics. Leading researchers will gather in Bulgaria this September to discuss the latest scientific uses of Galileo and other satnav systems – and you can register to join them.

- The 8th International Colloquium on the Scientific and Fundamental Aspects of Global Navigation Satellite Systems will take place on 8–16 September in Sofia, Bulgaria, co-organised by ESA and Sofia University St. Kliment Ohridski.

- "Measurement is a fundamental aspect of science, and the signals from Galileo and equivalent GNSS satellites represent an invaluable yardstick to hold against all kind of physical processes," comments Javier Ventura-Traveset, Head of ESA's Navigation Science Office and ESA Chair for this Colloquium.

- "It is well known that fixed GNSS stations are used to monitor geological fault lines and volcanoes, and form the basis of terrestrial reference frames for measuring the precise shape of the Earth. And the occultation of GNSS signals – for instance through ‘rain fade' – helps forecast the weather as well as the structure and trace gas constituents of the atmosphere.


Figure 2: Galileo is Europe's own satellite navigation system, delivering metre-scale accuracy for users and applications across the globe (image credit: EUSPA)


Figure 3: The face of Galileo. Seen here sheathed in multi-layer insulation, the 2.5 m by 1.2 m by 1.1 m satellite's main 1.4-m diameter antenna transmits L-band navigation signals down to Earth. To its left is the hexagonal search and rescue antenna that picks up distress signals and relays them to local emergency services, contributing to the saving of more than 2000 lives annually (image credit: ESA-P. Muller)

- "Reflected GNSS signals are also being employed for altimetry and remote sensing, soon to be tested by ESA's PRETTY satellite, while the timing information embedded within the signals – accurate to a few billionths of a second – can be used for all kinds of scientific testing, including fundamental physics: a pair of Galileo satellites placed in an elliptical orbit delivered the most precise measurement ever of gravitational redshift, how changes in gravity affect the wavelength of light and we have also recently being able to measure orbital perturbations due to Einstein's general relativity."

- "So scientists are eager to go on making increased use of GNSS as a tool for measurement and investigation, which has already gone beyond our initial expectations as we will see with some highly original studies during our Colloquium. ESA's Navigation Science Office aims to support them in this endeavour, coordinating through events such as September's Colloquium. This unique worldwide event is a chance for researchers to share their results and future plans in this area."

- The Colloquium will also discuss in some detail the state of the art of Systems and technologies for navigation in space, such as the use of GNSS beyond terrestrial orbits or the development of dedicated systems for ‘exo-navigation' on the Moon or Mars, as well as their scientific possibilities.


Figure 4: ESA's Moonlight initiative involves expanding satnav coverage and communication links to the Moon. The first stage involves demonstrating the use of current satnav signals around the Moon. This will be achieved with the Lunar Pathfinder satellite in 2024. The main challenge will be overcoming the limited geometry of satnav signals all coming from the same part of the sky, along with the low signal power. To overcome that limitation, the second stage, the core of the Moonlight system, will see dedicated lunar navigation satellites and lunar surface beacons providing additional ranging sources and extended coverage (image credit: ESA, K. Oldenburg)

- This edition will also include ‘transversal' topics of interest to multiple fields, such as GNSS Big Data – compiling and analysing large quantities of satnav signal records – and Internet of Things positioning for science – the placement of tracking sensors on moveable items, floats or animals – as well as the use of GNSS-enabled autonomous vehicles such as drones and High-Altitude Pseudo-Satellites.

- Scientific studies with the potential to improve the future performance of GNSS will also be highlighted, such as tropospheric and ionospheric corrections and ‘hybridisation', looking into adding extra sensors to improve positioning precision and reliability and ‘precise orbit determination' – ways of sharpening the precise knowledge of satellites' position and motion through space.


Figure 5: HAPS (High Altitude Pseudo-Satellites) are platforms that float or fly at high altitude like conventional aircraft but operate more like satellites – except that rather than working from space they can remain in position inside the atmosphere for weeks or even months, variously enabling precise monitoring and surveillance, high-bandwidth communications or back up to existing satellite navigation services (image credit: ESA)

Genesis project

- The potential of GNSS is such that ESA is proposing a dedicated mission called Genesis as part of its Future NAV programme to its Council of Ministers at the end of this year. The Genesis mission will combine, for the first time ever, all space-based ‘geodetic' (or Earth measuring) techniques aboard a single well-calibrated satellite, establishing precise and stable ties between them. Genesis will then become a true dynamic space geodetic observatory allowing to improve the realisation of the Terrestrial Reference Frame (TRF) – the single most precise model of Earth – towards the goal of achieving an accuracy of 1 mm and a long-term stability of 0.1 mm/yr.

- Javier concludes: "The Terrestrial Reference Frame is the foundation for all space- and ground-based observations in Earth Science and Navigation and, therefore, Genesis will have a major significance since it will have an impact on multiple scientific and societal endeavours, from supporting a more accurate monitoring of several climate change essential variables to improve the orbit determination accuracy of all the GNSS satellites, to name two examples."

• June 10, 2022: Ahead of Galileo satellites like this one going to space, they are switched on as if already operating there within ESA's Maxwell EMC Facility. This test procedure is a check of the satellite's ‘electromagnetic compatibility', with all its systems running together to detect any harmful interference between them. 6)

- Once Maxwell's main door is sealed, its metal walls form a ‘Faraday Cage', screening out external electromagnetic signals. The ‘anechoic' foam pyramids covering its interior absorb internal signals – as well as sound – to prevent any reflection, mimicking the infinite void of space for satellite testing.


Figure 6: Seen here sheathed in multi-layer insulation, the 2.5 m by 1.2 m by 1.1 m satellite's main 1.4-m diameter antenna transmits L-band navigation signals down to Earth. To its left is the hexagonal search and rescue antenna that picks up distress signals and relays them to local emergency services, contributing to the saving of more than 2000 lives annually (image credit: ESA-P. Muller)

- To the bottom right of the navigation antenna are a pair of infrared ‘Earth sensors' whose task is to keep the navigation permanently locked onto Earth by homing in on the contrast between the heat of Earth's atmosphere and the cold of deep space. Above them is the laser retro-reflector: lasers are shone up to this from the stations of the International Laser Ranging Service to perform an independent check of the satellite's orbital position down to an accuracy of less than a centimetre, as a backup of standard radio ranging.

- Above that is the circular C-band antenna which every 45 minutes or so receives the navigation messages from the Galileo ground segment. These signals incorporate corrections for slight clock errors, orbital drift or satellite malfunctions that user receivers can process as they perform positioning fixes, helping ensure Galileo remains the world's most accurate satellite navigation system, delivering metre-scale positioning to users around the globe.

- What resembles a white baton on the end of the satellite is its S-band antenna, employed to return ‘housekeeping' telemetry data to mission control on Earth and pick up telecommands in turn to operate the satellite platform and payload – as well as performing the ranging used to estimate the satellite's position in space.

- The Maxwell EMC Facility is part of the ESTEC Test Centre in ESA's technical heart in Noordwijk, the Netherlands – Europe's largest satellite testing facility, which has flight-tested all but two of the 28 Galileo satellites already in orbit, and is currently doing the same for the next 10 satellites planned to join the constellation.

About Galileo

- Galileo is currently the world's most precise satellite navigation system, serving more than three billion users around the globe.

- The Full Operational Capability phase of the Galileo programme is managed and funded by the European Union. The European Commission, ESA and EUSPA (the EU Agency for the Space Programme) have signed an agreement by which ESA acts as design authority and system development prime on behalf of the Commission and EUSPA as the exploitation and operation manager of Galileo/EGNOS. "Galileo" is registered as a trademark in the database of the European Union Intellectual Property Office (n° 002742237).

• January 6, 2022: ESA and EUSPA (European Union Agency for the Space Programme) have confirmed that Arianespace will launch eight additional Galileo satellites. 7)

- Arianespace will launch the first two satellites in 2022, leading to the Full Operational Capability of Galileo open service. Then, three successive launches on Ariane 62 in 2023, 2024 and 2025, will finalize the launch of the first generation of Galileo satellites and will increase the constellation resilience.

- These will be the 13th to 16th Galileo missions by Arianespace, which has orbited all satellites in the constellation.

- The European Union Agency for the Space Programme (EUSPA) has chosen Arianespace to launch four new Galileo satellites for Europe's own satellite navigation system. With this order, EUSPA takes over the role of placing launch services contracts for Galileo from ESA, which acted so far in the name and on behalf of the European Commission and will continue to be the technical authority for these launches.

- This order follows European Space Agency's (ESA) order for the launch of four satellites in October 2021, and will complete the deployment of first-generation Galileo satellites.

- These launches will take place from the Guiana Space Center (CSG), Europe's Spaceport in Kourou, French Guiana. After a first launch this year for Galileo, carrying satellites from a previous order, in the first half of 2022, a second Soyuz launch in 2022 will orbit the first two satellites from this latest order. The next three missions will orbit two satellites each on Ariane 62, in 2023, 2024 and 2025.

- "I would like to thank ESA and EUSPA, along with the European Commission for continuing to entrust us with their satellites," said Stéphane Israël, CEO of Arianespace. "We're very proud to once again be helping EU deploy its own global navigation satellite system. This additional order to the service of Galileo once again confirms Arianespace's assigned mission of ensuring reliable access to space for Europe."

- Each of the eight satellites under this order, built by OHB System AG in Bremen, Germany, will weigh less than 730 kg. They will join the 28 Galileo satellites already deployed to date, as well as the two to be orbited in early 2022 from the Guiana Space Center by Arianespace.

• November 25, 2021: Europe's next two Galileo satellites have been attached to the dispenser on which they will ride to orbit, and the launcher fairing that will protect them during the first part of the ascent to orbit has been closed around the pair. 8)

- Their dispenser has the double duty of securing the two satellites safely in place during the lift off and flight, then deploying the satellites into their target orbit.

- The combined satellites plus dispenser were then placed onto their Soyuz Fregat upper stage, which has the job of hauling the pair most of the way up to medium Earth-orbit, before being enclosed in their launch fairing.

- The next step will see this combined ‘upper composite' being taken to the launch site for integration with the other three stages of their Soyuz launcher, after the launcher is installed on the launch pad.

- Bastiaan Willemse, ESA Galileo Full Operational Capability Satellites Manager comments from Europe's spaceport in Kourou, French Guiana: "So far, everything has been going according to plan and we are heading towards the ending of a smooth launch campaign, which started in early October."

- These first of a total of 12, Galileo ‘Batch-3' satellites, manufactured by OHB Systems and their suppliers from all across Europe.

- The pair arrived from ESA's ESTEC Test Centre to the integration facility in French Guiana in early October, kicking off a busy launch campaign, including initial dispenser ‘fit checks', filling with the hydrazine fuel that will be used to maneuver them during their 12 years of working life and finalization of their navigation system generation units and uploading of security keys.

- These satellites will add to the 26-satellite Galileo constellation already in orbit and delivering Initial Services around the globe.


Figure 7: Galileo satellites 27 - 28 attached to their dispenser in preparation for their 2 December 2021 launch (image credit: ESA-CNES-Arianespace Optique Video du CSG - P Baudon)

• October 10, 2021: The latest pair of Galileo satellites have touched down at Europe's Spaceport in French Guiana, ahead of their launch together next month. 9)

- Cocooned safely within environmentally controlled containers, the satellites were carried across the Atlantic aboard an Ilyushin cargo carrier. The satellites left ESA's ESTEC Test Centre in Noordwijk, the Netherlands, on Tuesday morning heading for Liège Airport in Belgium. From here they flew to Cayenne in French Guiana via a stop in Oporto Airport in Portugal, arriving at their final destination on Wednesday evening local time.

- Once unloaded from the aircraft, the satellites were then driven through the tropical dusk to the cleanroom surroundings of the spaceport nearby Kourou, where they could be safely unpacked to begin the satellite launch campaign.

- These two satellites are the first of the last batch of Galileo First Generation satellites, known as ‘Batch 3', made up of 12 satellites in all. They are built by OHB SE in Bremen, Germany, with their navigation and search and rescue payloads contributed by Surrey Satellite Technology Ltd in Guildford in the UK.

- Before being cleared for launch, the satellites have gone through rigorous testing at ESA's ESTEC Test Centre, the largest satellite test facility in Europe – their last stop before flying to South America.

- These two satellites will be launched together aboard a Soyuz launcher from Europe's Spaceport in French Guiana. The launcher incorporates a Fregat upper stage, which will carry them to their planned 23,222 km altitude medium-Earth orbit.

- These satellites will add to the 26-satellite Galileo constellation already in orbit and delivering Initial Services around the globe.


Figure 8: Loading Galileo satellite aboard lorry. Flown from Liège Airport in Belgium on an Ilyushin cargo carrier, Galileo satellites 27-28 touched down in Cayenne – Félix Eboué Airport in the evening of 6 October 2020. The two satellites, each in their own transport container, were placed on lorries and driven to Europe's Spaceport (image credit: ESA, P. Muller)

- Next month's lift-off will be the 11th Galileo launch in 10 years. Two further launches are planned for next year, to allow Galileo to reach Full Operational Capability in its delivery of services, to be followed by the launches of the rest of the Batch 3 satellites which are currently all undergoing pre-flight testing.

- In parallel to Batch 3's completion of Galileo First Generation deployment, the new Galileo Second Generation satellites, featuring enhanced navigation signals and capabilities, are already in development with their deployment expected to begin by 2024.


Figure 9: Galileos 27-28 seen atop their gold-wrapped Fregat upper stage within their Soyuz launcher fairing (image credit: ESA, P. Carril)

• July 19, 2021: The first Galileo Second Generation hardware has begun testing, with test versions of the satellites' navigation payloads undergoing evaluation by Airbus Defence and Space at their Ottobrunn facility in Germany and by Thales Alenia Space at ESA's ESTEC technical centre in the Netherlands. 10)

- These testbed versions of these new navigation payloads designed by the two companies are undergoing testing of their respective navigation antennas to check whether they meet the ambitious performance levels set for the coming generation of Europe's satellite navigation system.

- Known as the GPLTBs (Galileo Payload Testbeds), these are development models of the navigation payloads intended for the Galileo Second Generation (G2) satellites.


Figure 10: The GPLTBs are development models of the navigation payloads intended for the Galileo Second Generation (G2) satellites. This is a diagram of the Thales Alenia Space GPLTB, with Airbus Defence and Space producing their own equivalent (image credit: ESA)

- The main difference is that instead of being assembled from space-ready components like an actual satellite payload, the GPLTBs are built up from ‘breadboard' electronic parts placed in test racks, with a proof-of-concept version of a navigation antenna attached.

- "The goal with these test campaigns are to prove their design concept early, and anticipate any technical issues that might arise as early as possible," explains Cédric Magueur, ESA's Payload Manager for the Thales G2 satellites.

- "These campaigns also allow to develop and validate new performance measurements concepts for these new generation of complex navigation payloads," adds Dirk Hannes, ESA's Payload Manager for the Airbus G2 satellites. "This will allow us to optimize the production efficiency of the Flight Model series."

- Cédric adds: "Results from the testing will feed into the up-coming Preliminary Design Review for the new satellites, backing up the analyses by the companies with solid measurements. Such early testing also supports the ambitious timescale for the development and construction of G2 satellites, with the first satellites planned to reach orbit by the middle of this decade."

- Galileo is Europe's civil global satellite navigation constellation, currently the world's most precise satnav system, offering meter-scale accuracy to more than 2 billion users around the globe. There are 26 Galileo satellites in orbit, scheduled to be joined by other 12 satellites starting to be deployed by the end of this year.

- Next will come the first 12 G2 satellites, featuring enhanced navigation signals and fully digital payloads. This new generation will be made up of two independent families of satellites meeting the same performance requirements, produced by Thales Alenia Space in Italy and Airbus Defence and Space in Germany.

- Airbus Defence and Space's GPLTB is currently undergoing radiated testing at the company's Ottobrunn facility, inside a Compact Antenna Test Range (CATR). Meanwhile the Thales Alenia Space GPLTB is about to start testing inside ESTEC's own Hybrid European Radio Frequency and Antenna Test Zone (Hertz) chamber.

- These are metal-walled chambers kept isolated from external radio interference, whose inner walls are studded with foam pyramids to minimize radio frequency signal reflections, mimicking the void of space.

- "Up until now all GPLTB testing has taken place by plugging them into test boards," adds Cédric. "These test campaigns mark the first time that their performances will be confirmed in terms of radiating signals."

- Radio-frequency radiation forming of the navigation signals takes place through a combination of digital processing and interaction with the antenna, so practical radio frequency testing is essential to check the true payload performance.

- Cédric explains: "In our first phase we will perform near-field measurements directly around the antenna to measure all the characteristics of the signal shape, to check it matches previous conductance tests. Then via computation we can derive its far-field performance.

- "In the second test phase the actual far-field measurements will be performed, using another feature of the chambers. Thanks to a pair of specially-shaped paraboloid reflectors, the signal from the testbed can be reshaped as if it has travelled the very long distance that actual Galileo signals need to stretch, all the way from an altitude of 23,222 km down to Earth's surface."

- Dirk comments:"On the Airbus side the methodology is substantially the same, except the far-field measurement are currently being performed, to be followed by the near-field.


Figure 11: Airbus Galileo Second Generation satellites. Galileo Second Generation will be made up of two independent families of satellites meeting the same performance requirements, produced by Thales Alenia Space in Italy and Airbus Defence and Space in Germany (image credit: Airbus Defence and Space)


Figure 12: Thales Galileo Second Generation satellites (image credit: Thales Alenia Space)

• June 3, 2021: Europe's Galileo satellite navigation constellation is set to grow. Later this year the first two out of 12 ‘Batch 3' Galileo satellites will be launched by Soyuz from French Guiana. Their last step on the way to launch is situated beside sand dunes on the Dutch coast: the ESTEC Test Centre, which is Europe's largest satellite test facility. 11)

- All but two of the 26 Galileo satellites already in orbit underwent pre-flight testing at this 3000 m2 environmentally-controlled complex, hosting test equipment to simulate all aspects of spaceflight. The Test Centre is operated and managed by European Test Services for ESA.

- All 12 Batch 3 satellites – functionally similar to the Full Operational Capability satellites already in orbit – are scheduled to come here from OHB in Germany to assess their readiness for space, before heading on to French Guiana.

- The first pair of these satellites were already at ESTEC when the COVID-19 pandemic began last year. Testing was briefly interrupted as the Test Centre was closed, but resumed once safety measures were put in place.

- Testing of this first pair was completed in April, and they are now in storage on site. Two more Galileo satellites have since arrived with another due to join them this month.

- Newly-arrived satellites begin by undergoing a two-week immersion in vacuum and temperature extremes that mimic the conditions it faces in space. This ‘thermal–vacuum' test takes place inside a 4.5 m-diameter stainless steel vacuum chamber called Phenix. An inner box called the ‘thermal tent' has sides that are heated to simulate the Sun's radiation or cooled down by liquid nitrogen to create the chill of Sunless space.

- Another test involves switching on all satellite systems within the Maxwell Test Chamber, which is fitted with shielded walls blocking out all external electrical signals and spiky, radio-absorbing ‘anechoic' material that line the chamber to prevent signal reflections. Kept isolated in this way as though floating in infinite space allows ‘electromagnetic compatibility' testing. Each satellite is switched on to check all its systems can operate together without harmful interference.

- Then, once the satellites' solar wings are fitted, which come from Airbus Netherlands in nearby Leiden, they can undergo ‘mass properties testing'. This involves measuring to check their centre of gravity and mass are aligned within design specifications. The more precisely these are known, the more efficiently each satellite's orientation can be controlled with thruster firings in orbit, potentially elongating its working life by conserving propellant.

- Each satellite also undergoes acoustic testing in the LEAF (Large European Acoustic Facility), effectively the largest sound system in Europe.

- A quartet of noise horns are embedded in one wall of this 11 m-wide, 9 m-deep and 16.4 m-high chamber, generating sound by passing nitrogen gas through the horns, surpassing 140 decibels in all. Accelerometers placed within the satellite checked for potentially hazardous internal vibration during this trial by sound.

- Once each satellite's test campaign is over, they are shipped to Europe's Spaceport in French Guiana and prepared for launch. The two tested spacecraft will leave to Kourou in October, to be launched at the end of the year.

- Summer 2020 saw the start of construction of a new 350 m2 cleanroom for the ESTEC Test Centre. Most of the time the ESTEC Test Centre has several other test items as well as Galileo satellites within its walls simultaneously.

- Complex planning and traffic management are necessary to ensure every project get access to the facility they need at the time they need it. So sufficient room is required to accommodate the different customers and allow their movement between test facilities.


Figure 13: Galileo Batch 3 satellites at OHB in Bremen (image credit: OHB)

May 28, 2021: Acting on behalf of the European Commission, ESA has signed two contracts for an overall amount of €1.47 billion, to design and build the first batch of the second generation of Europe's Galileo navigation satellites. 12)

- Following an intense process of open competition, these contracts have been awarded to Thales Alenia Space (Italy) and Airbus Defence & Space (Germany) to create two independent families of satellites amounting to 12 Galileo Second Generation satellites in total.

- "Galileo is a major success for Europe, and these contracts ensure that it is going to be around for a long time to come," comments Paul Verhoef, ESA Director of Navigation. "The Galileo Second Generation will represent a further step forward with the use of many innovative technologies to guarantee unprecedented precision, robustness and flexibility of the system for the benefit of users worldwide."

- Galileo is Europe's civil global satellite navigation constellation, currently the world's most precise satnav system, offering meter-scale accuracy to more than 2 billion users around the globe. With improved accuracy, the new generation should be able to offer decimeter-scale precision positioning to all.

- These Galileo Second Generation (G2) satellites will revolutionize the Galileo fleet, joining the 26 first generation Galileo satellites in orbit today plus the 12 ‘Batch 3' satellites currently in production and testing. The first launch of these Batch 3 satellites will take place later this year.

- The new G2 satellites will be constructed in a short time scale with their first launch expected in less than four years, allowing them to commence operations in space as soon as possible. The G2 satellites will gradually join the existing constellation, but will be much larger than existing satellites. Using electric propulsion for the first time, and hosting an enhanced navigation antenna, their fully digital payloads are being designed to be easily reconfigured in orbit, enabling them to actively respond to the evolving needs of users with novel signals and services.

- New on-board technologies include electric propulsion to propel the satellites from the orbit in which they will be launched to the final operational orbits, allowing two satellites to be launched at once despite their increased mass. Inter-satellite links between the satellites will let them routinely cross-check their performance and reduce their dependency on the availability of ground installations.

- The satellites will also feature a more powerful navigation antenna, more precise onboard atomic clocks, as well as advanced jamming and spoofing protection mechanisms to safeguard Galileo signals.

- Thanks to G2, it will be possible for navigation devices such as smartphones to acquire the signal faster and access services more quickly upon switching on their devices, with lower power consumption. This will open up new perspectives for many new devices to offer positioning capabilities, a true revolution for emerging self-driving cars, autonomous drones and the whole ‘Internet of things'.

- G2 will also offer enhanced services for search and rescue, including two-way communications to the person in trouble. And a new emergency communications capability will enable authorities to warn users in affected regions of imminent dangers such as tsunamis or earthquakes. Such warnings could be sent anywhere on Earth, independently of telecommunication providers, by using Galileo navigation signals as a one-way messaging service.

- Overall, the G2 satellites will incorporate numerous technology upgrades, developed through EU and ESA research and development programs. But the Galileo G2 system will result from a series of seamless upgrades and changes to the G1 system currently in place, without interruption to any of its services.

- The Galileo system will be operated by the EU Agency for the Space Program, EUSPA, based in Prague. ESA and EUSPA are partnering on the development and operations of Galileo.

- ESA is in charge of the design, development, procurement, qualification of Galileo satellites and the associated ground infrastructure on behalf of the European Union, the system owner.


Figure 14: Galileo Second Generation. Galileo is Europe's civil global satellite navigation constellation, currently the world's most precise satnav system, offering meter-scale accuracy to more than 2 billion users around the globe. With improved accuracy, the new generation should be able to offer decimeter-scale precision positioning to all (image credit: ESA)

• January 20, 2021: Today the EC (European Commission) awarded two contracts for 12 Satellites (6 satellites each) for a total of EUR €1.47 billion, to Thales Alenia Space (Italy) and Airbus Defence & Space (Germany) following an open competition. 13)

- With this, the Commission is initiating the launch of the 2nd Generation of Galileo, the European satellite positioning system. The aim is to keep Galileo ahead of the technological curve compared to global competition and maintaining it as one of the best performing satellite positioning infrastructures in the world while strengthening it as a key asset for Europe's strategic autonomy.

- The first satellites of this second generation will be placed in orbit by the end of 2024. With their new capabilities relying on high innovative technologies (digitally configurable antennas, inter- satellites links, new atomic clocks technologies, use of full electric propulsion systems), these satellites will improve the accuracy of Galileo as well as the robustness and resilience of its signal, which will be key for the upcoming digital decade as well as more security & military usage.


- With the Galileo satellite navigation system, Europe operates a state-of-the-art system in positioning, timing and navigation that is recognized worldwide as the most performant of this kind. In operation since 2016, Galileo provides signal services to 2 billion users around the globe. 26 satellites are currently in orbit, with 2 additional satellites due for launch in Q3 2021.

- In May 2018, the Commission launched the tender procedure to procure a first batch of 12 second-generation satellites through a competitive dialog, with the objective of signing two contracts (double source) of 6 satellites each. The tender procedure was run by the European Space Agency (ESA) by delegation. After 2 months of detailed technical and financial evaluation of the industrial offers, ESA recommended to the Commission to proceed with TAS (Thales Alenia Space) and Airbus Defence & Space that represent the best technical and financial offers. The three industrial bidders were notified yesterday.

• 2010: For the Galileo FOC development phase, OHB System of Bremen, Germany teamed with SSTL (Surrey Satellite Technology Ltd.), UK. Within this team, OHB-System is the prime contractor and is responsible for the development of the 22 spacecraft. SSTL is fully responsible for the satellite payloads. The system level activities will be led by OHB-System, making use of the experience gained by SSTL through its GIOVE-A activities. 14)

ESA is already procuring 4 satellites from Astrium through its IOV (In-Orbit Validation) program which brings the number of operational Galileo satellites now under contract to 18.


Figure 15: Illustration of the Galileo FOC spacecraft (image credit: OHB System)

Spacecraft of the FOC series:

The production of the spacecraft series, with a delivery schedule of each pair of satellites in periods of 3 months, requires an assembly line production technique to meet the time table. This can only be achieved by implementing a modular satellite design.

The FOC satellites, 22 in total, provide the same operational services as their predecessors, but they are built by a new industrial team: OHB in Bremen, Germany build the satellites with Surrey Satellite Technology Ltd in Guildford, UK contributing the navigation payloads.


Figure 16: Galileo FOC solar wing deployment being checked at ESA/ESTEC (image credit: ESA)

Legend to Figure 16: The navigation satellite's pair of 1 m x 5 m solar wings, carrying more than 2500 state-of-the-art gallium arsenide solar cells, will power the satellite during its 12 year working life. 15)

The design of the 22 Galileo FOC satellites is quite different with respect to that of their four Galileo IOV (In-orbit Verification) counterparts. For technical and cost reasons, only half of the units aboard were re-used from IOV. Part of the rationale are also more demanding requirements for FOC compared with IOV, e.g. an increased RF signal output power level, tougher radiation requirements, and harsher launch load requirements to name a few. Hence, qualification on subsystem and system level had to be done from scratch (Ref. 4).

Fulfilment of ESA's FOC satellite requirements was achieved through a simple and robust design, leading to a satellite of ~720 kg with a provided power production of 1.9 kW (end of life), which provides navigation signals in L1, E5, and E6 bands, as well as Search-and-Rescue services. The FOC satellite design is depicted in Figure 17.



Figure 17: Galileo FOC satellite design with "plug-in" propulsion module (image credit: OHB System)

A lot of OHB's development work went into optimizing the design for series production. It was identified that in order to meet the production cadence requirement of six weeks, parallelization of work on each satellite would have to be achieved. As this is very hard to achieve at late stages of integration and testing of a satellite, the focus was put in particular on the early stages of MAIT (Manufacturing, Assembly, Integration, and Testing).

The satellites are integrated in seven modules, depicted also in Figure 18:

• the propulsion module (integrated at the propulsion supplier, Moog Inc.)

• the solar generator module (integrated at the solar generator supplier)

• clock, antenna, and payload core module (integrated at SSTL, OHB's co-prime, responsible for the payload, located in Guildford, UK)

• the center and the platform core modules (integrated at OHB's premises in Bremen, Germany).

Work on these seven modules can be executed independently from each other and in parallel to each other. A good example for that is the propulsion module. While in most satellites, the propulsion system is distributed over the entire spacecraft, the modularity intended for Galileo FOC let OHB designers to mount all the propulsion-related systems on one panel, which can be integrated and replaced also late in the MAIT process (as depicted in Figure 17). The big access panel in the launch dispenser-facing side of the satellite increases the ease of access into the satellite, also at late stages of the assembly.

In the next step of integration after module integration, the seven modules form the platform and the payload (see Figure 2), which also can be treated independently from each other and in parallel to each other (payload at SSTL, platform at OHB). Final integration of payload and platform and system level tests are then also carried out at OHB. Subsequently, the integrated and tested satellites are shipped to ETS (European Test Services) in Noordwijk, The Netherlands, for the environmental test campaigns.

Development work was based on early availability of functional models of the board computers. These were used in subsystem breadboards to facilitate software development with hardware in the loop as early on as possible. Further development work was carried out in two thermal development models that focussed on the two thermally critical areas: firstly, the clock panel, where clock temperature stability was demonstrated, and secondly the area of the travelling wave tubes, where sufficient high dissipation on limited radiator area was validated.

On system level, a flat-sat engineering model was employed to check out inter-subsystem compatibility and interaction. A further payload-only engineering model was employed by SSTL at their premises for payload-level development work.


Figure 18: Illustration of satellite modules (image credit: OHB System)

MAIT (Manufacturing, Assembly, Integration, and Testing): The MAIT approach picks up on the design of the satellite and focuses on the series production and the production cadence as well. The production is based on an island mode, while the check-out equipment and ground support equipment stays in place, it is the satellites that move from station to station. The activities that are executed at a given station are trimmed to give all stations more or less the same stay duration. After that duration, all satellites move forward one station. Primary goal is to keep the flow of satellites going, meaning to avoid "clogging" the production pipeline, as this would have impact on all previous islands, which cannot turn to the next satellite in line, whereas all succeeding islands or stations would "run dry". Hence margin for trouble shouting must be taken into account. For larger issues in the production pipeline, there is a so-called "recovery island" foreseen, which is equipped with all types of ground support equipment which can handle problems that take several days or even weeks to resolve while the rest of the pipeline continues normally.

Spacecraft launch mass

730 kg (including 63 kg of fuel and 30 kg margin)

Spacecraft body size, span

2.5 m x 1.2 m x 1.1 m

Spacecraft span

14.67 m

Overall size at launch

2.91 m 1.70 mx 1.40 m

Spacecraft design life

≥12 years in space, ≥ 5 years ground storage


MEO, r=29800 km, inclination = 56º, 3 orbital planes with RAAN spacing of 120º, at EOL transfer to graveyard orbit

Clock frequency stability

PHM (Passive Hydrogen Maser):<4.5 x 10-14 at 30000 s
RAFS (Rubidium Atomic Frequency Standard): <5.1 x 10-14 at 10000 s

Navigation signal
- Minimum EIRP (EOC)
- Bandwidth

3 bands (E5, E6, L1)
- E5: 32.84 dBW, E6: 33.49 dBW, L1: 35.63 dBW
- E5 : 92.07 MHz, E6: 50.00 MHz, L1: 50.00 MHz

Design approach

Satellite consists of 7 modules, resulting in simple interfaces, enabling parallelized MAIT (Manufacturing, Assembly, Integration and Testing)

Satellite reliability

0.811/12 years (w/o SAR PL)

Failure tolerance

- Full performance maintained after single failure
- Autonomous operation and failure recovery features


TEMIC TSC695 32-bit RISC processor (radiation hardened)
- Processing capability: 14 MIPS

Satellite radiation hardness

MEO compliant

Up- / Downlink

2048 MHz Rx / 2225 MHz Ty (encrypted TMTC)
406 MHz Rx (SAR)
5005 MHz Rx (MISANT)
1191.795 MHz, 1278.75 MHz, 1575.42 MHz Tx (NAV), 1544 MHz Tx (SAR)

Common Security Unit
- S-band security L1
- C-band security mission data
- S-band / C-band security L2
- S-band / C-band security L3
- L-and security

Combines functions for payload and platform
- Encryption/decryption, authentication, anti-replay
- Authentication (COMSEC)
- Encryption/decryption, authentication, anti-replay
- Decryption
- Encrypted navigation signals (NAVSEC)

- Primary voltage
- Average power consumption
- Solar generator
Total power produced
Battery type / capacity

- 50 V, regulated
- 1.75 kW (EOL)
- 2 wings, 2 panels each, triple junction GaAs
- 1.9 W (EOL)
- Li-ion, 3.8 kWh


Aluminum sandwich panel design featuring 3 tillable panels and access panels allow late and easy access


3-axis stabilized
- ≤0.3º pitch/roll, ≤1º yaw
- Fine and coarse sun sensors, gyro, Earth horizon sensors
- Reaction wheels, thrusters, magnetorquers


Slanted N2H4 monopropellant thrusters (2 x 4 nozzles with 1 N thrust each, fully redundant), blowdown pressurization

Table 2: Key parameters of the Galileo spacecraft 16)


Figure 19: The main antenna of the FM2 satellite is being inspected at ESTEC prior to mass property testing in August 2013 (image credit: ESA, Anneke Le Floc'h) 17)


Nominal orbit of the Galileo constellation: The Galileo constellation is composed of a total of 30 MEO (Medium Earth Orbit) satellites, of which 6 are spares (Figure 1). Each satellite will broadcast precise time signals, ephemeris and other data. The Galileo satellite constellation has been optimized to the following nominal constellation specifications:

- Circular orbits (satellite altitude of 23,222 km), orbital inclination of 56°, three equally spaced orbital planes.

- Eight operational satellites, equally spaced in each plane, two spare satellite (also transmitting) in each plane.




Galileo launches

• 20 October 2021: On 21 October 2011, the first pair of Galileo navigation satellites was launched by a Russian-built Soyuz rocket from Europe's Spaceport in French Guiana.

- The introduction of Russia's Soyuz 2 rocket to Europe's Spaceport was a milestone of strategic cooperation in the space transportation sector between Europe and the Russian Federation, and an exciting new opportunity for ESA.

- ESA's Ariane 5 rocket at the Spaceport met all requirements for launching large satellites, while ESA's Vega rocket – still under development at that time – would serve the small satellite market. It was found that the reliable Russian Soyuz would consolidate European access to space for medium-sized satellites, thereby complementing the ESA developed launch vehicles, Ariane 5 and Vega, increasing the flexibility of launch services from Europe's Spaceport.

- Russia's space program, meanwhile, would receive additional income through the launch of satellites and spacecraft from one of the world's most attractive and best-placed launch sites, Europe's Spaceport in French Guiana.

- Europe's Spaceport is located five degrees north of the equator enabling a wide range of missions launched eastwards to northwards. Rockets launched here benefit from the ‘slingshot effect', because of the speed of Earth's rotation when launched eastwards. This substantially improves the performance of the Soyuz rocket for launches from French Guiana compared to launches from the historic Baikonur Cosmodrome.

- In 2003, the ESA Ministerial Council in Paris approved the proposal to operate Soyuz from Europe's Spaceport. Seven Member States participated in the ESA program (Austria, Belgium, France, Germany, Italy, Spain, Switzerland), with further contributions from the European Union and Arianespace . This would cover both construction of the launch complex as well the adaptation of the Soyuz vehicle to enable it to operate from French Guiana.

- In February 2007, construction of a launch site for Soyuz some 13 km northwest of the Ariane launch complexes started at Europe's Spaceport. Russian staff arrived in French Guiana in mid-2008 to assemble the launch table, mobile gantry, fuelling systems and test benches.

- Most of the Soyuz launcher-dedicated installations were like those of Baikonur and minimal modifications had to be made to the Kourou versions of the vehicle, Soyuz-STA and Soyuz-STB, to preserve the overall coherence within Europe's Spaceport, conform to the safety regulations in force and to deal with environmental conditions.

- The main change made by Europe's Spaceport to the operational procedures developed in Baikonur was the integration process, with the introduction of a mobile gantry protecting the rocket from the weather in the lead up to launch and enabling vertical integration of the upper composite.

- The launch vehicle components for this inaugural flight were transported from St Petersburg to French Guiana by ship in November 2009 for the first simulated launch campaign in April and May 2011.

- The construction of the Soyuz launch site was officially completed on 7 May 2011 and Europe's Spaceport was ready for the first Soyuz liftoff from French Guiana.

- On 21 October 2011, Soyuz made its inaugural, three-hour 49-minute flight, successfully deploying two Galileo satellites and starting a new era of launch capability at Europe's Spaceport.

- To date there have been 25 Soyuz launches from Europe's Spaceport. Notable missions include ESA science, Earth observation and navigation satellites such as Gaia, Cheops, Sentinel-1 and Galileo satellites.

- The next Soyuz mission from Europe's Spaceport is planned for November and will carry the latest pair of Galileo satellites to a 23,222 km altitude medium-Earth orbit. These satellites will add to the 26-satellite Galileo constellation already in orbit and delivering Initial Services around the globe.

Table 3: ESA launch history: Ten years of Soyuz at Europe's Spaceport 18)


Launch 1: On 21 October 2011, Soyuz made its inaugural, three-hour 49-minute flight, successfully deploying two Galileo satellites (IOV-PFM and IOV-FM2) and starting a new era of launch capability at Europe's Spaceport. A Soyuz-ST-B/Fregat-MT vehicle lifted off on Oct. 21, 2011 at 10:30 UTC. Flight name: VS-01. — The legendary Russian launch vehicle started its mission after two decades of planning and construction of a brand-new launch complex in South America.


Figure 20: Launch of VS-01, first Soyuz ST-B/Fregat-MT flight from Europe's Spaceport in French Guiana, on 21 October 2011, carrying the first two satellites of Europe's Galileo navigation system (image credit: ESA/CNES/Arianespace)

Launch 2: On 12 October 2012 at 18:15 UTC, Soyuz ST-B/Fregat-MT launched the Galileo satellites IOV-FM3 and IOV-FM4 from Kourou ELS. Flight name: VS-03.

Launch 3: On 22 August 2014 at 12:27 UTC, the first two Galileo FOC satellites,FOC- FM1 and FOC- FM2, were launched from Kourou on the Soyuz ST-B/Fregat-MT vehicle (flight name: VS-09), operated by Arianespace. 19)

Unfortunately, the orbit injection of the FOC spacecraft didn't occur as planned and the satellites did not reach their intended orbital position.

The liftoff and first part of the mission proceeded nominally, leading to the release of the satellites according to the planned timetable, and reception of signals from the satellites. It was only a certain time after the separation of the satellites that the ongoing analysis of the data provided by the telemetry stations, operated by ESA and the French space agency, CNES, showed that the satellites were not in the expected orbit.

The targeted orbit was circular, inclined at 56º with a semi major axis of 29,900 km. The satellites are now in an elliptical orbit, with an eccentricity of 0.23, a semi major axis of 26,200 km and inclined at 49.8º.

According to the initial analyses, an anomaly is thought to have occurred during the flight phase involving the Fregat upper stage, causing the satellites to be injected into a noncompliant orbit.


Figure 21: Photo of the Galileo FOC-3 and FOC-4 satellites fitted onto dispenser (image credit: ESA/CNES/ARIANESPACE-Service Optique CSG) 20)


Figure 22: Illustration of satellite configurations in various mission phases (image credit: OHB System)


Launch 4: The seventh and eighth Galileo satellites (FOC-3 and FOC-4) were successfully launched together on 27 March 2015 (21:46 UTC) atop a Soyuz-STB/Fregat-MT vehicle (Flight name: VS-11) from Europe's Spaceport (Kourou, ELS) in French Guiana. 21) 22)

All the Soyuz stages performed as planned, with the Fregat upper stage releasing the satellites into their target orbit close to 23, 500 km altitude, around 3 hours 48 minutes after liftoff. Shortly thereafter, the two satellites sent their first signals from orbit, which were received by the CNES control center in Toulouse. 23)

Following initial checks, run jointly by ESA and France's CNES space agency from the CNES Toulouse center, the two satellites will be handed over to the Galileo Control Center in Oberpfaffenhofen, Germany and the Galileo in-orbit testing facility in Redu, Belgium for testing before they are commissioned for operational service. This is expected in mid-year.


Figure 23: Artist's view of the protective launcher fairing which jettisoned at 3 min 29 sec after launch, revealing the two Galileo satellites attached to their dispenser atop the Fregat upper stage (image credit: Arianespace, ESA)


Launch 5: The Galileo-9 and -10 satellites (FOC-5 and FOC-6) were launched atop a Soyuz rocket at 02:08 GMT on 11 September 2015 at 02:08 UTC from Kourou ELS, Europe's Spaceport in French Guiana. Flight name: VS-12. 24) 25) 26)

All the Soyuz stages performed as planned, with the Fregat upper stage releasing the satellites into their target orbit close to 23,500 km altitude, around 3 hours and 48 minutes after liftoff. Shortly thereafter, they sent their first "sign of life" to ESOC (European Space Operation Center) in Darmstadt, Germany. Over the next few days, the two satellites will also be undergoing preliminary function testing.

Two further Galileo satellites are still scheduled for launch by end of 2015. These satellites have completed testing at ESA/ESTEC in Noordwijk, the Netherlands, with the next two satellites also undergoing their own test campaigns.

Next year the deployment of the Galileo system will be boosted by the entry into operation of a specially customized Ariane 5 launcher that can double, from two to four, the number of satellites that can be inserted into orbit with a single launch.


Launch 6: The Galileo-11 and -12 satellites (FOC-8 and FOC-9) were launched atop a Soyuz STB/Fregat-MT rocket on 17 December 17, 2015 at 11:51 UTC from Kourou ELS, Europe's Spaceport in French Guiana. Flight name: VS-13. 27)


Launch 7: The Galileo-13 and -14 satellites (FOC-10 and FOC-11) lifted off together at 08:48 GMT on 24 May 24 2016 atop a Soyuz/Fregat-MT rocket from French Guiana. Flight name: VS-15. The twin Galileo spacecraft were deployed into orbit close to 23,522 km altitude, at 3 hours and 48 minutes after liftoff. The coming days will see a careful sequence of orbital fine-tuning to bring them to their final working orbit, followed by a testing phase so that they can join the working constellation later this year. 28)

- "Today's launch brings Europe's Galileo constellation halfway to completion, in terms of numbers," remarked Paul Verhoef, ESA's Director of the Galileo Program and Navigation-related Activities. "It is also significant as Galileo's last flight by Soyuz this year before the first launch using a customized Ariane 5 to carry four rather than two satellites each time – which is set to occur this autumn."

- Known by their nicknames Danielè and Alizée, another two Galileo FOC satellites developed and built by OHB System AG, have been successfully launched on board a Soyuz launcher, which lifted off from the Kourou Space Center in French Guiana. 29)


Launch 8: On 17 November 2016 at 13:06 UTC, a quartet of Galileo satellites (FOC-7, FOC-12, FOC-13 and FOC-14), each with a mass between 715 kg and 717 kg, and a combined liftoff mass of 2,865 kg, was launched and deployed by Ariane 5 into a circular orbit during a mission lasting just under four hours. The Ariane 5 launch, designated Flight VA233 in Arianespace's numbering system, was from the Kourou Spaceport in French Guiana. 30) 31)

Flight VA233 marked Arianespace's first use of its heavy-lift Ariane 5 to loft Galileo satellites, following seven previous missions with the company's medium-lift Soyuz. The Soyuz vehicles carried a pair of Galileo spacecraft on each flight, delivering a total of 14 navigation satellites into orbit since 2011.

The Galileo satellites are at their target altitude, after a flawless release from the new dispenser designed to handle four satellites. Over the next few days, engineers will nudge the satellites into their final working orbits and begin tests to ensure they are ready to join the constellation. This is expected to take six months or so. This mission brings the Galileo system to 18 satellites.


Figure 24: Above Earth's atmosphere, Ariane's aerodynamic fairing is jettisoned and the four Galileo satellites ‘see' space for the first time (image credit: ESA, P. Caril) 32)


Launch 9 : On 12 December 2017, a quartet of Galileo satellites (FOC-15, FOC-16, FOC-17 and FOC18), each with a mass between 715 kg and 717 kg, were launched on Ariane-5 ES in Kourou at 18:36 UTC (flight name:VA-240). The first pair of satellites was released almost 3 hours 36 minutes after liftoff, while the second pair separated 20 minutes later. 33) 34)

- The satellites were released into their target 22,922 km altitude orbit by the dispenser atop the Ariane-5 upper stage. In the coming days, this quartet will be steered into their final working orbits. There, they will begin around six months of tests – performed by the European Global Navigation Satellite System Agency (GSA) – to check they are ready to join the working Galileo constellation.

- This mission brings the Galileo system to 22 satellites. Initial Services of the constellation began almost a year ago, on 15 December 2016.

- "Today's launch is another great achievement, taking us within one step of completing the constellation," remarked Jan Wörner, ESA's Director General. "It is a great achievement of our industrial partners OHB (DE) and SSTL (GB) for the satellites, as well as Thales Alenia Space (FR, IT) and Airbus Defense and Space (GB, FR) for the ground segment and all their subcontractors throughout Europe, that Europe now has a formidable global satellite navigation system with remarkable performance."

- Paul Verhoef, ESA's Director of Navigation, said: "ESA is the design agent, system engineer and procurement agent of Galileo on behalf of the European Commission. Galileo is now an operating reality, so, in July 2017, operational oversight of the system was passed to the GSA. Accordingly, GSA took control of these satellites as soon as they separated from their launcher, with ESA maintaining an advisory role. This productive partnership will continue with the next Galileo launch, by Ariane-5 in mid-2018."

- "Meanwhile, ESA is also working with the European Commission and GSA on dedicated research and development efforts and system design to begin the procurement of the Galileo Second Generation, along with other future navigation technologies."

- Next year's launch of another quartet will bring the 24-satellite Galileo constellation to the point of completion, plus two orbital spares.


Launch 10 : On 25 July 2018 at 11:25 UTC, a quartet of Galileo satellites (FOC-23, FOC-24, FOC-25 and FOC-26) was launched on an Ariane-5 ES vehicle (Flight VA244) of Arianespace from Kourou. The first pair of 715 kg satellites was released almost 3 hours 36 minutes after liftoff, while the second pair separated 20 minutes later. 35) 36)

They were released into their target 22,922 km-altitude orbit ( MEO, 56º inclination) by the dispenser atop the Ariane-5 upper stage. In the coming days, this quartet will be steered into their final working orbits by the French space agency CNES, under contract to the Galileo operator SpaceOpal for the European Global Navigation Satellite System Agency (GSA). There, they will begin around six months of tests by SpaceOpal to verify their operational readiness so they can join the working Galileo constellation.

In July 2017, ESA officially transferred the supervision of Galileo in-orbit operations to the European Global Navigation Satellite Systems Agency (GSA), on behalf of the European Union. After the VA-244 launch, the GSA will be responsible for operating the satellites as soon as they are separated from the launcher. These operations of setting up and operating the system will be done in collaboration with ESA.

The constellation will count 24 operational satellites plus in-orbit spares, of which 22 already have been put into orbit by Arianespace.

Figure 25: Completing the constellation. On 25 July 4 Europe's next four Galileo satellites will be launched into orbit by Ariane 5 from Europe's Spaceport in French Guiana. With this launch the Galileo constellation will reach 26 satellites in space, completing the constellation in overall numbers although further launches are needed to place back-up satellites in orbit. The launch comes at a time when Galileo is into its second year of Initial Operations, with a signal that is better than expected and that is now usable in all new mobile phones. This video looks at Galileo's story so far and the way forward, interviewing Paul Verhoef, ESA Director of Navigation, and Valter Alpe, Galileo's Satellite Production and Launch Campaign Manager (video credit: ESA, Published on 24 July 2018)


Launch 11: Europe's largest satellite constellation has grown even bigger, following the launch of two more Galileo navigation satellites by Soyuz launcher from Europe's Spaceport in French Guiana on 5 December 2021. Galileo satellites 27-28 add to an existing 26-satellite constellation in orbit, providing the world's most precise satnav positioning to more than 2.3 billion users around the globe. 37)

ESA Director of Navigation Paul Verhoef comments: "Today's liftoff marks the 11th Galileo launch of operational satellites in ten years: a decade of hard work by Europe's Galileo partners and European industry, over the course of which Galileo was first established as a working system then began Initial Services in 2016. With these satellites we are now increasing the robustness of the constellation so that a higher level of service guarantees can be provided."


Figure 26: Galileo satellites 27 – 28 lifted off by Soyuz launcher VS26 from Europe's Spaceport in French Guiana on 5 December (4 December at 21:19 local Kourou time), Image credit: ESA/CNES/Arianespace/Optique Vidéo du CSG - S Martin)

Soyuz launcher VS-26, operated by Arianespace and commissioned by ESA, lifted off with the pair of 715 kg satellites from French Guiana on 5 December at 01:19 CET (00:19 UTC, corresponding to 09:19 p.m. Kourou time on 4 December). All the Soyuz stages performed as planned, with the Fregat upper stage releasing the satellites into their target orbit close to 23,525 km altitude, around 3 hours and 54 minutes after liftoff.

"Congratulations Europe! With this 11th launch for Galileo, the constellation is now counting 28 satellites in orbit. Arianespace is proud to guarantee a secure and autonomous access to space with the deployment of Galileo, marking another step towards European independence in satellite navigation," said Stéphane Israël, CEO of Arianespace. "I would like to thank the European Union, especially the European Commission, as well as the European Space Agency, our direct customer for this launch, for continuing to trust us with their satellites." 38)




Mission status

• May 17, 2022: The EU Agency for the Space Program celebrates its first anniversary with new services, a new satellite and even more end users. Time flies when you're busy getting things done. And in the first year of its existence, the EU Agency for the Space Program (EUSPA) of Prague has gotten a lot of things done. 39) 40)

- "EUSPA's launch one year ago today represented the start of a new era for the EU Space Program," says EUSPA Executive Director Rodrigo da Costa. "With an expanded mandate and new responsibilities, we are committed to helping the EU, its citizens and its businesses maximise the many social and economic benefits of space."

- "Today we celebrate EUSPA. It's also the opportunity to reflect and be proud of the milestones we achieved by working together. More users, more services, and satellites in space! Go Europe, go EUSPA!'' concludes EUSPA Administrative Board Chair, Vaclav Kobera.

- Building on the legacy of the European GNSS Agency (GSA), EUSPA's mandate includes not only overseeing the security, services and market uptake of Galileo and EGNOS, but also Copernicus, Europe's Earth Observation (EO) service - an area with significant commercial potential.

- According to the first ever EUSPA EO and GNSS Market Report, published earlier this year, SMEs and start-ups account for more than 93% of European Earth Observation companies. With revenues set to double from approximately EUR 2.8 billion to over EUR 5.5 billion within the next decade, the EO market is full of opportunities for EU businesses and entrepreneurs.

- To ensure companies take advantage of these opportunities, EUSPA has positioned itself as the go-to-source for all things related to Earth Observation. In addition to providing market intelligence, the Agency works directly with businesses to help them best leverage Copernicus data, information and services. EUSPA also launched several EO focused funding opportunities, including Horizon Calls and innovation competitions.

- But Copernicus doesn't exist in a vacuum. It also complements the other components of the EU Space Program, which is why EUSPA is constantly promoting the benefits of using Copernicus, Galileo and EGNOS together.

- "Galileo and EGNOS enable the determination of a precise position, anywhere and Copernicus provides information on the Earth's surface, atmosphere and oceans," adds da Costa. "When you put these programs together, you unleash an array of synergies that can have a powerful impact on society and the planet."

A new pillar for the EU Space Program

- This list of space programs will soon add a new name. GOVSATCOM, the fourth pillar of the EU Space Program, is a user-centric program designed to meet the unique requirements of governmental applications, including those used for crisis management, surveillance and the management of key infrastructures.

- "While Copernicus and EGNOS provide the necessary data and positioning, European governments and institutions need a means of communication that is robustly protected against interference, interception, intrusion and other risks" explains da Costa. "Once operational, GOVSATCOM will bridge this gap between the need for assured and secure communication and the capabilities offered by Copernicus, Galileo and EGNOS."

- As part of its expanded mandate, EUSPA has been entrusted with the procurement of the secure ground segment, its operations and the coordination of the user-related aspects of GOVSATCOM.

The mission remains the same

- EUSPA's first year also saw the development of new services and the launch of new satellites. As to the former, the Agency has been busy developing two new Galileo services: a High Accuracy Service (HAS) for high accuracy Precise Point Positioning (PPP) corrections and the Open Service Navigation Message Authentication (OSNMA), which will provide receivers with a first level of protection against falsifying and spoofing.

- The entry into service of a new additional satellite, GSAT 2203, has brought enhanced accuracy and more precise positioning to the Galileo service provision.

- But even with its expanded mandate and new responsibilities, EUSPA's mission remains the same: linking space to user needs. "I am extremely proud of everything EUSPA has achieved in a year, which is the direct result of our dedicated professionals, all of whom embrace a service-oriented mindset and are passionate about making space technology accessible to EU citizens and businesses," concludes da Costa.

- "It is an honour to serve as Chair of the Security Accreditation Board (SAB), the independent authority that provides accreditation to all of the EU Space Program's components. Thanks to SAB, EUSPA is at the front lines of cybersecurity, providing end-users with the confidence of knowing that the space-derived data they depend on is safe and secure," adds Bruno Vermeire.

• February 2, 2022: A small forest of antennas sprouts from the roof of ESA's Navigation Laboratory, based at the ESTEC technical centre in the Netherlands, which is among the most frequently satnav-fixed locations on Earth. This is also the site of the very first Galileo positioning fix, acquired back in 2014 using the first quartet of Galileo satellites. 41)


Figure 27: Roof of the satnav world at ESTEC (image credit: ESA-Remedia)

- "The antenna is a critical component of any Global Navigation Satellite System user segment, capturing power from the electromagnetic waves it receives, then converting it into electrical current to be processed by the rest of the receiver chain," explains Radio Navigation Engineer Michelangelo Albertazzi.

- "Up here we have a variety of antenna designs in place – such as omnidirectional, high gain and arrays – from leading world receiver manufacturers, which acquire signals from all major global GNSS constellations, including Galileo, GPS, the Russian Glonass and China's Beidou, as well as regional systems such as Europe's EGNOS."

- The NavLab is also equipped with state-of-the-art equipment to record, replay and analyze the RF signals picked up by these antennas, to help with its main goal of performing tests, analyses and characterisation of navigation systems for both ESA and external customers.

• January 3, 2022: A GSTP (General Support Technology Program ) activity with Syntony, France, has taken an existing product used to help signals from satellites reach underground and developed and improved it for navigation purposes. 42)

- The product, called SubWave, is for underground geolocation where GNSS signals from satellites cannot be received. It allows the reception of navigation signals with the normal user's smart phones underground, for example in metro or road tunnels. But there is currently a drawback, which can lead to significant errors in the position being shown.

- The improved system, called SubWave+, has significantly reduced these errors, developing this system into a marketable product. SubWave+ is a dramatic improvement in the system as it brings the accuracy from 10m down to few meters.

- It extends the location service to cover metro or subway stations and their tunnels, compared to the first release of the product, at an affordable price. Using SubWave+ in a tunnel offers a cost reduction compared to the installation of SubWave, since it doesn't require the system to have to split the area into many zones.

- This technological step is designed to be compliant with any GNSS receivers and enable a seamless transition between indoor and outdoor. The developed product is currently being actively sold to world wide customers. Further refinement in the engineering work for the recurrent production is performed by Syntony.


Figure 28: SubWave, is for underground geolocation where GNSS signals from satellites cannot be received (image credit: ESA)

• November 24, 2021: Surrey Satellite Technology Ltd (SSTL) has successfully de-commissioned GIOVE-A, the pathfinder satellite for Europe's Galileo constellation, after 16 years of operations in Medium Earth Orbit (MEO). The decision to de-commission the satellite was made due to the obsolescence in computing systems required for the operation of GIOVE-A, and de-commissioning of the spacecraft took place on 24 November 2021. The procedure involved transitioning the satellite to Earth pointing mode , turning off the reaction wheels and setting the attitude and orbit control system to standby mode, before finally switching off the on board computer and transmitter. 43)

- GIOVE-A was designed, built and tested by SSTL in only 30 months for the European Space Agency (ESA) and was launched on 28 December 2005 with a mission to secure vital frequency filings, generate the first Galileo navigation signals in space, characterise a prototype rubidium atomic clock, and model the radiation environment of MEO for future Galileo spacecraft. GIOVE-A was the first European satellite launched into the demanding MEO radiation environment, where it greatly out-performed its 27 month design lifetime.

- Sir Martin Sweeting, SSTL's Executive Chairman, summed up GIOVE-A's achievements by commenting "GIOVE-A was a milestone mission for SSTL that demonstrated how our pragmatic approach and innovative, low cost, small satellites could deliver critical mission requirements for landmark space programmes, such as Galileo. GIOVE-A secured the vital frequency filings with the International Telecommunications Union (ITU) on the 12th January 2006 and completed its original mission for ESA in 2008. GIOVE-A also over-delivered on its original lifetime and mission goals, and hosted experimental SSTL hardware which provided additional valuable data about the MEO environment for more than ten years – an inspiring and game-changing mission on so many levels."

- "If not for GIOVE-A the 26 Galileo satellites in orbit today would not exist," comments Paul Verhoef, Director of ESA's Directorate of Navigation. "Its speedy development and launch opened the way for our working constellation to follow."

- After completion of its mission for ESA, GIOVE-A was manoeuvred into a higher "graveyard" orbit at 23,300km above the Earth to make way for the first fully operational capability Galileo satellites. In 2012 SSTL took over operations from ESA and GIOVE-A continued to provide valuable in-orbit data on the MEO environment. The Merlin radiation monitor on-board GIOVE-A collected a unique 10+ year record for the MEO orbit and data analysis at the Surrey Space Centre, supported by ESA, showed some interesting features such as the "electron desert" in 2008/9 during what was the lowest solar minimum of the space era, and one of the largest electron storm events on record in April 2010. Several scientific journal papers have been published from the radiation data generated by GIOVE-A and a new model of the outer Van Allen belt electron fluxes, ‘MOBE-DIC', has been produced to help improve future satellite designs.

- Monitoring of the rubidium clocks on board GIOVE-A, key data for the Galileo constellation that followed, revealed no issues during the 6.5 years that the navigation payload was operational.

- Also onboard GIOVE-A was an experimental SSTL GPS receiver, the SGR-GEO, which in 2012 achieved a GPS position fix at 23,300 km altitude - the first position fix above the GPS constellation on a civilian satellite. This demonstrated a new timing and orbital positioning solution for satellites operating in orbits higher than 20,000 km which can only receive a few of the weaker GPS signals that "spill over" from the far side of the Earth.

- The SGR-GEO was subsequently used to track many signals from GPS satellites, including the sidelobes not normally visible to ground-based systems. The performance of GNSS receivers at high altitudes is very sensitive to sidelobe strength, and data from the SGR-GEO helped to map out the antenna patterns of GPS satellites for use in planning navigation systems for future high altitude missions in geostationary orbit , lunar orbit, and beyond into deep space.

- In 2010 SSTL was awarded a contract to assemble, integrate and test the first navigation payloads for the full operational capability Galileo spacecraft, and over a period of 10 years SSTL supplied a total of 34 navigation payloads for Galileo, Europe's global navigation positioning constellation.

- GIOVE-A carries an engraved plaque in tribute to SSTL engineer, Tom Fairburn, who tragically lost his life in the 2004 Indian Ocean Boxing Day Tsunami. Tom worked as a payload mechanical engineer on GIOVE-A and is warmly remembered by colleagues at SSTL.


Figure 29: Photo of the GIOVE-A satellite mounted on the Soyuz Fregate upper stage at the Baikonur launch site, 2005 (image credit: SSTL)

• September 8, 2021: An experimental satellite navigation receiver station high atop Spain's Mallorca island has opened up a novel view of the ever-changing face of the sea. By picking up satnav signals from the far horizon as they bounce off ocean waves, the receivers are able to measure sea surface height down to a scale of centimeters. 44)


Figure 30: Test campaign setup. A pair of satnav receivers atop Mallorca picked up slant angle signals from GNSS satellites to perform reflectometry. Because of the shallow angle, the signals were more likely to maintain coherence than standard near-vertical-angle reflectometry, allowing carrier phase processing to reach an accuracy down to a scale of centimeters. The results were compared to Sentinel-3 altimetry data and an in-situ oceanography buoy (image credit: Institute for Space Studies of Catalonia)

- "We set up a pair of satnav receivers in a near-horizontal orientation, 1400 m above sea level atop Mallorca's highest peak, 4 km from the coast," comments Estel Cardellach of the Institute for Space Studies of Catalonia.

- "Our aim was to receive signals from Galileo, GPS and other Global Navigation Satellite Systems (GNSS) in a way that isn't possible using standard commercial receivers. We pick up satnav signals that have reflected off the sea surface at very slanted, nearly horizontal geometries, then use these results to derive sea surface height and shape."

- "The basic idea behind GNSS ‘reflectometry' is not new," explains ESA microwave engineer Manuel Martín-Neira, who first devised the technique in the early 1990s.

- The concept grew out of the well-established practice of radar altimetry, where radar pulses get bounced down from satellites in orbit to measure the precise contours of Earth's surface. The Copernicus Sentinel-3 pair are the latest contributors to a global altimetry dataset that extends back three decades.


Figure 31: This localization buoy was placed in the sea off Mallorca to help validate results from the GNSS reflectometry test campaign. The satnav receivers can be seen atop the Mallorca skyline (image credit: Institute for Space Studies of Catalonia)

- Manuel had the idea that the satnav signals continuously raining down on Earth from multiple GNSS satellite constellations could be made use of in a comparable manner: comparing original and reflected satnav signals could yield altitude along with additional environmental information. Since then multiple space missions have proven the method.

- He notes: "Standard GNSS reflectometry works like radar altimetry, with orbital satellites receiving reflected signals from straight down, on a nearly vertical orientation. Instead this test campaign has employed a slant geometry, making use of shallow-angle reflected signals from GNSS satellites low on the far horizon.


Figure 32: An experimental satellite navigation receiver station high atop Spain's Mallorca island has opened up a novel view of the ever-changing face of the sea. By picking up satnav signals from the far horizon as they bounce off ocean waves, the receivers are able to measure sea surface height down to a scale of centimeters. A pair of satnav receivers was positioned in a near-horizontal orientation, 1400 m above sea level atop Mallorca's highest peak, 4 km from the coast, seen here with grazing sheep (image credit: Institute for Space Studies of Catalonia)

- "Why do this? Because while a vertical geometry gives a very rough sea surface, at shallow geometries the sea appears more like a mirror – think of the way Venetian blinds can seem variously open or closed depending on how you look at them. This surface smoothness means the reflected signals remain more coherent in turn, potentially allowing us to obtain much higher precision distance measurements."

- This approach is borrowed from a traditional satnav method to boost precision: instead of processing the pseudo-random codes embedded in satnav signals, so-called ‘carrier phase' processing utilizes the much higher-frequency satnav signals themselves, potentially increasing the resulting accuracy from a scale of several meters down to centimeters – although in practice atmospheric effects still need accounting for.

- Estel says: "Our test campaign was supported through ESA's Open Space Innovation Platform to help prepare for a new small reflectometry mission called PRETTY (Passive REflecTomeTry and dosimetry), which will use the same slant geometry in orbit. This miniature ESA CubeSat is being developed by RUAG in Austria and the University of Graz."


Figure 33: The PRETTY CubeSat will perform slant geometry GNSS reflectometry from in orbit. This miniature ESA CubeSat is being developed by RUAG-Austria and the University of Graz. PRETTY is scheduled to launch in the second half of 2022 (image credit: ESA)

- Results from the reflectometry testing will be checked against Sentinel-3 altimetry data of the offshore test areas, along with an oceanographic buoy deployed specially to provide ‘ground-truth' results.

- The Institute for Space Studies of Catalonia's Institute of Space Science unit (IEEC/ICE-CSIC) led the campaign, with the Mediterranean Institute of Advanced Studies (IMEDEA-CSIC/UIB) and Balearic Islands Coastal Observing and Forecasting System (SOCIB) working on the buoy deployment, data recovery, archiving, dissemination and analysis. The German Aerospace Center's Institute for Solar-Terrestrial Physics (DLR-SO) is overseeing analysis of tropospheric and ionospheric interference.

- The receiver station was set up within the military zone of the 7th Aerial Surveillance Squadron of the Spanish Air Force, who also provided electrical power and logistical support.

- "Our test campaign is now over, having run from April to July," adds Estel. "The main reason we aren't observing for longer still is simply the sheer amount of raw data gathered by our receivers: 320 MB per second, adding up to more than a terabyte per hour. While our preliminary indications look promising, it is still going to take several months for us to properly process this gargantuan dataset."

- The testing has already had one significant outcome, explains Manuel: "The main goal of this campaign was to test out how to process data from the PRETTY mission. As we did so, using dual satnav frequencies, we realized the longer-wavelength L5 gives increased coherence compared to L1. So we have proposed switching the working frequency of the single-frequency PRETTY from L1 to L5. Such a change, subject to final technical approval, should greatly enhance the mission's performance."


Figure 34: An experimental satellite navigation receiver station high atop Spain's Mallorca island has opened up a novel view of the ever-changing face of the sea. By picking up satnav signals from the far horizon as they bounce off ocean waves, the receivers are able to measure sea surface height down to a scale of centimeters. A pair of satnav receivers was positioned in a near-horizontal orientation, 1400 m above sea level atop Mallorca's highest peak, 4 km from the coast. The aim was to receive signals from Galileo, GPS and other Global Navigation Satellite Systems (GNSS) in a way that isn't possible using standard commercial receivers. By picking up coherent satnav signals that have reflected off the sea surface at very slanted, nearly horizontal geometries, the campaign can use these results to derive sea surface height and shape to high accuracy (image credit: Institute for Space Studies of Catalonia)

• June 24, 2021: Under the Advanced Shipborne Galileo Receiver Double Frequency (ASGARD) project the technology multinational GMV is collaborating with the defence and security company Saab, to develop a new civil, legislation-compliant, Galileo-signal-using maritime receiver. 45)

- Co-funded by EUSPA (former GSA), ASGARD aims to boost Galileo take up in maritime transport by developing shipborne e-GNSS (European GNSS) data-processing receivers. Ships operating under the International Convention for the Safety of Life at Sea (SOLAS) have to be fitted with a maritime GNSS receiver compliant to the international standards of the International Maritime Organization (IMO).

- GNSS technology is widely used both for ship navigation and positioning applications (traffic surveillance and management, search and rescue, control of fishery vessels, port operations or marine engineering). GNSS's higher capabilities in comparison with traditional maritime navigation methods have made it the preferred navigation resource in many maritime applications.

- In the transport sector as a whole a growing number of regulations enforce GNSS use. Maritime transport is no exception; it is now bound to fit a Positioning, Navigation and Timing (PNT) system that is interoperable in any part of the world. PNT systems are now an obligation in many maritime activities; countries are therefore bound to provide this service for the community and maritime traffic, as a navigation aid in keeping with international recommendations and regulations.

- Satellite navigation can therefore boost the efficiency, safety, and optimization of maritime transport. Galileo and EGNOS, the European Union satellite systems, are making priceless inputs here, with applications taking in all the following: port operations and navigation, localization of spills, improved control of maritime traffic, localization of catastrophes, maritime rescue, ship tracking, improved logistics, ship port approaches, automation, and more efficient port dredging.

- The development of shipborne multi-system radio-navigation receivers (MSR) is now taking a new approach, aiming to provide resilient PNT to improve safety and navigation efficiency. The MSR covers all the shipborne navigation systems and equipment that apply or provide PNT and associated integrity and state information. It calls for support of at least two independent radio-navigation systems; this offers a chance to encourage the use and take-up of e-GNSS (both Galileo and EGNOS) in maritime equipment.

- In this context GMV and Saab will be developing a double frequency multi-constellation maritime receiver navigation system (capable of receiving signals simultaneously from Galileo and other satellite positioning systems) complying with European and international legislation, with the unique ability to provide an additional layer of system safety using Galileo's Open Service-Network Message Authentication (OS-NMA).

- Galileo OS-NMA provides digital signatures of the Galileo Open Service Navigation Messages. It gives the mean for Galileo OS-MNA capable receivers to verify Galileo navigation data received is coming from a Galileo satellite and has not been falsified/spoofed. This verification method provides the Galileo constellation with strong protection, turning it into a more secure and solid GNSS.

- The new maritime receiver represents a new generation of GMV's Galileo receivers and will be integrated into a Saab navigation system in a format that is already well known by the maritime industry. The receiver will be tested according to the requirements of the European Maritime Equipment Directive for GNSS receivers.

- It will additionally be exposed to sophisticated spoofing tests, before being put through a shipborne field test campaign. In addition to coordinating the project GMV will also be responsible for the analysis and consolidation of ASGARD equipment requirements for maritime navigation and its design, implementation, and validation.

- "As with all ESA's main GNSS scientific test campaigns, ESA will archive this precious data at the GNSS Science Support Centre based at ESAC in Spain, a facility of ESA's Navigation Science Office," comments Javier Ventura-Traveset, Head of the Office. This will enable long-term dataset preservation in support of future GNSS reflectometry missions."

Open Space Innovation Platform: opening ESA to new ideas

- Leopold Summerer, heading ESA's Advanced Concepts and Studies Office adds: "This project is a good example of OSIP's core concept: that we receive good ideas from smart people outside ESA, then take rapid action. In this case the idea for the experiment was submitted last year, was quickly matured and judged excellent, then implemented in record time – in the service of one of our future missions."

• June 10, 2021: GMV has been awarded by the European Union Agency for the Space Program (EUSPA) with the contract for the implementation of the Galileo High Accuracy Data Generator (HADG), which will be the facility in charge of generating the high-accuracy corrections data to enable the provision of the Galileo High Accuracy Initial Service (HAS). 46)

- The objective of the HADG is to ensure the continuous provision of HAS data with a proper rate, accuracy, availability, continuity and latency. The data will encompass orbit and clock corrections, biases, quality indicators and service parameters.

- The HADG contract addresses a key infrastructure development under the Galileo program. The Galileo HAS, after all, together with the Open Service Authentication (OSNMA) and the Commercial Authentication Service (CAS), is one of Galileo's standout services, setting it apart from other GNSSs like GPS or GLONASS.

- As defined by the Galileo HAS Implementation Decision published by the European Commission, and further detailed in the HAS Information Note recently published by EUSPA, the HAS will be an open access service based on the provision of high accuracy corrections transmitted in the Galileo E6-B signal (E6, data component), at a rate of 448 bit/s per Galileo satellite connected to an uplink station. The data retrieved by the user from the different satellites offering the HAS will be reconstructed allowing the user to achieve an improved positioning performance.

- GMV, as leader of the project will be responsible for core project activities such as the provision of the algorithms for the computation of the high-accuracy corrections, which rely on GMV's MagicPPP SW suite for Precise Point Positioning. GMV is supported by SIDERTIA in the area of cybersecurity.

- The specification-, design- and development-phases have already been completed and the project is progressing towards the qualification of the system that will enable the execution of the necessary validation activities prior to the HAS initial service declaration (expected in 2022 according to the HAS information note published by EUSPA). This will be a significant accomplishment for Galileo and a new era for the provision of advanced GNSS services in Europe.

- GMV's leading role of in the Galileo High-Accuracy Service is the culmination of a long race and the result of R&D investment made by GMV in pursuit of cutting-edge GNSS high-accuracy solutions. GMV presented the first version of MagicGNSS in 2008, and it is now the core element selected to leverage Galileo HAS to the most advanced position within the public GNSS systems.

• May 12, 2021: Space is essential to the way we live, work and play. The core mission of EUSPA (European Union Agency for the Space Program) is to implement the EU Space Program and to provide reliable, safe and secure space-related services, maximizing their socio-economic benefits for European society and business. By fostering the development of innovative and competitive upstream and downstream sectors and engaging with the entire EU Space community, EUSPA is driving innovation-based growth in the European economy and contributing to the safety of EU citizens and the security of the Union and its Member States, while at the same time reinforcing the EU's strategic autonomy. 47)

EUSPA Mission Statement

The mission of EUSPA is defined by the EU Space Program Regulation. EUSPA's mission is to be the user-oriented operational Agency of the EU Space Program, contributing to sustainable growth, security and safety of the European Union.

Its goal is to:

- Provide long-term, state-of-the-art safe and secure Galileo and EGNOS positioning, navigation and timing services and cost-effective satellite communications services for GOVSATCOM, while ensuring service continuity and robustness;

- Communicate, promote, and develop the market for data, information and services offered by Galileo, EGNOS, Copernicus and GOVSATCOM;

- Provide space-based tools and services to enhance the safety of the Union and its Member States. In particular, to support PRS (Public Regulated Service) usage across the EU;

- Implement and monitor the security of the EU Space Program and to assist in and be the reference for the use of the secured services, enhancing the security of the Union and its Member States;

- Contribute to fostering a competitive European industry for Galileo, EGNOS, and GOVSATCOM, reinforcing the autonomy, including technological autonomy, of the Union and its Member States;

- Contribute to maximizing the socio-economic benefits of the EU Space Programme by fostering the development of a competitive and innovative downstream industry for Galileo, EGNOS, and Copernicus, leveraging also Horizon Europe, other EU funding mechanisms and innovative procurement mechanisms;

- Contribute to fostering the development of a wider European space ecosystem, with a particular focus on innovation, entrepreneurship and start-ups, and reinforcing know-how in Member States and Union regions.


- EUSPA is the operational European Union Agency for the Space Program. It adopts a user-oriented approach to promote sustainable growth and to improve the security and safety of the European Union.

- Over the past twenty years, the European Union has been committed to creating an EU Space Program and infrastructure that is competitive, innovative, and that delivers real benefits to citizens and business alike. Building on these foundations, the European Space Programme has made great leaps forward in recent years, delivering unique services in satellite navigation, Earth observation, and telecommunications, and strengthening both the upstream and downstream sectors.

- As a result, space technology, data and services are indispensable to the daily lives of Europeans. They also play an essential role in supporting the strategic interests of the Union. Space-based services are ubiquitous - we all use them when we use our mobile phones. In addition, a growing number of industries and entrepreneurs look to space to develop solutions to the challenges we face in society. Nevertheless, at EUSPA we believe that we have just scratched the surface of the benefits that space can deliver. We see a future that is very close, where business and society will increasingly look to space as the resource of the future.

- As the link between space and users, EUSPA's ambition is to become the reference point for all space-related needs in the EU. EUSPA brings all space stakeholders together, allowing them to leverage the synergies of the Space Program's individual components to deliver the greatest possible benefits to European citizens and business. EUSPA plays a leading role in the EU Space Programme implementation. It promotes space-based scientific and technical progress and supports the competitiveness and innovative capacity of space sector industries within the Union, with a particular focus on small and medium-sized enterprises (SMEs) and start-ups.

- The EU Space Program and the services and applications that it supports, help to advance the European Union's objectives and to achieve its key policy goals and priorities.


Our values serve as a compass for all our actions and guide how we interact with the world.

- We care about each other and the people we work with; we believe in European values and take our corporate social responsibility seriously.

- We are respectful and diverse. We value and respect people, the environment, the EU institutions and their roles; we encourage diversity and provide equal opportunities for all.

- We are professional. We continuously develop and improve our knowledge, processes, skills and competencies to deliver high quality, cost effective services with integrity and high ethical standards.

- We are innovative. We continuously search for ways to stimulate innovation in our work and the work of our partners to improve our performance and excel in our mission.

- We are reliable. Together, as one team, we are trusted partners to our colleagues across the Agency and to our stakeholders.

- We are accountable. We take responsibility for our work and reach decisions based on due diligence.


- In 2021, in line with the new EU Space Regulation and the growing role of space in supporting EU priorities in terms of growth, competitiveness, sustainability, and security, the EU decided to expand the scope of the former European GNSS Agency (GSA) to include new responsibilities. This resulted in the creation of the EUSPA, which was officially launched on 12 May 2021.

- EUSPA builds on the proven track record of the GSA. In taking on responsibility for various new Space Programme components, EUSPA leverages the GSA's technical expertise, market intelligence, security know-how, and the extensive EU space-based community that it has built, to create synergies that will take EU space services and applications to a new level both in Europe and around the world.

- The EUSPA story begins with the Galileo Joint Undertaking (GJU) set up in May 2002 by the European Community and the European Space Agency to manage the development phase of the Galileo Program.

- Two years later, the European GNSS Supervisory Authority (GSA) - the GSA's predecessor - was initially established as a Community Agency on 12 July 2004, by Council Regulation (EC) 1321/2004, status amended in 2006 by Council Regulation (EC) No 1942/2006. The European Council took this important step because it recognized the strategic value of Europe having its own independent satellite positioning and navigation program, namely EGNOS and Galileo, and the need to ensure that essential public interests in this field are adequately defended and represented.

- The GSA officially took over all tasks previously assigned to the GJU on 1 January 2007.

- With Regulation (EU) No. 912/2010, which entered into force on 9 November 2010, and subsequently amended by Regulation (EU) No. 512/2014 of 16 April 2014, the GSA was restructured into an agency of the European Union named the European GNSS Agency (GSA).

The Regulatory Framework of the GSA

- The main legal framework currently applicable to the Agency is available in the Register of documents, which you can find here.

• May 01, 2021: Satellites provide crucial data on climate and environmental changes every day. The European Global Navigation Satellite System Agency GSA has now commissioned RUAG Space to conduct a study to increase the accuracy of real-time satellite navigation. 48)

- Satellites provide crucial data on climate and environmental changes every day. The European Global Navigation Satellite System Agency GSA has now commissioned RUAG Space to conduct a study to increase the accuracy of real-time satellite navigation.

- For climate and environmental research, satellites provide extremely important data every day, such as how high sea levels are rising or what effects global warming is having on glacier ice shrinkage in the Alps.

- A new study aims to further increase the accuracy of this space data from climate and environmental satellites. To make this possible, the Prague-based European Global Navigation Satellite System Agency (GSA) awarded a one-million-euro research contract to RUAG Space earlier this year. Headquartered in Zürich, the leading aerospace supplier in Europe is also one of Austria's largest space technology companies, with its headquarters in Vienna.

- To provide precise Earth observation data from space, the satellite's position in space must be known as accurately as possible. To determine the exact position of satellites, RUAG Space's navigation receivers today use the signals from the 22 European Galileo navigation satellites.

- "Currently, there is still untapped potential in the Galileo satellites. They transmit several signals. On one of these signals, a new service, the High Accuracy Service (HAS), will support significantly improved positioning from 2022," explains Martin Auer, who is leading the study at RUAG Space.

- "When this new service goes into operational use, it will need equipment that can do something with it. That's what we're working on." By the end of 2022, RUAG Space will develop a new product in Vienna that will be able to use the new Galileo HAS service.

- Quantum leap: five times more accurate positioning thanks to software update However, navigation receivers from RUAG Space that process Galileo signals already ensure precise positioning. These include the Sentinel-6 environmental satellite, which has been in space since November 2020. It measures the amount of sea level change and provides crucial data on coastal areas at risk from sea level rise.

- "The more accurate the satellite's position can be determined, the more precise the environmental data it collects and provides. With the more accurate data, for example, the danger to coastal cities such as Venice can be predicted more effectively" declared Fiammetta Diani, Head of Market Development at GSA.

- RUAG Space is developing a software update for navigation receivers of the current PODRIX receiver generation already in space, such as those used for Sentinel-6. This will enable these receivers to increase the accuracy of satellite positioning from the current level of about one meter to 20 centimeters. "This is a dramatic improvement - a quantum leap - in accurate satellite positioning that will contribute to much better climate and environmental data," says Heinz Reichinger, the product manager responsible at RUAG Space.

• April 28, 2021: The Agency welcomes the European Parliament's position expressed today, confirming the political agreement on the Space Regulation reached in December 2020 and the creation of the European Union Agency for the Space Program (EUSPA). The EU Space Program, with the largest budget ever for Space - €14.88 billion, encompasses all EU space activities under one roof and will allow for an effective and efficient contribution to the priorities of the European agenda. 49)

- The EU Space Program will ensure the continuity and evolution of the existing flagships Galileo/EGNOS and Copernicus. It will also support new initiatives, in particular the European Union Governmental Satellite Communications (GOVSATCOM), SSA (Space Situational Awareness), and potentially others follow.

- The regulation gives the means to the European Union to maintain its position as a global space power and lay the foundation for EU's new Space ambition. With the new setup, the European Union will scale up its promotion of innovative downstream applications/technologies, the user and market uptake and the unleash the huge potential of space data and services to develop value-adding applications and services. Moreover, the space data and services provided under the EU Space Programme will support the green and digital transformation, which is the cornerstone for the European recovery initiative.

- Rodrigo da Costa, GSA/EUSPA's Executive Director, stated: "EUSPA is ready to implement the EU Space Program and join hands with our partners to make the EU space ambitions a reality. We will boost our support to reinforce the dynamic and innovative downstream sector because we want society to benefit even more from space-based services. We will continue delivering and enhancing safe and secure navigation services for the EU citizens and the Member States. We are committed to getting the best out of the EU Space Program components, in particular Galileo, EGNOS, Copernicus and the upcoming GOVSATCOM, and are ready to contribute to new initiatives such as space-based secure connectivity."

- The EU Agency for the Space Program (EUSPA) replaces and expands on the European Agency for Global Navigation Satellite Systems (GSA) and evolve its mandate.

- In addition to the exploitation management and operational security of EGNOS and Galileo, EUSPA will be in charge of the security accreditation of all the components of the EU Space Program, and of the coordination of user-related aspects of GOVSATCOM, in close collaboration with Member States and other involved entities such as EU Agencies. The Agency will be responsible for promoting the commercial market uptake of Galileo, EGNOS, and now also Copernicus together with the Entrusted Entities of the European Earth Observation program, with a special focus on the synergies of all components of EU Space.

- The EU Space Program Regulation will provide the backbone for supporting the space industry and will foster Europe's space technological autonomy and resilience, to compete in the global race. It will also help the economy and society recover from the crisis resulting from the COVID-19 pandemic. Moreover, it will finance programs that leverage space for a stronger and more prosperous Europe in the years and decades to come for the EU citizens and businesses.

Next Steps

- The Regulation will be published in the Official Journal in the coming days, allowing it to enter into force the day of publication marking the first day of EUSPA. The Regulation will retroactively apply from 1 January 2021. Then, the Financial Framework Partnership Agreement (FFPA) and the relevant Contribution Agreements with the European Commission and ESA in order to implement the Regulation will be signed with the European Commission.

• April 18, 2021: Galileo: finding our way. 50)

Figure 35: More than two billion smartphones, with users worldwide are now making use of Europe's Galileo navigation satellite constellation. But how do satellites thousands of kilometers away in space manage to tell you where you are and where you're going? Simply being so far away is part of the answer - learn the details of the world's most precise navigation system in this new video (video credit: ESA)

• April 6, 2021: Today is 406 Day – the annual campaigning day to spread awareness of the importance of emergency beacons, and the satellites that pick up their signals, including Europe's Galileo constellation. As well as letting people across the world find their way, Galileo also serves to detect SOS messages and relay them to authorities, contributing to saving many lives. 51)

- Such detections can happen anytime, but one recent high-profile incident happened in the midst of the Vendée Globe solo round-the-world yacht race. Skipper Kevin Escoffier had his boat smashed to pieces by fierce waves in the Southern Ocean.


Figure 36: Stranded sailors in liftraft use an emergency position-indicating radiobeacon (EPIRB) to call for help (image credit: GSA)

- He took to his life raft. As it hit the water it automatically activated his rescue beacon, transmitting a 406 MHz SOS signal for automatic pickup by participating satellites, courtesy of the Cospas-Sarsat satellite-based emergency detecting and locating system. The signal allowed the race authorities to localize Kevin's position within a matter of minutes and send nearby boats to the rescue.

- The only system that can independently locate a beacon anywhere on Earth's surface, Cospas-Sarsat has helped save thousands of people since it was first established in 1982. Originally the system operated through transponders hosted aboard either low-Earth orbit or geostationary satellites.

- In the last decade Galileo joined Cospas-Sarsat – supported by the European Commission, the system's owner – driving a significant increase in performance. Because they have such a high orbital altitude, at 23,222 km up, while still moving steadily through the sky, Galileo satellites combine broad views of Earth with the ability to facilitate quick determination of the position of a distress signal through a combination of time-based and Doppler ranging.

- International 406 Day – taking its name from the radio frequency used by Cospas-Sarsat beacons, and the US order of today's date – seeks to remind beacon users to take care to check their batteries and functionality. Such beacons are used aboard boats and ships, also aboard aircraft and are also carried by hikers in the wilderness – anywhere beyond the reach of standard phone-based emergency services.


Figure 37: For three decades the Cospas–Sarsat system has used relays on satellites such as Europe's MSG and MetOp to pick up distress calls from ships and aircraft (image credit: Cospas-Sarsat)

- All the same, an SOS signal can reach the authorities surprisingly swiftly, within a few minutes. First the signal from the beacon is detected automatically by the search and rescue payload aboard participating satellites – often more than one at once – then pinpoints its source on Earth's surface.

- Next, this information is relayed – via a set of stations on the corners of Europe, in the case of Galileo-detected signals – then passed to the nearest national rescue center, at which point the rescue can begin.

- The beacons themselves are surprisingly compact in size, typically the size of a medium-sized flashlight. But the search and rescue payloads carried aboard the Galileo satellites in orbit are similarly modest. At only 8 kg in mass, these life-saving payloads consume just 3% of onboard power, with their receive-transmit repeater housed next to the main navigation antenna.

Figure 38: Galileo satellites are placed in medium orbits, at 23,222 km altitude along three orbital planes so that a minimum of four satellites are visible to user receivers at any point on Earth. The satellites continuously broadcast navigation messages, allowing receivers to pinpoint their position. They also relay search and rescue messages received worldwide (image credit: ESA)

- All but the first two of the 26 Galileo satellites in orbit carry these payloads, with two more satellites scheduled to add to their number later this year.

- Galileo's Search and Rescue service is Europe's contribution to Cospas-Sarsat, operated by the European Global Navigation Satellite System Agency, GSA, and designed and developed at ESA.

- The Cospas-Sarsat satellite repeaters are supplemented by a trio of ground stations at the corners of Europe, known as Medium-Earth Orbit Local User Terminals (MEOLUTs), based in Norway's Spitsbergen Islands, Cyprus and Spain's Canary Islands and coordinated from a control centre in Toulouse, France.

- This trio is soon to become a quartet, with a fourth station on France's La Reunion Island in the Indian Ocean.

- Galileo's participation in Cospas-Sarsat has led in turn to a service innovation – from last year, Galileo has been replying to SOS signals with ‘return link messages', assuring those in peril that their signals have been received and help is on the way.

• March 10, 2021: In a first for any satellite navigation system, Galileo has achieved a positioning fix based on open-service navigation signals carrying authenticated data. Intended as a way to combat malicious ‘spoofing' of satnav signals, this authentication testing began at ESA's Navigation Laboratory – the same site where the very first Galileo positioning fix took place back in 2013. 52)


Figure 39: Signal testing. Satellites of all kinds have one central characteristic in common. They all have to reach out either to receive commands, transmit scientific findings, relay telecommunications, perform remote sensing or, increasingly, deliver precision navigation and timing data – relying on radio frequencies (RFs) to do so. ESA's Radio Frequency Systems, Payload and Technology Laboratories perform RF research for both the space and ground segments. The main Lab is made up of five facilities: the General Microwave Lab, Radio Navigation Lab, Telecom Lab, Remote Sensing Lab and RF High-Power Lab (external), image credit: ESA

- These historic first authenticated signal ‘position, velocity, timing' fixes were made using a total of eight Galileo satellites for around two hours on 18 November 2020. The tests represent a first proof of concept for an eventual operational service offering positioning with authenticated data to users.

- Spoofing has, for instance, been demonstrated as a means of forcing down drones or redirecting ships, while some high security locations – as well as disrupted international borders – have become notorious for spoofing signals that prevent the reliable use of satnav in their vicinity.

- "When a receiver picks up a navigation signal from a satellite, up until now it has no way of confirming that was indeed its source," comments navigation engineer Stefano Binda, overseeing the project for ESA.

- "This can result in ‘spoofing' – malicious people and organisations using false signals to mislead users about their actual position. This authentication service offers a way to prevent such deception."


Figure 40: Satnav spoofing. Counterfeit satellite navigation signals can mislead user receivers on the ground, causing them to misidentify their position with potentially serious consequences. A new software suite called SimSAFE, developed by an Italian company called Qascom with ESA backing, allows prototype receivers to be tested and tuned against simulated spoofing attempts (image credit: Qascom)

- Stefano notes: "In recent years this problem has become sufficiently pronounced as a weak point that the European Commission, ESA and European GNSS Agency (GSA) decided to develop signal authentication as a differentiator for Galileo."

- An ESA Navigation Directorate team at the Agency's ESTEC technical centre in the Netherlands worked with their GSA counterparts at the twin Galileo Control Centers (GCCs) in Italy and Germany and the Galileo Service Centre (GSC) in Spain.

- "In everyday authentication you might send a document that has been digitally signed, where both sender and recipient use compatible cryptographic keys to validate the document's source of origin," adds Stefano.


Figure 41: Drones can be downed by spoofing. INVOLI drone. ESA BIC Switzerland start-up INVOLI provides a solution to increase air traffic awareness on existing drone systems, without modifying the drone's hardware. Meet INVOLI at the 10th ESA Investment Forum in ESOC 31 January 2019 (image credit: INVOLI)

- "In everyday authentication you might send a document that has been digitally signed, where both sender and recipient use compatible cryptographic keys to validate the document's source of origin," adds Stefano.

- "In this case we were working with a constrained amount of bandwidth within the navigation signal, so instead opted for a ‘delayed key' approach. This means the initial data come along together a short tag which, within a short stretch of time usually not exceeding 30 seconds, is followed by a key, which is able to validate the tag and authenticate the data associated with it."

- During the test campaign, the Galileo Control Centers send the navigation signal to the GSC for the addition of the authentication code, which is then returned for uplink to the satellites, to be received and authenticated by the test receivers at ESTEC's Navigation Lab and elsewhere in Europe, in participating laboratories.

- To enable the authentication test campaign, Thales Alenia Space in France served as prime contractor to upgrade of the ‘Galileo Mission Segment' – the world-spanning system that determines and create the navigation messages broadcast by Galileo satellites. Thales Alenia Space in Italy was responsible for the system level integration. No modification of onboard satellite systems has been required to support Open Service Navigation Message Authentication (OS NMA), as spare bandwidth was made use of.

- "We used our standard laboratory Septentrio test user receivers with a software add-on," comments Stefano. "The beauty of this approach is that receivers will be able to make use of the future authenticated service without needing any new hardware, only software updates – apart from additional measures that might be mandated for operation in practice."

- ESA and GSA are continuing their authentication testing, with a view to introducing an operational Open Service Navigation Message Authentication service for users in the near future.


Figure 42: Open Service Navigation Message Authentication (image credit: ESA)

• January 11, 2021: The end of 2020 marked a notable milestone for Europe's Galileo First Generation, as the program chalked up its 500th ESA Engineering Board. 53)


Figure 43: Circular L-band (navigation) and hexagonal (SAR) antenna (image credit: Galileo GNSS)

- Since the first such ‘G1' Engineering Board in 2008 a total of 26 Galileo satellites have been built, tested and flown, with a further 12 ‘Batch 3' satellites set to join them in orbit during the coming decade – these satellites are currently being finalized at OHB Systems in Bremen, Germany, then tested at ESA's ESTEC Test Centre in the Netherlands.

- The Galileo system's globe-spanning ground system has also been put in place and made operational. Galileo began initial operations in December 2016 and is today the world's single most accurate satellite navigation system, serving more than 1.5 billion smartphones and devices. But all that effort owes its origins to the regular sequence of G1 Engineering Boards.

- Much like a modern version of the Agora public square of ancient Greece, Galileo's ESA Engineering Board is the forum where technical experts regularly meet with a clear objective: maintaining, reviewing and updating the Galileo Project technical baseline, the STRB (System Technical Requirements Baseline).

- This STRB drives the implementation of the Galileo System and its infrastructure, namely the space and ground segments, along with associated interfaces and operations. All in all, the G1 system technical specification under ESA responsibility adds up to more than 22,000 separate requirements – both unclassified and classified in nature, with considerable interdependencies which all need to be controlled in configuration.

- The Galileo G1 Engineering Board is chaired by ESA in accordance with its role as Galileo System Design Authority, assigned to it by the European Commission.

- For more than 12 years now, ESA and industry engineers from all relevant disciplines – covering system, satellite, ground, signal, radio-navigation, RAMS (reliability, availability, maintainability and safety), security and infrastructure – have put their best skills at the disposal of this Board. It continues to be a crucial enabler for further robustness improvements and new service evolutions.

- The G1 Engineering Board meetings will continue into the future, complemented with the Engineering Boards for the new Galileo Second Generation (G2 satellites are planned for later this decade) which are already well underway.

• August 14, 2020: With 26 satellites now in orbit and over 1.5 billion smartphones and devices worldwide receiving highly accurate navigation signals, Europe's Galileo navigation system will soon become even better, ensuring quality services over the next decades. 54)

- Following the European Commission's decision to accelerate development of Galileo Next Generation, ESA has asked European satellite manufacturers to submit bids for the first batch of the Galileo Second Generation (G2) satellites. The new spacecraft are expected to be launched in about four years.

- The next-generation satellites will provide all the services and capabilities of the current first generation, together with a substantial number of improvements as well as new services and capabilities.

- "We want an ultra-flexible and mostly digital design," says Paul Verhoef, ESA Director of Navigation.

- "Developing the second generation is challenging for both industry and for ESA. In 2024, we need to launch the first satellites for this new state-of-the-art constellation."