High-altitude pseudo-satellites (HAPS) are platforms that float or fly at high altitude like conventional aircraft but operate more like satellites. (Image: ESA Earth Observation Graphics Bureau)
The European Space Agency (ESA) is considering extending its activities to a new region of the sky via a novel type of aerial vehicle, a missing link between drones and satellites.
High-altitude pseudo-satellites, or HAPS, 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, offering continuous coverage of the territory below.
The best working altitude is about 20 kilometers, above the clouds and jet streams, and 10 kilometers above commercial airliners, where wind speeds are low enough for them to hold position for long periods.
From such a height they can survey the ground to the horizon 500 km away, variously enabling precise monitoring and surveillance, high-bandwidth communications or back up to existing satellite navigation services.
Several ESA directorates have teamed up to investigate their potential, explains future-systems specialist Antonio Ciccolella.
“For Earth observation, they could provide prolonged high-resolution coverage for priority regions, while for navigation and telecoms they could shrink blind spots in coverage and combine wide bandwidth with negligible signal delay,” Ciccolella said. “ESA is looking into how these various domains can be best brought together.”
“We’ve been looking into the concept for the last 20 years but now finally it’s becoming reality,” explained Earth observation specialist Thorsten Fehr. “That’s come about through the maturing of key technologies: miniaturised avionics, high-performance solar cells, lightweight batteries and harness, miniaturisation of Earth observation sensors and high-bandwidth communication links that can deliver competitively priced services.”
“There’s obvious potential for emergency response,” added Navigation engineer Roberto Prieto Cerdeira. “They could also be employed semi-permanently, perhaps extending satnav coverage into high, narrow valleys and cities.”
The QinetiQ-designed and Airbus-owned Zephyr-7 solar-powered unmanned aircraft holds the world flight endurance record at 14 days. (Photo: Airbus)
European companies have already unveiled product lines. For instance, Airbus has developed the winged, solar-powered Zephyr, which in 2010 achieved a world record 14 days of continuous flight without refuelling.
The Zephyr-S is designed to fly payloads of a few tens of kilograms for up to three months at a time, with secondary batteries employed to keep it powered and aloft overnight. A larger Zephyr-T version now in preparation will support larger payloads and power needs.
The first flight is projected for 2021 for Thales Alenia Space’s Stratobus airship. (Artist’s rendering: Thales Alenia Space/Briot)
Meanwhile, Thales Alenia Space is preparing the lighter-than-air Stratobus, with its first flight expected in 2021.
The buoyant Stratobus airship can carry up to 250 kilograms, its electric engines flying against the breeze to hold itself in position, relying on fuel cells at night.
Many other firms are also developing vehicles, payloads and services. Last month saw them gathered at ESA’s inaugural workshop, together with representatives of potential customers, including the European Defence Agency, Frontex — the European Union (EU) agency tasked with Europe’s border management — and EU Copernicus environmental monitoring services.
Airbus’s double-tailed Zephyr-T variant HAPS aircraft is designed to support larger payloads, keeping them aloft for months at a time. (Image: Airbus)
“This was the first meeting of its kind in Europe, with more than 200 HAPS experts,” said Juan Lizarraga Cubillos, from ESA’s telecoms area. “We heard from them on the needs, opportunities and critical issues within the field, particularly as a complement for existing satellite services, to start preparing a future ESA programme.”
ESA regards the vehicles as a valuable way of establishing applications that complement its satellites while also accelerating space technologies through early, high-altitude flight testing.
The point was also made that market acceptance of HAPS would come down to their efficiency and cost-effectiveness — and the best way to show that would be through demonstration projects.
“We have to fly them,” said Alvaro Rodriquez of EU’s Satellite Centre. “The technology is there, all the ingredients are there, now it’s time to mix them into a nice recipe.”
Thales Alenia Space’s Stratobus is topped with solar panels, powering its propellers to fly against the wind at 20 km for prolonged periods of service. (Image: Airbus)
Three of the four Galileo satellites 19-22 undergoing fit check with the dispenser that will support them during their Dec. 12 flight into orbit. (Photo: ESA)
Europe’s next four Galileo navigation satellites and the Ariane 5 rocket due to lift them into orbit are being readied for their Dec. 12 launch from Europe’s Spaceport in Kourou, French Guiana.
On Nov. 21, Galileo satellites 19–22 were declared ready for flight, along with their Ariane. Combined activities are now under way, culminating in the satellites meeting their rocket in the Final Assembly Building.
The satellites were flown in pairs to French Guiana last month. Once safely unboxed in the Spaceport’s cleanroom environment, they were tested to ensure they had suffered no damage during their transatlantic flights.
The four Galileo satellites mounted on top of a customised Ariane 5 rocket inside the aerodynamic fairing. (Image: ESA)
Next came their fit check, when they were mechanically and electrically linked one by one to the dispenser that will carry them during their ascent to the target 23,500 km-altitude orbit, before releasing them into space.
Last Friday saw the satellites filled with enough fuel to fine-tune their orbits and orientation during their projected 12-year working lives. Next, they will be attached to their dispenser together for the final time.
In parallel, their customised Ariane 5 is being assembled. Two solid-propellant boosters were mated with its main cryogenic stage before the addition of the interstage that carries the electronics to control the vehicle.
Next came the addition of the storable propellant stage, powered by a reignitable engine, which will deliver the quartet to their target orbit.
Once fully checked, the Ariane will be moved to the final building for the addition of the satellites atop their dispenser, sealed within their protective fairing.
This launch will bring the total Galileo constellation to 22, boosting the global availability of navigation signals. Galileo began Initial Services just under a year ago, the first step before full operations, on Dec. 15.
Galileo’s Ariane 5’s vehicle equipment bay is lowered for installation within the Final Assembly Building of Europe’s Spaceport in French Guiana. Flight VA240 carrying Galileo satellites 19–22 into orbit is scheduled for Dec. 12. (Photo: ESA)
Two more Galileo satellites have reached Europe’s Spaceport in French Guiana, joining the first pair of navigation satellites and the Ariane 5 rocket due to haul the quartet to orbit this December.
Inside the 747. (Photo: ESA)
Galileos 21 and 22 left Luxembourg Airport on a Boeing 747 cargo jet on the morning of Oct. 17, arriving at Cayenne-Félix Eboué Airport in French Guiana on the same day.
Resting within distinctive white air-conditioned containers, the satellites were driven to the cleanroom environment of the preparation building within the space centre.
Waiting for them there were Galileos 19 and 20, which arrived in September.
The four satellites will be launched together in mid-December by a customised Ariane 5, the elements of which reached French Guiana last month by sea.
Galileos 21 and 22 being unloaded from their 747 cargo aircraft at Cayenne – Félix Eboué Airport in French Guiana on Oct. 17. (Photo: ESA)
Galileo is Europe’s own satellite navigation system, providing an array of positioning, navigation and timing services to Europe and the world.
A further eight Galileo Batch 3 satellites were ordered last June, to supplement the 26 built so far.
With 18 satellites now in orbit, Galileo began initial services on Dec. 15, 2016, the first step towards full operations.
Further launches will continue to build the constellation, which will gradually improve performance and availability worldwide.
Q: What is the GNSS/PNT industry “Issue of the Year”?
Jose Angel Avila Rodriguez, signal and security implementation engineer, European Space Agency
A: The growth of PNT applications has been impressive and will continue. Assurance of PNT will thus gain an ever-increasing role, in both the security and the civil domains.
For GNSS, the key PNT contributor, there is in addition another challenge: its piece in the PNT cake will be contested by newcomers, such as telecom networks. Whether we will continue talking about A-GNSS or instead talk about Assisted 5G, with GNSS in that case taking on the role of signal of opportunity — that will depend on today’s decisions about future GNSS upgrades, the modernized versions of Galileo second generation, GPS III, and Beidou/Compass III, that will be flying around 2040.
Gyles Panther, president and CTO, Tallysman Wireless, Inc.
A: The key issues for PNT going forward, and into the indefinite future, are simply stated: availability and accuracy. Re-deployment of the eLoran infrastructure is a no-brainer. A potentially highly negative step would be the introduction of communication services within the mobile satellite L-band downlink frequency band (1525 MHz to 1559 MHz). Multi-constellational receivers track a much larger number of satellites and better disposed SVs (space vehicles) provide a lower horizontal DOP and hence greater accuracy.
Finally, GNSS needs to be defended against interference both intentional and accidental. Why on earth would we want to damage something that is providing so much utility to mankind?
Europe’s next two Galileo navigation satellites have touched down in Europe’s Spaceport in French Guiana ahead of the launch of a quartet by Ariane 5 at the end of this year (scheduled for Dec. 12).
Galileos 19 and 20 left Luxembourg Airport on a Boeing 747 cargo jet on the morning of Sept. 18, arriving at Cayenne — Félix Eboué Airport in French Guiana that evening.
Safely cocooned within protective air-conditioned containers, the pair were offloaded and driven to the cleanroom environment of the preparation building within the space centre.
A Galileo satellite in its protective container is unloaded from its cargo plane after landing in French Guiana Sept. 18. (Photo: ESA)
This building will remain their home as preparations for their launch proceeds, with the next two Galileos due to join them later this month.
The satellites join the first elements of their customised Ariane 5 at the centre — including its cryogenic main stage and half-shell payload fairing — which were delivered by ship the week before.
Galileo is Europe’s own satellite navigation system, providing an array of positioning, navigation and timing services to Europe and the world.
A further eight Galileo “Batch 3” satellites were ordered last June, to supplement the 26 built so far.
A Galileo satellite is driven to the Guiana Space Centre following its arrival on Sept. 18. (Photo: ESA)
With 18 satellites now in orbit, Galileo began initial services on Dec. 15, 2016, the first step towards full operations.
Further launches will continue to build the constellation, which will gradually improve performance and availability worldwide.
By Carmela Ruta, Francesco Paggi and Monica Gotta, Thales Alenia Space-Italia; D. Oskam, Airbus Defence and Space; and Rafael Lucas Rodriguez and Igor Stojkovic; European Space Agency / Presented at the European Navigation Conference, Switzerland, May 2017
The European Space Agency, Thales Alenia Space-Italy and Airbus Defence and Space contributed to the Search and Rescue/Galileo Forward Link system deployment and performance evaluation with a full-scale System Performance Validation test campaign, aimed at evaluating the performances of the SAR/Galileo system, in terms of distress detection rate, localization probability and localization accuracy.
Forward Link Message Detection probability in 10 minutes.
The paper describes SAR/Galileo principles and the COSPAS-SARSAT MEOSAR concept (detection and localisation of distress events based on MEO satellites). It presents the space and ground segments of the Galileo infrastructure that enables the SAR/Galileo Forward Link Service provision and the main inherent performances of the system. The SPV test campaign is described in terms of objectives and organization; the main results are presented, and the foreseen milestones for SAR/Galileo deployment are summarized.
Global availability of 5 km beacon localisation accuracy (95%) in 10 minutes.
Enclosed in its protective container, Galileo Full Operational Capability (FOC) Flight Model 21 (FM21) is seen departing ESA’s ESTEC Test Centre on Aug. 24. Photos courtesy of the European Space Agency
News from the European Space Agency
The last of 22 Galileo satellites has departed the European Space Agency’s (ESA) Test Centre in the Netherlands. This concludes the single longest and largest scale test campaign in the establishment’s history, ESA said.
Cocooned in a protective container for its journey — equipped with air conditioning, temperature control and shock absorbers — the final Galileo satellite left the establishment by lorry on Aug. 24.
ESA’s Test Centre at ESTEC in Noordwijk, the Netherlands, houses a collection of test equipment to simulate all aspects of spaceflight. It is operated for ESA by private company European Test Services (ETS) B.V.
In May 2013, the Test Centre began testing the first of 22 Galileo “Full Operational Capability” (FOC) satellites, having previously performed the same function for the very first Galileo “In-Orbit Validation” satellite under a separate contract.
Pictured is a Galileo Full Operational Capability satellite being removed from the Phenix thermal vacuum chamber after a fortnight-long “hot and cold” vacuum test.
The Galileo FOC satellites had their platforms built by OHB System AG in Germany, incorporating navigation payloads coming from Surrey Satellite Technology Ltd. in the United Kingdom. They then traveled on to ESTEC to be subjected to the equivalent vibration, acoustic noise, vacuum and temperature extremes that they will experience for real during their launch and orbit, plus testing of their radio systems.
With a steady stream of satellites coming off the production line, the challenge for the combined ETS and OHB team overseeing Galileo testing was to put them through all necessary tests on a rapid and efficient basis, while also keeping the Test Centre accessible to other European missions requiring its unique services.
A total of 14 FOC satellites have since joined the first four IOV satellites in orbit, forming an 18-strong constellation that began Initial Services to global users on Dec. 15, 2016. The next four FOC satellites are scheduled for launch on an Ariane on Dec. 5.
Europe’s Galileo navigation satellites orbit 23 222 km above Earth to provide positioning, navigation and timing information all across the globe.
“For the first time in more than four years, there are no Galileo satellites in the Test Centre, but hopefully this will not be the end of our association with the programme,” said Jörg Selle, managing director for ETS. “The contract for making the next eight Galileo satellites — known as Batch 3 — was also awarded to OHB last June, and ETS will be bidding for the contract to test these satellites too.”
“The availability of the ETS facilities in ESTEC have substantially contributed to the programme,” said Paul Verhoef, ESA director of the Galileo Programme and navigation-related activities. “We thank ETS for their professionalism and support over this extended period.”
The final Galileo travelled back to OHB in Germany for some final refurbishment ahead of its launch together with another three satellites in December.
Each Galileo satellite must go through a rigorous test campaign to assure its readiness for the violence of launch, the vacuum of space, and temperature extremes of Earth orbit, reported the European Space Agency.
Each one is despatched to a unique location in Europe to ensure its readiness before launch: a 3,000-square-meter cleanroom complex nestled in sandy dunes along the Dutch coast, filled with test equipment to simulate all aspects of spaceflight.
The test centre in Noordwijk — Europe’s largest satellite test site — is part of ESA’s main technical centre, but it is maintained and operated on a commercial basis on behalf of the Agency by a private company created for the purpose: European Test Services (ETS) B.V.
“Our company was founded 2000 as a joint venture between two of Europe’s leading satellite environmental test companies, Intespace in France and IABG in Germany,” said Pierre Destaing, ETS test programme support manager for Galileo. “That business setup is a source of flexibility: there are 30–35 people working here throughout the year, but if extra specialists are needed for a given campaign, we can call on our parent companies.”
ETS has been responsible for supporting many historic test campaigns – including space-certifying Europe’s 20-tonne ATV space truck and Envisat, the world’s largest civilian Earth-observing mission. But in terms of scale alone, its work with Galileo is the company’s greatest challenge.
ETS is about to complete its contracts with OHB System AG, covering the environmental test of 22 ‘Full Operational Capability’ Galileo satellites, preceded by the testing of the very first of the first-generation ‘In-Orbit Validation’ Galileo satellites on a previous, separate contract.
A Galileo FOC satellite is slid out of its transport container into the clean room at ESTEC. (Photo: ESA)
The pressure has been steady to ensure satellites are available in time to meet Galileo’s launch schedule.
“Traffic management is a big part of the job – it’s like a game of Tetris,” Pierre said. “We have a steady stream of Galileo satellites to accommodate, along with other missions such as the BepiColombo Mercury orbiter, Solar Orbiter, the Cheops exoplanet detector and currently the latest MetOp weather satellite, with a fixed set of test facilities. The biggest challenge is definitely ensuring that every project can have the access to the facility they need at the right time, which demands complicated logistics and security adherence.”
ETS has built up to a steady rhythm with the OHB System team, typically accommodating multiple satellites in storage on site, at the same time as others undergo further active testing.
“When each new satellite arrives, it is first unpacked within the carefully filtered and air conditioned Test Centre environment,” Pierre said.
Moving a Galileo Full Operational Capability satellite between test facilities at ESA’s Test Centre in Noordwijk, the Netherlands. (Photo: ESA)
The European Space Agency (ESA) and the U.S. National Aeronautics and Space Administration (NASA) are conducting a joint GPS/Galileo space receiver experiment onboard the International Space Station (ISS). This will be the first time that a combined GPS/Galileo receiver will operate in space.
The project aims to demonstrate the robustness of a combined GPS/Galileo waveform uploaded to NfASA hardware already operating in the challenging space environment: the Space Communications and Navigation (SCaN) software-defined radio testbed.
Testing activities include analysis of the GPS/Galileo signal and onboard position/velocity/time (PVT) performance; processing of code- and carrier-phase GPS/Galileo raw data for precise orbit determination (POD); and validating the added value of a space-borne dual-GNSS receiver compared to a single-system receiver under the same conditions.
This collaboration was initiated in 2014 and a Technical Understanding was signed in 2016.
Many new space applications may not be possible if constrained to using the limited signal availability associated with any single constellation of GNSS satellites.
This research therefore seeks to demonstrate the enhanced capabilities brought by the use of satellites from two or more GNSS constellations in the space domain. The net result will be more resilient space operations, greater mission flexibility, and enhanced PVT performance.
The project is currently in the testing and verification phase, and it is expected that the final implementation of the combined GPS/Galileo waveform on NASA’s SCaN Testbed on-board the ISS will be completed in September/October 2017, so that the initial operations of the first combined GPS/Galileo receiver in space can start in the October/November 2017 timeframe.
The researchers plan to present preliminary results at the UN International Committee on GNSS (ICG)-12 in Kyoto, Japan in December.
From ESA’s side, ESOC’s Navigation Support Office (NavSO) and ESTEC Experts for Radio Navigation Systems and Techniques (TEC-ESN) are involved in this project.
The overall project management from ESA’s side and POD aspects are covered by NavSO, and ESTEC’s Technical Directorate is in charge of the Galileo waveform development and implementation of the SW on the FPGA in cooperation with NASA. This activity is done with technical support from industry participants such as Qascom. Industry participation is a vital component as new markets for multi-GNSS receivers and complex space applications continue to emerge.
From NASA’s side, the project is sponsored by the Space Communications and Navigation (SCaN) Program within the Human Exploration and Operations Mission Directorate (HEOMD) at NASA Headquarters in Washington D.C. Integration and experimentation activities are being performed by the NASA Glenn Research Center.
NASA has initiated an international effort within the ICG to develop a fully interoperable multi-GNSS Space Service Volume (SSV), where a combination of constellation services will be available well above low-Earth orbit (LEO) to support newly emerging geostationary Earth orbit (GEO) and high-Earth orbit (HEO) missions — ranging from more precise station keeping to extend GEO belt capacity and maneuver recovery to enabling formation flyers and satellite servicing operations.
WERNER ENDERLE is head of Navigation Office, Ground Systems Engineering Department at the European Space Operations Centre of the European Space Agency.
JAMES J. MILLER is deputy director, Policy & Strategic Communications – Space Communications and Navigation in the Human Exploration and Operations Mission Directorate at NASA headquarters.
Anomalous GPS Signals from SVN49
By Fabio Dovis, Nicola Linty, Mattia Berardo, Calogero Cristodaro, Alex Minetto, Lam Nguyen Hong, Marco Pini, Gianluca Falco, Emanuela Falletti, Davide Margaria, Gianluca Marucco, Beatrice Motella, Mario Nicola and Micaela Troglia Gamba
Researchers at the Navigation Signal Analysis and Simulation (NavSAS) Group of the Politecnico di Torino detected in mid-May the presence of anomalous spikes in the L1 signal spectrum. The origin of the spikes was identified to be transmission of a non-standard code from a non-operational GPS satellite (GPS IIF-9, SVN49). Here we report on signal observations and address possible impacts on GNSS signal processing.
On May 17, 2017, during outdoor data collection, NavSAS researchers detected two spikes in the L1 spectrum, with sufficient power to be clearly visible on a display processing raw digital samples at the receiver’s intermediate frequency.
An initial check looked for a possible interfering source in the experimental set-up, since it was quite complex with multiple pieces of electronic equipment. The likelihood of this source was soon dispelled as the same kind of spectrum was visible on a spectrum analyzer (SA) connected to an active survey-grade GNSS antenna on the lab roof; results shown in FIGURE 1.
The spectrum is centered at 1575.42 MHz, with the SA set to a frequency span of 5 MHz. Connecting the SA to different survey-grade antennas on the roof, we found no remarkable differences. The spikes continued to appear on subsequent days, becoming clearly visible around 13:00 UTC and disappearing around 19:00 UTC.
Figure 1. L1 Spectrum of the received signal at 16:51 (Central European Summer Time; 14:51 UTC) on May 19, 2017, at the NavSAS Lab, Torino (located at 45°03’54.98767″ N, 7°39’32.28920″ E, 311.9667 meters).
Exclusion of Terrestrial Sources. The 24-hour repetition period of the phenomenon, along with the shape of the spectrum, could indicate the presence of a signal anomaly from a GNSS satellite. In a battery of tests, we probed the L1 spectrum in a wider area using assorted equipment.
For various reasons, we ended up focusing on a non-operational satellite: SVN49, launched March 24, 2009. We concluded that transmission of a non-standard code (NSC) from this satellite was the origin of the problem in the L1 spectrum.
Transmission of NSCs for testing purposes is foreseen in the GPS Interface Specification, IS-GPS-200. GPS satellites can switch off regular broadcasts of C/A code and P/Y code and transmit a non-standard C/A code and non-standard Y code.
Such operation is intended to protect users from receiving and utilizing erroneous satellite signals in case of unhealthy conditions on the spacecraft. Strictly speaking, this case cannot be formally considered as an “anomaly,” because the transmission of non-standard codes is documented in the IS-GPS-200.
Therefore, the transmission of an NSC can be considered a normal operation in itself, though it may reflect a problem with the transmitting satellite.
In this case the choice of the spreading sequence, which is likely a square wave, allowed the total power of the signal to be concentrated in just a few spectral components, thus originating continuous-wave-like in-band signals.
The distribution of the harmonics, the main components of which are at ±500 kHz, and the presence of the odd harmonics only, matches an earlier case in 2006 of a transmission of an NSC modulated as a binary-phase-shift-keying (BPSK) sequence with alternating logical 0s and 1s, transmitted at the C/A code chipping rate (Rc=1.023 megachips per second). The hypothesis of the BPSK with Rc=1.023 megachips per second spreading signal has been verified by simulation.
However, the NSC is designed to have negligible effect on tracking other healthy GPS satellite signals. Nonetheless, an NSC transmission can have a non-negligible impact in performance of user equipment.
When a GPS satellite is switched to NSC mode, a receiver immediately loses its capability to track that satellite signal. This is not the case with SVN49, as it is currently declared non-operational. However, due to the modified code sequence, a further effect is possible: the NSC introduces irregular components at a sustained level in the GPS signal spectrum.
According to Notice Advisory to Navstar Users (NANU) 2017001, SVN49 was broadcasting standard signals as PRN04 (though set unhealthy) since the beginning of the year; NANU 2017042 announced that PRN04 was to be re-allocated to SVN38 on May 18.
This switch matches the dates when we started to see the spikes, since, probably, SVN49 started that day to use the “square wave” for the spreading.
Implementing the square wave local code, it has been possible to successfully acquire and track the NSC.
The real-time software receiver N-Gene has been forced to acquire and track in real time the signal coming from SVN49. The receiver decoded the navigation message transmitted by SVN49, which exhibits a regular format, even if marked with an unhealthy flag.
Impact on Receiver Processing. Interference with harmonic components such as those generated by the use of a square wave could strongly impact a GNSS receiver in the acquisition and tracking blocks, because the interference power is dispersed over the whole search space by the correlation with the local code, compromising the acquisition accuracy and impacting other functional blocks.
The impact of interference spectral lines depends on their location within the frequency band. This is due to the almost periodic nature of the GNSS signals. The spectrum of a GNSS signal has components spaced at multiples of the inverse of the code period (for example, 1 kHz for GPS C/A code) with different power allocated to each component depending on the shape of the code spectrum.
The effect is larger in the case of matching of the interference spectral components with the ones of the GNSS signal. Furthermore, in this case, the strongest harmonics are close to the L1 carrier frequency and are not mitigated by the front-end filter since they fall within its narrow bandwidth.
The overall GNSS scenario has changed a lot recently. Galileo and BeiDou are also present, and Galileo signals, due to the different structure and code periods, have spectral lines spaced at 0.25 kHz. The frequency modulation of the interfering signal due to the variable Doppler shift is thus even more likely to hit some of the spectral components of these signals.
We are investigating further to assess the impact of the interfering signal from SVN49 on Galileo-based high accuracy applications.
U.S. Air Force Response
The 2nd Space Operations Squadron is performing maintenance on a presently non-operational satellite. SVN49 is broadcasting non-standard C/A and non-standard Y codes as described in IS-GPS-200. Space professionals continue to conduct safe and responsible command and control of the constellation to continue to provide accuracy that exceeds established system requirements.
As always, GPS users who experience issues should address them through the appropriate channels: military users should contact DSN 560-2541, commercial 719-567-2541 while civilian users should contact the U.S. Coast Guard Navigation Center at 703-313-5900.
Very Respectfully,
Nicholas J. Mercurio, Capt., USAF Director, 14th Air Force/JFCC SPACE Public Affairs
UK’s SSTL to build third batch of Galileo navigation payloads
News from the European Space Agency
Europe’s Galileo navigation constellation will gain an additional eight satellites, bringing it to completion, thanks to a contract signed at the Paris Air and Space Show.
The contract to build and test another eight Galileo satellites was awarded to a consortium led by prime contractor OHB, with Surrey Satellite Technology Ltd overseeing their navigation platforms.
This is the third such satellite signing: the first four In Orbit Validation satellites were built by a consortium led by Airbus Defence and Space, while production of the next 22 Full Operational Capability (FOC) satellites was led by OHB.
These new batch satellites are based on the already qualified design of the previous Galileo FOC satellites, except for changes on the unit level – such as improvements based on lessons learned and reacting to obsolescence of parts.
ESA’s Director of the Galileo Programme and Navigation-related Activities, Paul Verhoef, signed the contract with the CEO of OHB, Marco Fuchs and OHB Navigation Director Wolfgang Paetsch, in the presence of ESA Director General Jan Woerner and the EC’s Deputy Director-General for Internal Market, Industry, Entrepreneurship and SMEs, Pierre Delsaux.
“This procurement from OHB will enable the completion of the Galileo constellation and have reserves both in-orbit and on-ground,” said Director Verhoef. “This signing delivers the necessary infrastructure robustness that is essential for the provision of Galileo services worldwide.”
ESA signed the contract on behalf of the EU represented by the European Commission – Galileo’s owner. The Commission and ESA have a delegation agreement by which ESA acts as design and procurement agent on behalf of the Commission.
Signing Ceremony
Galileo is Europe’s own satellite navigation system, providing an array of positioning, navigation and timing services to Europe and the world.
With 18 satellites now in orbit, Galileo began Initial Services on Dec. 15, 2016, the first step towards full operational capability.
Further launches will continue to build the satellite constellation, which will gradually improve the system performance and availability worldwide. The launch by Ariane 5 of another four satellites is due to take place later this year.
The full Galileo constellation will consist of 24 operational satellites in three orbital planes plus orbital spares, intended to prevent any interruption in service.
These new eight satellites will provide the constellation with in-orbit and on-ground spares. ESA and the Commission are also in the process of developing an improved Galileo Second Generation for the next decade.
Galileo is now providing three service types, the availability of which will continue to be improved.
ESA’s Director of the Galileo Programme and Navigation-related Activities, Paul Verhoef (right), signing the contract of behalf of the European Commission, shakes hands with the CEO of OHB, Marco Fuchs beside OHB Navigation Director Wolfgang Paetsch, in the presence of ESA Director General Jan Woerner (in background) and the EC’s Deputy Director-General for Internal Market, Industry, Entrepreneurship and SMEs, Pierre Delsaux.
Galileo coverage
The Open Service is a free mass-market service for users with enabled chipsets in, for instance, smartphones and car navigation systems. Fully interoperable with GPS, combined coverage will deliver more accurate and reliable positioning for users.
Galileo’s Public Regulated Service is an encrypted, robust service for government-authorized users such as civil protection, fire brigades and the police.
The Search and Rescue Service is Europe’s contribution to the long-running Cospas–Sarsat international emergency beacon location. The time between someone locating a distress beacon when lost at sea or in the wilderness will be reduced from up to three hours to just 10 minutes, with its location determined to within 5 km, rather than the previous 10 km.
The public will begin benefiting as Galileo-capable devices enter the marketplace: 17 companies, representing more than 95% of global supply, now produce Galileo-ready chips.
SSTL continues Galileo work
“SSTL is delighted to have been selected to build the third batch of navigation payloads needed to complete the initial Galileo Constellation,” said Gary Lay, SSTL’s director of navigation. “I am confident that the OHB-SSTL solution offered the lowest risk and best value for money, and I believe that our selection as payload providers for the third time in succession demonstrates a high regard for our work.”
SSTL’s state-of-the-art Galileo FOC payload comprises different units including European sourced atomic clocks, navigation signal generators, high power traveling wave tube amplifiers and antennas. SSTL’s payload proposal for Batch 3 is for a recurrent build of the existing payload, with an evolution of the atomic clocks to incorporate advances made under the European GNSS Evolution Programme.
Fourteen of SSTL’s Galileo FOC navigation payloads are currently operational in orbit, with a further eight payloads already delivered to OHB for integration and test.
SSTL has been involved in the Galileo program since 2003 with the design and build of GIOVE-A, Galileo’s pathfinder mission. GIOVE-A was launched in 2005 and is still operational today, providing valuable data about the radiation environment in Medium Earth Orbit. An experimental GPS receiver on board GIOVE-A is also used to map out the antenna patterns of GPS satellites for use in planning navigation systems for future high altitude missions in Geostationary orbit, and beyond into deep space.
The invisible signals that Europe’s Galileo satellites are beaming down to the world are officially award-winning: the team behind their design has won the European Inventor Award, run by the European Patent Office, reports the European Space Agency.
Just like the Galileo satellites and their globe-spanning ground stations, the Galileo signals themselves needed to be designed, having to pack multiple Galileo services aimed at different classes of users within the limited frequency bands allocated for the system by the International Telecommunications Union.
This task was accomplished by the Galileo Signal Task Force, a multinational group of experts who came up with a pair of innovative signal modulation techniques.
This team was led by Spanish engineer José Ángel Ávila Rodríguez – now part of ESA’s Galileo team – and his French colleague Laurent Lestarquit from France’s CNES space agency, sharing in the European Patent Office’s European Inventor Award 2017.
The team also includes German Günter Hein, formerly head of the department studying the evolution of EGNOS and Galileo for ESA, as well as Belgian Engineer Lionel Ries, now in ESA’s technical directorate, as well as French CNES engineer Jean-Luc Issler.
“When the nations of Europe work together, the whole world benefits,” said José.
With 18 satellites now in orbit, Galileo began Initial Services on 15 December 2016, so the two signals the team devised are now everyday reality.
They took as their inspiration the GPS system, with signal shapes first designed back in the 1960s, but first fulfilling user needs today.
The first signal technique is called Alternative Binary Offset Carrier modulation, or ‘AltBOC’ for short, combining four separate signals into one large ones – resulting in the largest bandwidth navigation signal ever transmitted.
When used in its full performance AltBOC can support precision scientific applications such as geodetic measurements and seismic monitoring.
The second modulation method, called Composite Binary Offset Carrier or ‘CBOC’, results in a signal for use by the mass market, possessing both narrowband and wideband components.
The result is a signal that can work well with low-end receivers – such as those found in current smartphones – while the wideband component ‘future proofs’ the signal, allowing manufacturers to extend mass market receiver performance in the future.
The other goal CBOC had to match was to be interoperable with GPS signals, allowing receivers to use both sets of signals at once on a seamless basis.
With China planning to use a comparable CBOC-style solution for their Beidou satnav satellites, the resulting Galileo E1 Open Signal is set to become the new standard for mass market applications for the foreseeable future.
Two further satellites have formally become part of Europe’s Galileo satnav system, broadcasting timing and navigation signals worldwide while also picking up distress calls across the planet, reported the European Space Agency.
Liftoff of Ariane flight VA233, carrying four Galileo satellites, on Nov. 17, 2016.
These are the 15th and 16th satellites to join the network, two of the four Galileos that were launched together by Ariane 5 on Nov. 17, 2016, and the first additions to the working constellation since the start of Galileo Initial Services on December 15.
The growing number of Galileo users around the world will draw immediate benefit from the enhanced service availability and accuracy brought by these extra satellites.
The launch into space and the maneuvers to reach their final orbits still left a lot of rigorous testing before the satellites could join the operational constellation.
Their navigation and search and rescue payloads had to be switched on, checked and the performance of the different Galileo signals assessed methodically in relation to the rest of the worldwide system.
Galileo L-band antenna at ESA’s Redu ground station.
This lengthy testing saw the satellites being run from the second Galileo Control Centre in Oberpfaffenhofen, Germany, while their signals were assessed from ESA’s Redu centre in Belgium, with its specialized antennas.
The tests measured the accuracy and stability of the satellites’ atomic clocks – essential for the timing precision to within a billionth of a second as the basis of satellite navigation – as well as assessing the quality of the navigation signals.
Oberpfaffenhofen and Redu were linked for the entire campaign, allowing the team to compare Galileo signals with satellite telemetry in near-real time.
Making the tests even more complicated, the satellites were visible for only three to nine hours a day from each site.
The satellites are now broadcasting working navigation signals and are ready to relay any Cospas–Sarsat distress calls to regional emergency services.
Now that these two satellites are part of the constellation, the remaining pair from the Ariane 5 launch is similarly being checked to prepare them for service.
