On May 31, the European Space Agency (ESA) announced the main procurement batch of Galileo Second Generation (G2), initiated in summer 2022, has been finalized. The system is now ready for its on-orbit validation development phase.
Following the opening session of the European Navigation Conference (ENC), Javier Benedicto, director of navigation for the ESA, invited Thales Alenia Space, Airbus Defence and Space, and Thales Six GTS to sign contracts commencing system engineering support for the next generation of Europe’s navigation satellite system.
Satellite-building contracts were awarded in May 2021 to Thales Alenia Space and Airbus Defence and Space to create two independent families of satellites amounting to 12 G2 satellites in total. Separate contracts were also awarded to Safran Electronics and Defence-Navigation and Timing and Leonardo to provide the ultra-precise atomic clocks carried aboard.
Employing electric propulsion for the first time, and hosting a higher-strength navigation antenna, the G2 satellites will incorporate six (rather than four) enhanced atomic clocks as well as inter-satellite links to communicate and cross-check with one another. They will be controllable with an increased data rate to and from the ground and will operate for 15 years on orbit.
In addition, G2’s fully digital payloads are being designed to be easily reconfigured on orbit, enabling them to respond to the evolving needs of users with novel signals and services.
There are 28 Galileo satellites on orbit, making it the most precise satellite navigation system —providing meter-level accuracy to more than four billion users around the globe. There are 10 Galileo satellites due to be launched, after which the first of the G2 satellites with enhanced capabilities are expected to join the constellation in the next few years.
GMV has been selected by the European Space Agency (ESA) and the European Union Agency for the Space Programme (EUSPA) to develop the Galileo second-generation system test bed (G2STB). The G2STB will provide ESA with a key system verification and validation facility in support of its role as Galileo system development prime, enabling a wide range of Galileo system monitoring, troubleshooting, prototyping and experimentation activities.
GMV will deliver four G2STB versions over five years. Among these modules, the G2 high accuracy service (HAS) data generator and monitor aims to improve the Galileo HAS that was declared operational in January.
Other early capabilities of the G2STB include an upgraded orbit determination and time synchronization facility — capable of processing inter-satellite link data, a time service monitoring module, an integrity support message generator, a signal authentication service, an authentication validation module, an emergency warning service module, an ISL simulator and a G2G message composer.
The G2STB project aims for a smooth transition from the Galileo first-generation to the second-generation, building onto the G1G legacy system tools. The G2STB is one of the key infrastructure elements that ESA is developing for the correct functioning of the Galileo second-generation satellites.
The G2STB will eventually replace and upgrade the capabilities of the two first-generation facilities, the Galileo system evaluation equipment and the time and geodetic validation facility (TGVF-X). The latter, developed and operated by GMV over the last decade, has played a key role in monitoring the Galileo signals and system validation activities during the Galileo exploitation phase. The TGVF-X is also contributing to the early validation of new capabilities and elements being rolled out in recent and upcoming Galileo System updates.
In parallel to the development phase, the G2STB will help upgrade the network of Galileo experimental sensor stations to process new signals and capabilities to ensure the availability of a G2-capable, worldwide, multi-constellation network of receivers and bit-grabbers — independent from the operational Galileo sensor stations.
News from the European Space Agency (ESA). Europe’s first generation Galileo constellation is already the world’s most precise satellite navigation system — delivering meter-scale positioning to more than 3.5 billion users worldwide. The Galileo Second Generation will enable even better performance and an expanded range of services.
Essential elements of the G2 system are being evaluated in ESA laboratories, including key algorithms to synchronize satellite timing and determine orbits, as well as test versions of a GNSS receiver and emergency beacon.
Two independent families of satellites, totaling 12 G2 satellites, are being procured by Thales Alenia Space in Italy and Airbus Defence & Space in Germany. With their first launches due in the middle of this decade, G2 satellites will be much larger than existing Galileo satellites, and they represent a major technical step forward.
Backwards-compatible with the current constellation, the G2 satellites will incorporate numerous technology upgrades, developed through EU and ESA research and development programs. They will employ electric propulsion for the first time and host 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.
The GNSS antenna farm on the ESTEC roof for live signal reception. (Photo: ESA)
Algorithms at the heart of G2
At the heart of satellite navigation is the ability of the satellites to determine where they are in space and the precise time down to a few billionths of a second as they transmit their navigation signals. The greater the precision of these factors, the greater the accuracy of the positioning for users, because Galileo receivers take the time between the signals being transmitted and received and turn it into a measurement of distance. Signals from four or more satellites are used to pinpoint the receiver’s location.
The Advanced Orbit Determination and Time Synchronisation (ODTS) Algorithms Test Platform evaluates the advanced software that will perform these calculations for G2. Developed by Thales Alenia Space through an EU Horizon 2020 project coordinated by ESA, the platform is now installed and running in ESA’s Navigation Laboratory. The laboratory is based at ESA’s technical heart, the ESTEC establishment in the Netherlands, where it is helping simulate how the G2 satellites will operate in practice.
“This platform represents a dynamic, highly-performing environment for algorithm experimentation in both real-time and post-processing modes, using either real or simulated data,” said Francisco González, the project’s technical officer. “It contains the algorithmic core of Navigation for Earth Orbit Determination and Identification Segment, NEODIS, which is the suite of algorithms developed by Thales Alenia Space for precise orbit determination of the satellite constellation. These algorithms allow the real-time estimation of orbits and clocks, as well as the generation of Galileo navigation messages, with an estimated accuracy in the tens of centimeters.”
“Important evolutions aimed at improving the estimation of clocks and orbits are being incorporated,” said Gustavo Lopez-Risueno, head of ESA’s Galileo G2 System Engineering Unit. These improvements include:
integration of composite clock algorithms for a stable and robust reference timescale
the dynamic modeling of satellite and station clocks based on their known behavior
the processing of auxiliary measurements such as laser range measurements, in which lasers are reflected off of satellites to measure their orbital position, delivering a ranging accuracy down to under a centimeter —significantly better than the half-meter or so available from radio ranging
intersatellite links.
The first G2 receiver prototype “breadboard” is now running in ESTEC’s Navigation Lab. (Photo: ESA)
First G2 receiver up and running
Another outcome of ESA-led H2020 research is also up and running in the lab: the first G2 receiver prototype “breadboard,” developed by GMV.
“Its development has been key to supporting the fine-tuning and assessment of some signal design options we are considering,” said Jose A. Garcia-Molina, who leads the G2 signal-in-space design at ESA. “Representative mass-market receiver processing architectures and techniques have been considered to assess the final benefits a user would receive.”
“This first G2 receiver breadboard allows us to better understand the performance G2 can achieve in different user conditions, such as the urban environments in which many Galileo users are based today,” said Miguel Manteiga Bautista, who leads ESA’s G2 Programme.
Meanwhile, two parallel activities have been started for development of the G2 test user receiver. The receiver will be taken outside the lab for various test activities ahead of the first G2 launches, and then again for in-orbit testing and validation.
Arctic Mass Rescue Operation in 2021 tested the rescue of 200 cruise-ship passengers using Galileo SAR. (Photo: EUSPA)
Search-and-rescue system also being updated
Nearby, in ESTEC’s Telecommunications Lab, is the G2 search and rescue test beacon simulator, now operational following site acceptance testing.
Like their first-generation predecessors, the G2 satellites will pick up emergency signals from beacons on Earth and relay them to a ground station, which will forward them to local emergency services. This contributes to emergency response saving more than 2,000 lives annually.
Emergency position-indicating radio beacon (EPIRB). (Photo: ESA)
The new simulator to model the performance of these emergency beacons was developed over three years by Thales Alenia Space, under ESA leadership through a G2G System Engineering Technical Assistance Activity.
“Equipped with state-of-the-art signal generation and processing capabilities, coupled with a 200 W amplifier, this new simulator offers several enhanced functionalities over first-generation simulators, including the transmission of the new G2 beacons developed by the Cospas-SARSAT organization and the simulation of complex operational scenarios of up to 15 parallel distress beacons,” said Eric Bouton, ESA’s Galileo search and rescue engineer.
“Its development is really a crucial step to gaining a better understanding of the in-orbit behavior of Galileo’s First and Second Generation search-and-rescue payloads with the new waveforms of the G2 beacons and with the growing beacon population and associated alert traffic,” Bouton said. “It will be used for an initial test campaign already in preparation, and in the future to support the commissioning of all new Galileo search-and-rescue systems.”
Testing on Galileo’s second-generation hardware has begun.
Test versions of the satellites’ navigation payloads is undergoing evaluation by Airbus Defence and Space at its Ottobrunn facility in Germany and by Thales Alenia Space at the ESTEC technical center in the Netherlands of the European Space Agency (ESA).
Known as the Galileo Payload Testbeds (GPLTBs), these are development models of the navigation payloads intended for the Galileo Second Generation (G2) satellites. The navigation antennas of the testbed payloads are being testing to check whether they meet the ambitious performance levels set for the G2 satellites.
Instead of being assembled from space-ready components like an actual satellite payload, the GPLTBs are built from electronic parts placed in test racks, with a proof-of-concept version of a navigation antenna attached.
“The goal with these test campaigns is to prove their design concepts early, and anticipate any technical issues that might arise as early as possible,” said Cédric Magueur, ESA’s payload manager for the Thales G2 satellites.
“These campaigns also make it possible to develop and validate new performance measurements concepts for these new generation of complex navigation payloads,” said 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.”
The second satellite in the European Data Relay System (EDRS) undergoes tests at Airbus’s Compact Antenna Test Range facility. (Photo: ESA)
“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,” Cédric said. “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.”
There are 26 Galileo satellites now in orbit; deployment of 12 more will begin by the end of this year. Next will come the first 12 G2 satellites, featuring enhanced navigation signals and fully digital payloads. The 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 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. The metal-walled chambers are isolated from external radio interference, with inner walls 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,” Cédric said. “These test campaigns mark the first time that their performances will be confirmed in terms of radiating signals. 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, a pair of paraboloid reflectors. In this way, the signal from the testbed can be reshaped as if it had traveled the long distance that actual Galileo signals need to travel, from an altitude of 23,222 km down to Earth’s surface.
At Airbus, the testing is being undertaken in reverse order, with the far-field measurements taking place before performing the near-field measurements.
With 26 satellites now in orbit and more than 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.
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.
Paul Verhoef, director of the Galileo Programme. (Photo: ESA)
The next-generation satellites will provide all the services and capabilities of the current first generation with a substantial improvements and new services and capabilities.
“We want an ultra-flexible and mostly digital design,” said 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.”
Invitation to Tender
Following almost 24 months of a competitive dialogue procedure with the three large system integrators involved, ESA issued a “Best and Final Offer” invitation to tender on Aug. 11 to Airbus, OHB System AG and Thales Alenia Space.
ESA is implementing a dual-sourcing approach, and two parallel contracts are expected to be signed by the end of 2020 among the current three bidders. Under the plan, each of the two selectees will build two satellites for development purposes, with options for up to 12 satellites in total.
The first satellites of the new constellation are expected to be launched before the end of 2024, together with updated ground systems to support the new satellites.
Reconfigurable in Orbit
In addition to being more powerful, the second-generation Galileo satellites will be more flexible, able to be reconfigured in orbit in order to satisfy the expected evolution in end-user needs.
A number of challenges exist for the bidders. The goal of a digital and fully flexible design represents the cutting edge of industrial capability.
Navigation Antenna Progress
A Galileo satellite undergoes its fit-check validation at the Kourou Spaceport in French Guiana. (Photo: ESA/Arianespace)
Furthermore, the required navigation antennas will have a very advanced design; much research and development by ESA has been done, yet more remains for industry.
ESA has already built such an antenna as a proof of concept at the Agency’s ESTEC technology center in the Netherlands to ensure feasibility, and the know-how has been shared with the three bidders.
“Each bidder must determine how they can best manufacture the navigation antenna, and we’ll have to see how each proposes to do it. Also, requiring a fully flexible payload is quite a challenge. No such navigation spacecraft of that type have flown yet,” Verhoef said.
Ambitious Plan
The European Commission has decided that what was previously going to be called the “transition batch” of new satellites will now become, in fact, the Galileo Second Generation satellites. The European Commission and EU Member States have already made clear that they want to be very ambitious and further increase the technical capabilities of the Galileo system.
The name change reflects of how the current batch is actually shaping up.
The transition satellites were initially foreseen as interim upgrades, to cater for the potential risk of late delivery of the later, completely new and very advanced G2 satellites.
Estimated Lifetime Increased
Based on constant measurements of the performance of the current satellites in orbit, their predicted lifetime has increased. So, together with a slight spreading out of the launches of the Batch 3 satellites — currently under construction by OHB and in testing at ESTEC —this will ensure service continuity before the new, advanced capabilities of Galileo become operational.
The second-generation satellites will gradually take over from the current first-generation satellites in the provision of Galileo services. At a future date, they will all constitute a complete constellation plus the necessary in-orbit spares.
ESA serves as the design, development and procurement agent for Galileo satellites on behalf of the European Commission, which funds the system overall.
