Javier Benedicto, ESA’s Galileo Project Manager, looks on as Europe’s own satellite navigation system performs its historic first position fix of longitude, latitude and altitude. The position fix took place at the Navigation Laboratory at ESA’s technical heart ESTEC, in Noordwijk, the Netherlands on the morning of March 12, 2013, with an accuracy between 10 and 15 meters — expected taking into account the limited infrastructure deployed so far. Horizontal accuracy reached as high as 6 m. The left-side screen shows the position fix while the right side screen shows the position of the four Galileo satellites and their current signal coverage.
Did you get a fix on four Galileo satellites? Then there could be a certificate in it for you! ESA will recognize Galileo pioneers with commemorative certificates to the first 50 entities who document their achievement of a past or present fix. Details of how to apply are provided here.
To mark the first anniversary of Galileo’s historic first satnav positioning measurement, ESA plans to award certificates to groups who picked up signals from the four satellites in orbit to perform their own fixes.
In 2011 and 2012 the first four satellites were launched — the minimum number needed for navigation fixes.
Europe’s Galileo satnav system.
On March 12, 2013, Galileo’s space and ground elements came together for the first time to perform the historic first determination of a ground location — the Navigation Laboratory of ESA’s Technical Centre in Noordwijk, the Netherlands.
From this point, generation of navigation messages enabled full testing of the entire Galileo system — not just by ESA and its industry and institutional partners but also by any entity with a customized satnav receiver.
ESA’s Galileo team has heard about position fixes carried out by organizations and companies all over Europe and beyond, including as far away as Vietnam.
A year after the first fix, ESA is recognizing these Galileo pioneers with commemorative certificates to the first 50 entities who document their achievement of a past or present fix.
Applicants should send in their name, address, details of the receiver they used, the start and end time of their fixes in Universal Time Coordinated (UTC) and a plot of their latitude/longitude position fixes overlaid on a map, such as Google Earth. Submissions should be sent to [email protected] within the next two months. Certificates will be sent out after May 12, along with an online results update. See details of how to apply here.
The first Galileo services are scheduled to begin later this year, as more satellites are delivered into orbit. The next launches will occur in the second half of this year, each with two satellites aboard a Soyuz ST-B. They will take place in close succession to build up the constellation.
Many satnav receiver chips are already technically Galileo ready, requiring only software upgrades from their manufacturer to begin working with Galileo signals along with GPS and other international satnav systems.
Dual-frequency Galileo positioning performance during the In-Orbit Validation phase: positioning accuracy is an average 8 m horizontal and 9 m vertical (95% of the time). Its average timing accuracy is 10 nanoseconds on average. Plot courtesy of ESA.
Nucleus of Four Now Operational: It “Works, and Works Well”
Dual-frequency Galileo positioning performance during the In-Orbit Validation phase: positioning accuracy is an average 8 m horizontal and 9 m vertical (95% of the time). Its average timing accuracy is 10 nanoseconds on average. Plot courtesy of ESA.
“IOV was required to demonstrate that the future performance that we want to meet when the system is deployed is effectively reachable,” said Sylvain Loddo, ESA’s Galileo Ground Segment manager. “It was an intermediate step with a reduced part of the system to effectively give evidence that we are on track.”
Following a March 2013 first determination of a ground location, jointly by Galileo’s space and ground segments, program managers undertook a wide variety of tests all across Europe.
“More than 10,000 kilometers were driven by test vehicles in the process of picking up signals, along with pedestrian and fixed receiver testing. Many terabytes of IOV data were gathered in all,” said Marco Falcone, ESA’s Galileo System manager.
According to ESA’s elaboration on the test results, the system has proved itself capable of solely performing positioning fixes across the planet.
Galileo’s observed dual-frequency positioning accuracy is an average of 8 meters horizontal and 9 meters vertical, 95 percent of the time. Its average timing accuracy is 10 billionths of a second. Its performance is expected to improve as more satellites are launched and ground stations come on line.
For Galileo’s search-and-rescue function — operating as part of the existing international Cospas–Sarsat programme — 77 percent of simulated distress locations can be pinpointed within 2 kilometers, and 95 percent within 5 kilometers. All alerts are detected and forwarded to the Mission Control Centre within a minute and a half, compared to a design requirement of 10 minutes.
“Europe has proven with IOV that in terms of performance we are at a par with the best international systems of navigation in the world,” said Didier Faivre, ESA director of Galileo and Navigation-related Activities.
Historically Speaking. In a February 2013 GPS World article, Peter Steigenberger, Urs Hugentobler, and Oliver Montenbruck discussed Galileo-only positioning. “Using an ionosphere-free dual-frequency linear combination of pseudorange measurements on the Galileo E1 and E5a frequencies, the position of the TUME reference station [at the Technische Universität München (TUM) in Munich, Germany] could be determined with a 3D position error of less than 1.5 meters,’” the authors said.
Crystal Ball Gazing. The next two Galileo satellites, of the full operational capability (FOC) class, currently complete their testing for flight clearance at ESA’s ESTEC facility.
Six such satellites are destined to rise into space in 2014, according to ESA’s master plan. Should all those launches occur as scheduled, Galileo’s initial services could start by the end of the year.
GNSS Vulnerable: What to Do?
Too Much Sensitivity, Not Enough Robustness, Says Parkinson
Brad Parkinson, the founding architect of GPS, told a UK conference that the system needs to be made more robust to ensure worldwide availability of services to users. His concerns over GPS availability relate to threats such as the loss of authorized frequency spectrum (implicitly creating licensed jammers), space weather due to hyperactive ionospheric conditions, and deliberate or inadvertent jamming of GPS signals.
He warned that GPS is more vulnerable to sabotage or disruption than ever before, and charged that politicians and security chiefs are ignoring the risk. Western governments are “in their infancy in recognizing the problem,” he remarked further in an interview with London’s Financial Times. “[In the United States] I don’t know anyone that is really in charge of it. The Department of Homeland Security should be [but] … they don’t have any people that understand it very well. They’ve got one person without any budget to speak of.”
He also warned that Europe’s €5 billion Galileo system is equally at risk.
Parkinson proposed a three-stage program to:
Protect (legally) the signal and physically eliminate jamming sources;
Toughen the GPS/Galileo receiver’s resistance to interference;
Augment the GPS signals with other satellites or with ground-based transmitters such as eLoran.
To support his proposal, Parkinson stated, “The number one need for all GPS or Galileo users is availability. Over the years, manufacturers of signal receiver technologies have focused too much on sensitivity and not enough on resilience or robustness. The maritime industry is a particular concern where users have taken GPS for granted. They must increase preparedness and backups as they do in aviation or other GNSS-using industries.
“Even today, most ships have only GPS and the vision of their crew to guide them when approaching harbors. As you can see from today’s conference, there are a wealth of solutions to toughen and back up GPS, many of which are not technologically difficult nor expensive, but still their adoption in sectors such as global shipping is certainly not adequate.”
As part of his protection program, Parkinson urged that penalties for jamming GPS networks be coordinated worldwide. “In Australia, if you cause interference likely to cause prejudice to the safe conduct of a vessel, it’s five years in the jug [jail] and $850,000.” Contrasting this with a U.S. case that may simply impose a forfeiture of the culprit’s jamming device, Parkinson added, “I’m calling for the community of nations to move to the Aussie-type penalties.”
In the toughening regard, Parkinson alluded to integration of GPS data with information derived from an inertial positioning system. “If you combine all of these things, a good set should be able to fly within 1 kilometer of a jammer with a 10-kilometer range,” said Parkinson. “That’s what I call toughening.”
Parkinson made his remarks as the keynote speech at GNSS Vulnerabilities and Resilient PNT 2014, hosted by the Royal Institute of Navigation. He will also deliver the keynote address, “Assured PNT: Assured World Economic Benefits,” for the European Navigation Conference on April 15 in The Netherlands.
Russia will deploy as many as seven ground monitoring and augmentation stations for GLONASS outside its national boundaries. GLONASS/GNSS Forum Association Executive Director Vladimir Klimov stated that “It is planned to deploy about six or seven stations on foreign territories this year.” Negotiations for the stations are now taking place with foreign nations.
Currently, there are 46 GLONASS ground stations on Russian territory, eight in neighboring countries, three in Antarctica, and one in Brazil. The United States recently spurned, with some Congressional trumpeting, a Russian tender to site one of the ground stations on U.S. soil.
New Instrument in Space. In mid-February, the most recent GLONASS-M satellite traveled to the Plesetsk cosmodrome for a probable mid-March launch. GLONASS-M 54 will carry a high-accuracy thermal stabilization unit, installed on the spacecraft for testing and flight qualification. The next-generation K-class of GLONASS spacecraft will loft this device to provide increased positioning accuracy.
Five GLONASS-M craft are planned for launch in 2014, in one triple and two single launches.
The hounds of spring are on winter’s traces. As Galileo emerges from its long, cold slumber, the energy of a new constellation radiates through the skies to encourage blossoms across Europe. ESA’s recent declaration of in-orbit validation means the downstream satnav market can now truly get going.
If a lot of demand has yet to be demonstrated, certainly a lot of pioneer applications have been developed, and the pent-up current is about to flow. Witness a plethora of GNSS and geospatial conferences in March, April, May, and June, from Munich to Rotterdam to Geneva to London, and on to Prague. The presentations at these gatherings no longer lean so heavily on academic and technical projections and predictions, but embody real-world applications and actual products. Long awaited, Europe’s GNSS spring has finally sprung.
Brad Parkinson, the chief and original architect of GPS, fittingly kicked off the season this month in London, where he told a UK conference that GNSS needs to be made more robust to ensure worldwide availability of services to users. His concerns over signal availability relate to threats such as the loss of authorized frequency spectrum (implicitly creating licensed jammers), space weather due to hyperactive ionospheric conditions, and deliberate or inadvertent jamming of GNSS signals. Parkinson made his remarks as the keynote speech at GNSS Vulnerabilities and Resilient PNT 2014, hosted by the Royal Institute of Navigation.
Coming up soon, Dr. Parkinson will also deliver the keynote address for the European Navigation Conference on April 15 in the Netherlands — but more on that anon.
Munich Satellite Navigation Summit, Munich, March 25–27
The scene now shifts southward to Bavaria, where the long-running Munich Summit gathers government, financial, industrial, and scientific dignitaries for high-level perspective on all GNSS, certainly with a Galileo emphasis but prominently featuring GPS, GLONASS, BeiDou, QZSS, IRNSS, and SBAS.
The technical program of the Munich Satellite Navigation Summit includes a multitude of panel discussions involving invited speakers on further topics such as the legal issues of privacy devices and GNSS re-transmitters, achieving precise point positioning (PPP) on a global scale, the role of other autonomous sensors in future navigation, monitoring of climate and natural disasters, and integrated applications of GNSS and Earth observation.
The summit will also officially open the European Satellite Navigation and provide a parallel track on Copernicus, the European Commission´s Earth observation program.
GPS World’s contributing editor Tony Murfin will file a complete report on the Munich Summit in the inaugural issue of EAGER, the European GNSS and Earth Observation Report. Subscriptions are free to this new quarterly email newsletter at the preceding link.
EAGER will feature news of European industry, agency, and scientific developments in satellite-based positioning, navigation, and timing; geospatial technology; Earth observation from space; digital mapping; and location-based services. EAGER focuses on the EU programs Galileo, EGNOS, and Copernicus along with their applications, but also encompasses European involvement in the other GNSSs and their geospatial applications of all kinds. Knowledgeable reporting from European sources, and interviews with and articles by European GNSS/geospatial community leaders. The latest technologies, launch schedules, applications, equipment, and industry and policy developments.
ENC GNSS 2014, Rotterdam, April 14–17
More than 120 technical papers will be presented at the European Navigation Conference (ENC 2014), under the thematic header Technology, Innovation, Business. As previously mentioned, Bradford Parkinson will deliver one of the two keynotes on “Assured PNT – Assured World Economic Benefits,” joined on the podium by Prof. Erik Theunissen of Delft Technical University, speaking on “So You Think You Are Safe.”
The program continues with a Galileo session, in which ESA will present the latest results of Galileo IOV and future plans for FOC.
Preliminary meetings will be held by the European Maritime Radionavigation Forum (EMRF), the Resilient PNT Forum, EUGIN, IAIN, and European Journal of Navigation. On Tuesday, another kick-off (!!) of the European Satellite Navigation Competition (ESNC) 2014 will take place.
The Netherlands Institute of Navigation’s organizing committee chair Jac Spaans (also a long-time Editorial Advisory Board member of this magazine, and furthermore a knight in the Order of Orange-Nassau) is pleased to invite all satnav enthusiasts to the conference, taking place the week before Easter, allowing you to extend your stay and enjoy the tulip fields, the windmills, and other objects of interest in The Netherlands. Host-city Rotterdam, one of the biggest ports in the world, gives proof the Dutch saying, “In Rotterdam they do not sell shirts with long sleeves, because they roll them up anyway.”
Another of GPS World’s contributing editors, Don Jewell, will attend and report on the conference, either in his Defense PNT newsletter in May or as a guest columnist in this GNSS Design & Test newsletter of that month. To be sure, his column will also appear prominently in the second (June) issue of EAGER, the European GNSS and Earth Observation Report. Subscriptions are free to this new quarterly email newsletter at the preceding link.
Geospatial World Forum, Geneva, May 5–9
Now in its sixth edition, the Geospatial World Forum concentrates on geographic information systems (GIS) in mapping, remote sensing, satellite navigation as applied to the electricity sector and energy distribution; architecture, engineering, and construction; sustainable agricultural industrialization; smart cities, municipal management; disaster preparedness and coping, natural hazard monitoring; big data as a competitive business asset, business intelligence, and market analysis; multi-sensor integration for monitoring; geospatial’s role in healthcare; global peace and prosperity; and last but by no means least, in fact probably the most important in our long term, climate change.
Next up on our busy travel schedule — and nothing says an industry is growing like the launch of another new conference — comes GEO Business, primarily an exhibition but also conference featuring industrial training and demonstrations featuring the technology and services used by those working with spatial data.
GEO Business boasts that it was born out of consultation with key industry leaders, and as a result the show is organized in collaboration with the Chartered Institution of Civil Engineering Surveyors (ICES), the Royal Institution of Chartered Surveyors (RICS), The Survey Association (TSA), and the Association for Geographic Information (AGI). This is a joint cooperative event involving major players, both organizational and industrial, in the geospatial community.
Presentations will be given by Leica Geosystems (Mobile GIS), Esri UK, Carlson Software, Fugro (Advanced airborne survey), Trimble, GeoPlace (spatial addressing), Altus Positioning Systems (single- and dual-frequency data collection), Topcon (global-scope monitoring), Spectra Precision, Ordnance Survey (geospatial data management), iXBlue, and others.
By this point, I should start charging a subscription fee to anyone who has failed to sign up for EAGER.
European Space Solutions 2014, Prague, June 11–13
photo: European Space Solutions
Finally, the European Space Solutions conference in Prague has yet to be formally announced by the European GNSS Agency, but a pre-registration page is open.
The 2013 generation of this conference featured sessions on indoor location-based services and solutions, environmental protection, emergency response and disaster management, mobile applications, sustainable energy, road and traffic management, and the future of the Galileo Public Regulated Service, an encrypted navigation service designed to be more resistant to jamming, involuntary interference and spoofing, designated for authorized users.
Tim Reynolds, GPS World’s newest contributing editor, will likely report from Prague on this, as he will from several of the earlier spring shows. Based in Brussels for the last decade-plus, Tim will provide in-depth and up-close perspective on Galileo, Copernicus, and all things Europe connected with space and satellite navigation. His main public forum will be EAGER, the European GNSS and Earth Observation Report, but he will also furnish regular stories for the Navigate! e-newsletter and this one.
With the first Galileo services set to begin this year, the European Space Agency (ESA) is working directly with European manufacturers of mass-market satnav chips and receivers to ensure that their products are Galileo-ready.
“Our objective is to make sure, ahead of the European Union’s declaration of early Galileo services that mass-market devices are ready and able to make use of them,” explained Riccardo de Gaudenzi, head of ESA’s Radio Frequency Systems, Payload and Technology Division.
“In coordination with the European GNSS Agency, we put out an open call to satnav manufacturers offering testing with our laboratory facilities. We have gone on to work with five mass-market chipset makers and a comparable number of professional receivers manufacturers.”
Key facilities being used at ESA’s Navigation Laboratory include its state-of-the-art “hybrid localization solution rack,” where receiver chips can be plugged in. This rack generates simulated constellations of Galileo, GPS and other satnav systems along with Wi-Fi or mobile networks which phone-based satnav chips often additionally employ. It can also simulate inputs from the kind of inbuilt gyro-type devices receivers employ for dead reckoning, to continue positioning measurements when satellites are out of view.
Hybrid localization solution rack.
Another resource is the octobox — a mini anechoic chamber into which phones or mobile devices can be placed, to feed them simulated satnav and cellular network signals.
Octobox
Testing in the field is carried out with the Lab’s Telecommunications and Navigation Testbed Vehicle. This fully equipped van carries its own extremely accurate receivers to assess the performance of the consumer items being tested.
Whether they are being used for vehicle navigation, shipment navigation, or precision agriculture, the performance of satnav terminals comes down to the specialized chips embedded within them. The same is true of mobile phones, although their chips tend to be optimized for low-power, high-sensitivity operations.Post
Test vehicle.
“This is a very useful initiative from our point of view, closing the loop between Galileo and industry,” commented Philip Mattos of ST Microelectronics, whose Teseo-2 receiver chips are used in satnavs and embedded in cars.
“Thanks to earlier collaboration with ESA and the EU, the millions of multi-constellation satnav chips we sell annually have been equipped for Galileo signals since 2009. It will take only a software update to enable them to start using Galileo,” Mattos said. “We have worked a lot with simulated Galileo signals, but this cooperation is allowing us to optimize our software based on access to actual signals and background technical information.”
Combining radio frequency and silicon elements, a single 1-cm square chip can detect signals from multiple satellite constellations — Russia’s GLONASS and China’s BeiDou as well as Galileo and GPS — then convert them into precise positioning measurements.
Beamed across thousands of kilometers of space, the signals are incredibly faint, barely distinguishable from background noise. But a technique called correlation gain synchronizes them with copies of each satellite’s broadcast code stored in the chip’s memory to boost them to usable levels.
Data from other systems, such as in-car accelerometers or gyros, can also be fed into the positioning measurements as desired.
For mass-market single-frequency designs, an ESA-created ionospheric model allows the subtraction of ionospheric delays, its performance coming close to dual-signal standards.
Chips also apply stored ephemerides data embedded in satellite signals — updates on where satellites are positioned in the sky — to speed up acquisition times.
The first four Galileo satellites are already in orbit and operational. Over the course of 2014 six more satellites are planned to join them in three separate Soyuz launches. Galileo initial services are scheduled to start by the end of this year.
Switzerland has signed a cooperation agreement to participate in the Galileo and EGNOS programs, the pillars of the EU’s Global Navigation Satellite System (GNSS). Switzerland will now fully financially participate in the programs, and will retroactively contribute €80 million for the period 2008-2013.
The agreement, signed in Brussels December 18, 2013, also covers cooperation in areas such as security, export control, standards, certification and industrial cooperation.
The Swiss government is not a member of the European Union, but does hold membership in the European Space Agency (ESA). Norway, another ESA member who is not a member of the EU, signed a similar agreement with the commission in 2010.
Swiss authorities will pay an annual Galileo fee of €27 million to the commission for access to Galileo services, but access to the Public Regulated Service (PRS) signals is still being negotiated. PRS signals will be restricted to authorized users by governments for sensitive applications that require a high level of continuity.
“I welcome Switzerland’s decision to fully step on board the European space programme,” said European Commission Vice-President Antonio Tajani. “This co-operation will not only help to provide better results for the EU’s satellite navigation services, it will also open up a series of business opportunities for small and medium sized enterprises both from Switzerland and the EU.”
Through its membership of the European Space Agency (ESA), Switzerland has contributed to Galileo’s development phase. For example, the state-of-the-art hydrogen-maser clocks used by the Galileo satellites originate from Switzerland. Such extremely accurate clocks are crucial to a number of sectors. Wireless telecommunication networks use Galileo satellites’ timing signal for network management, for time tagging and for synchronization of frequency references. Certified time stamps are also necessary for applications such as electronic banking, e-commerce, stock transactions, quality assurance systems and services.
With the signing of this agreement Switzerland will now participate in the EU satellite navigation programs and in their committees and working groups.
Studies show that Galileo will deliver around €90 billion to the EU economy over the first 20 years of operation, while from now until 2020, the EU will spend €7 billion on satellite navigation. Switzerland’s financial contribution for the period 2014-2020 will be calculated in accordance with the standard formula1 applied for the Swiss participation in the EU research Framework Programme.
Artist’s concept of a GPS III satellite in orbit, courtesy of Lockheed Martin.
Air Force Orders GPS III Satellites 05 and 06 from Lockheed Martin
A December 12 contract modification provided Air Force funding to Lockheed Martin to complete the fifth and sixth GPS III space vehicles (SV 05-06). Lockheeed originally received funding to procure long-lead parts for satellites five through eight (SV 05-08) in February 2013.
The $200,700,415 cost-plus-incentive-fee modification (P00276) on an existing contract (FA8807-08-C-0010) for GPS III space vehicles 05 and 06 means that work will be performed at Littleton. Colorado and Clifton, New Jersey, and is expected to be completed by Dec. 14, 2017 for space vehicle 05 and June 14, 2018 for space vehicle 06. The Air Force Space and Missile Systems Center Contracting Directorate, Los Angeles Air Force Base, California, is the contracting activity.
Galileo Achieves First Airborne Tracking
The European Space Agency’s Galileo satellites have achieved their first aerial fix of longitude, latitude, and altitude, enabling the inflight tracking of a test aircraft.
ESA’s four Galileo satellites in orbit have supported months of positioning tests on the ground across Europe since the first fix in March. Now the first aerial tracking using Galileo has taken place, determining the position of an aircraft using only its own independent navigation system.
The milestone took place on a Fairchild Metro-II above Gilze-Rijen Air Force Base in the Netherlands on November 12. It was part of an aerial campaign overseen jointly by ESA and the National Aerospace Laboratory of the Netherlands, NLR, with the support of Eurocontrol, the European Organisation for the Safety of Air Navigation, and LVNL, the Dutch Air Navigation Service Provider.
A pair of Galileo test receivers was used aboard the aircraft, the same kind employed for Galileo testing in the field and in labs across Europe. They were connected to an aeronautical-certified triple-frequency Galileo-ready antenna mounted on top of the aircraft.
Tests were scheduled during periods when all four Galileo satellites were visible in the sky. The receivers fixed the plane’s position, as well as determining key variables such as the position, velocity, and timing accuracy; time to first fix; signal-to-noise ratio; range error; and range–rate error.
Testing covered both Galileo’s publicly available Open Service and the more precise, encrypted Public Regulated Service, whose availability is limited to governmental entities.
Flights covered all major phases: take off, straight and level flight with constant speed, orbit, straight and level flight with alternating speeds, turns with a maximum bank angle of 60 degrees, pull-ups and push-overs, approaches and landings.
The flights also allowed positioning to be carried out during a wide variety of conditions, such as vibrations, speeds up to 456 km/h, accelerations up to 2 ghorizontal and 0.5–1.5 gvertical, and rapid jerks. The maximum altitude reached during the flights was 3,000 meters.
GPS III Prototype Proves Constellation Compatibility
The Lockheed Martin prototype of the next-generation GPS satellite, the GPS III, has proven that it is backwardly compatible with the existing GPS satellite constellation in orbit.
During tests concluded on October 17, Lockheed Martin’s GPS III testbed successfully communicated via cross-links to Air Force simulators of the current GPS constellation in orbit. The current GPS constellation includes GPS IIR, GPS IIR-M, and GPS IIF satellites.
Testing also demonstrated the ability of an Air Force receiver to track navigation signals transmitted by the GPS III Nonflight Satellite Testbed (GNST). The GNST is a full-sized, functional satellite prototype at Cape Canaveral Air Force Station.
“These tests represent the first time when the GNST’s flight-like hardware has communicated with flight-like hardware from the rest of the GPS constellation and with a navigation receiver,” explained Paul Miller, Lockheed Martin’s director for GPS III Development. “This provides early confidence in the GPS III’s design to bring advanced capabilities to our nation, while also being backward-compatible.”
The first flight-ready GPS III satellite is expected to arrive at Cape Canaveral in 2014, for launch by the Air Force in 2015.
GPS III satellites will be the first GPS space vehicles with a new L1C civil signal designed to make it interoperable with other international global navigation satellite systems.
The GNST has helped to identify and resolve development issues prior to integration and test of the first GPS III flight space vehicle (SV 01). It has gone through the development, test, and production process for the GPS III program first, significantly reducing risk for the flight vehicles, improving production predictability, increasing mission assurance, and lowering overall program costs.
The GPS III team is led by the Global Positioning Systems Directorate at the U.S. Air Force Space and Missile Systems Center.
Lockheed Martin is the GPS III prime contractor, with teammates including ITT Exelis, General Dynamics, Infinity Systems Engineering, Honeywell, ATK, and other subcontractors.
Good News for Users and Manufacturers
The U.S. Air Force is directing transmission of continuous CNAV message-populated L2C and L5 signals starting in April 2014. The move is designed to help development of user equipment compatible with the civil signals. Full text of the CNAV memo appears below.
Galileo FOC Satellites Endure Simulated Space Tests
The European Space Agency’s newest Galileo satellite has emerged from five weeks of simulated space conditions. On November 29, a hatch slid open to end its thermal-vacuum test, a milestone on the way to orbit.
The satellite was placed in the 4.5-meter-diameter Phenix chamber in ESA’s ESTEC Test Centre in Noordwijk, the Netherlands, in late October. Once inside, the air was pumped out to create a space-quality vacuum. Temperature extremes were also reproduced, with the six copper walls of the thermal tent cooled by liquid nitrogen down to –180°C.
A second Galileo vehicle has been undergoing the same rigors at the site, along with a vibration and shock test to reproduce separation from the launcher. Thermal-vacuum testing on the second model will begin in early 2014. The two satellites will be launched on a Soyuz rocket from Europe’s Spaceport in French Guiana in mid-2014.
The next satellite is expected to arrive at ESTEC in March, with further satellites following every seven weeks or so. A total of 22 FOC satellites are being built by OHB in Germany, with navigation payloads being delivered from Surrey Satellite Technology Ltd. in the UK.
The first Galileo Full Operational Capability satellite emerges from the Phenix test chamber after five weeks of thermal–vacuum testing.
November 29, 2013, marks the 210th anniversary of the birth of Christian Doppler. His work laid down the fundamental concepts that enabled researchers at Johns Hopkins University in the United States to make observations on the signals of Sputnik I during the International Geophysical Year of 1957. From those observations more than 60 years ago, we can trace the development of GNSS as we know it today. The very genesis of GNSS drew on the combined science, technology, and innovation from Europe, the United States, and Russia. Today, GNSS is a truly global technology that has changed for the better the lives of an estimated one billion people.
2013 also saw a major milestone in the global history of GNSS with the announcement by the European Space Agency (ESA) that the Galileo system had generated its first position fix using operational space vehicles. Here at Trimble we have for some time been providing user equipment that is ready for the modernized, multiple-constellation environment emerging in the coming years. It is still exciting to see the plans of the GNSS operators gradually become a reality, whether it is the ongoing deployment of Galileo and BeiDou or the modernization of GPS and GLONASS. There is no doubt that GNSS users worldwide will benefit significantly from these new developments, and it is natural to expect that we will see continued user-driven adoption and integration of these systems in the year ahead, together with new applications and services that make full use of the expanding GNSS capabilities.
Global Addiction to Accuracy
We have come to expect — if not demand — that technologies continuously evolve to become faster, smaller, and more cost-effective, while also providing expanded functionality and benefits. For GNSS, this expectation includes increased accuracy and precision for a growing proportion of the total user base, together with a desire to determine location in more places or, ultimately, ubiquitously.
From a technological perspective, the trend to increased accuracy is moving beyond local or regional land- or satellite-based differential augmentation toward global networks and services. New technologies such as Trimble RTX use data from a global network of GNSS stations together with global connectivity and communications to facilitate precise point positioning without the need to connect to local or regional reference station networks. Such capabilities simplify the user’s experience with precise positioning, while at the same time vastly expanding the areas on Earth where such positioning can be quickly and conveniently carried out.
Over the past decades, high-precision GNSS positioning has been adopted by increasingly larger numbers of users in the context of end-to-end work-process solutions in industries from agriculture to construction, surveying and mapping, energy, mining, utilities, transportation, and government, to name but a few. With assets, workers, and work sites spread over large geographic areas, these industries and operations have transformed how their work is done through the use of systems that incorporate real-time location information. While we should expect adoption and advancement in these areas to continue due to the compelling economic, safety, and environmental benefits provided, we should also expect to see increasing adoption of high-precision GNSS positioning in new applications such as intelligent transportation and within some proportion of the consumer user base. Accuracy is, after all, addictive.
Availability, Too. Along with accuracy, availability of position is also proving to be addictive; once we come to depend on location-enabled systems in our professional and personal lives, our needs and expectations will naturally tend toward that of continuous availability at all times and regardless of location. Although new constellations with more satellites and new, stronger signals help in this regard, augmentation of GNSS plays a key role on the path to more robust ubiquity. From a Trimble perspective, many of our new product launches during the past year incorporated deep integration of multiple measurement technologies. New systems combine GNSS with inertial measurement units, gyros, tilt sensors, seismometers, optical measurement, imaging systems, lasers, and other sensors or technologies, all enabling location and movement determination (increasingly in three dimensions) of more objects in more places — including, in some cases, even inside buildings. Looking to the future,we can expect the appetite for ubiquitous positioning to continue unabated.
Multiple sensors are also used to collect non-geographic information. Increasingly, innovation is taking place at the intersection and aggregation of many different types of data, providing new insights and enabling more informed, more timely, and more insightful decisions across almost every facet of human activity. GNSS is rapidly expanding its role as an enabling technology in this regard. While we know that delivering consistently accurate positions is a decidedly nontrivial achievement, those positions are often just one component of increasingly large and complex endeavors. In fact, much of the innovation today lies in applications that enable new, more efficient approaches to work and enterprise management, and in the creation of new and powerful analytics from aggregated data.
Global Utility, Global Business
2013 marks another important anniversary: GPS officially reached Initial Operating Capability twenty years ago on December 8, 1993. In his 2011 State of the Union address, U.S. President Barack Obama cited GPS, along with the Internet, as key examples of how government-funded fundamental research can stimulate innovation and create whole new industries. The combination of those two technologies has transformed our lives in ways even the early visionaries may not have imagined. The U.S. government has contributed to the global success of GPS in ways beyond technological innovation. Following the 1983 Korean Airlines 007 disaster (caused in part by inaccurate navigation), President Reagan declared that GPS should be free and available to all, providing a stable policy foundation upon which successive U.S. administrations have continued to build, increasingly recognizing the importance of civilian GPS applications.
Importantly, the United States strengthened this open-access policy framework by publishing the Interface Control Document for GPS, which enabled entrepreneurs and innovators anywhere in the world to bring to life their ideas about how this new technology in space could be used on Earth. For the most part, other governments have followed U.S. leadership in announcing predictable policy access to worldwide satellite positioning and timing availability, allowing innovation to take place wherever it may. In the process it spawned a truly global industry.
Technology alone has not achieved the global impact of GNSS. Rather, it is the combination of technology, a transparent, stable policy environment conducive to global innovation and adoption, and the economics of a global market that together have led to so many people today enjoying the benefits that GNSS provides. Such alignment is equally important for the future: just as GNSS from the beginning built upon knowledge and achievement from around the world, its full international potential will be best realized through global, user-driven innovation, vibrant international entrepreneurship, and robust open markets. Given that we are still far from reaching that full potential, there is good reason for us all to have great expectations of GNSS operators, the industry, and the user community in 2014 and beyond.
Peter O. Large joined Trimble in 1996 and has served as a vice president and a member of the executive committee since 2010. He holds a BSc (Hons) in surveying and mapping science from the University of Newcastle upon Tyne, UK, and an M.S. in management from Stanford University.
By Marco Falcone, System Manager for the European Space Agency in the Galileo Project Office
Following the second Galileo launch in October 2012, leading to four operational satellites in orbit, a progressive chain of events has taken place in 2013 encompassing all Galileo Services, starting from the first position fix on March 12 (Figure 1), when navigation message continuous broadcast began.
Galileo System Time (GST) to Universal Time Coordinated (UTC) dissemination to timing users started on April 16 and since then has been maintained within 5 nanoseconds (Figure 2).
GPS to Galileo Time Offset (GGTO) dissemination started on April 22, favoring the use of our satellites for combined positioning with the GPS constellation. GGTO accuracy is well within 7 nanoseconds.
The first implementation of the Galileo Terrestrial Reference Frame (GTRF), aligned to the IGb08, an update of IGS08 (International Terrestrial Reference Frame 2008), has been available since May 27, including all deployed Galileo Sensor Stations sites.
The capability to disseminate Commercial Service data in the navigation message was demonstrated on June 25.
In July, several European Union Member States achieved the first position fix using Public Regulated Service (PRS) receivers as part of the EC-ESA joint PRS Participants To IOV (PPTI) campaigns, demonstrating PRS positioning and access control.
The first search-and-rescue (SAR) localizations using the operational mid-Earth orbit Local User Terminal (MEO LUT) in Maspalomas was exercised July 9, and the first dissemination of the acknowledgement via return link to users in distress was tested in October.
The majority of performance verification tests has been successfully completed as part of the In Orbit Validation (IOV) experimentation campaign completed at the end of October 2013, demonstrating the achievement of the Galileo system’s expected performance. The average positioning accuracy for E1/E5a dual-frequency Open Service users is already around 8 meters horizontally and 10 meters vertically. This is an impressive result considering the small number of Galileo satellites in orbit and the limited ground infrastructure so far.
Figure 1. Galileo first position fix (source: Timing and Geodesy Validation Facility).
But the single most important message from the In Orbit Validation campaign is that Galileo works, and it works well.
The experience gained and lessons learned during the IOV period, especially in the domain of ground operations, have been very useful and will be addressed as a priority in the next phase, as part of the planned new versions of the Ground Control Segment and Ground Mission Segment.
The launches in 2014 of the new FOC satellites manufactured by OHB will further increase the availability of positioning and timing accuracy to users.
Complementary system validation campaigns will be carried out next year, moving towards commercial receiver technology for all categories of users, with particular focus on the mass market and the Public Regulated Service. Following the letter issued by the European GNSS Agency to Galileo chipset manufacturers in July 2013, an opportunity has been given to interested companies to take part in a test campaign to support the early introduction of Galileo in commercially available receivers. The campaign will be carried out next year, focusing on the compatibility of the devices with the reception of Galileo Open Service signals and their combined use with GPS and GLONASS. A number of mass-market chipset manufacturers and professional receiver manufacturers have already expressed their interest in participating in the campaign.
Figure 2. GST and UTC prediction error (source: FOC WP1 System Engineering Technical Assistance).
Marco Falcone is system manager for the European Space Agency in the Galileo Project Office in Noordwijk, the Netherlands. He has been mission manager for the GIOVE-A and –B satellites, the precursors of the Galileo operational satellite constellation. Nowadays, his main task is to validate the overall Galileo system and to ensure that it fulfils in operations the required performance starting from the first four satellites of the In Orbit Validation Phase throughout the full deployment of the constellation. He received his Master’s degree in computer science from the University of Pisa, Italy and his Master’s degree in space systems engineering from the University of Delft, the Netherlands.
On August 30, QinetiQ and Rockwell Collins demonstrated the first joint satellite navigation positioning using live signals from the encrypted governmental services from the U.S. Department of Defense (DOD) GPS Precise Positioning Service (GPS-PPS) and the new European Galileo Public Regulated Service (PRS). The signals on GPS L1 and L2, together with Galileo PRS L1A and E6A, were processed and combined to form multi-frequency, multi-constellation position fixes.
Positioning, navigation and timing (PNT) services provided by GNSS, such as GPS and the forthcoming Galileo system, are essential to underpinning both commercial and economic activity (the EC estimates 6-7% of the developed world’s GDP) and the delivery of governmental responsibilities including the safety and security of citizens.
GNSS systems such as GPS and Galileo make use of very low power signals and are subject to inadvertent interference, deliberate jamming and spoofing (where an attacker generates a false signal masquerading as a valid one to mislead a user receiver). Attacks on GNSS may range from low-level criminal nuisance (a delivery driver stopping their employer tracking them), enabling theft of high-value vehicles fitted with trackers, through to state-sponsored attacks. This is potentially a significant concern for a wide range of governmental users including law enforcement, security and emergency services, critical national infrastructure, transport and defense users. The use of multiple independent, secured navigation services provides significant improvements to navigation robustness and, along with other measures, offers substantial counters to these threats.
“This has been our first opportunity to explore how secured navigation services on GPS and Galileo can be used together to provide users with critical reliance on PNT with robust and continuous navigation services,” Nigel Davies, Head of QinetiQ’s Secured Navigation Group said. “QinetiQ is proud to be a key, long-term contributor to the Galileo Programme, having been working closely with the European Space Agency (ESA), the European GNSS Agency (GSA), European industrial partners and European Member States since 2003. QinetiQ and Rockwell Collins wish to thank ESA, the EC and GSA for support in accessing Galileo, as well as the UK Space Agency, UK Satellite Applications Catapult and the UK MOD for their support.”
Delta IV, the current GPS launch vehicle, awaits a date with space at Cape Canaveral.
Launch Delays Ground GPS IIF and Galileo FOC
The scheduled October 23 launch of GPS IIF-5, the fifth in the current “follow-on” generation of GPS satellites, has been postponed in order to complete a review of an adjustment made to the rocket’s upper stage engine. A loss of thrust by a Delta IV rocket upper stage during a GPS launch last year worried the Air Force and the United Launch Alliance (ULA), though the satellite successfully reached its intended orbit.
A subsequent investigation identified a fuel leak in the engine system as the culprit. Two medium Delta IV rockets and one heavy version have launched since then, but ULA said further investigation had produced new information about the engine’s first start.
While no new launch date has been set, the ULA released a statement:
“The ongoing Phase II investigation has included extremely detailed characterization and reconstructions of the instrumentation signatures obtained from the October 2012 launch and these have recently resulted in some updated conclusions related to dynamic responses that occurred on the engine system during the first engine start event.
“The GPS IIF-5 Delta IV launch is being delayed to allow the technical team time to further assess these updated conclusions and improvements already implemented and determine whether additional changes are required prior to the next Delta IV launch.
“The Delta IV booster for the GPS IIF-5 mission has completed the standard processing and checkout on the launch pad and will be maintained in a ready state for spacecraft mate and launch pending completion of this assessment. A new launch date will be established when the assessment of the updated dynamic response information is completed in the coming weeks.”
A Soyuz rocket (right) will carry Galileo FOC satellites, but no sooner than June 2014.
Galileo. Continuing delays in ground testing of the first two fully operational Galileo satellites have postponed their launch to June 2014 at the earliest.
According to European officials, the European Space Research and Technology Centre (ESTEC) thermal vacuum chamber for testing satellites under orbit conditions was not ready for the two FOC satellites delivered by OHB in late summer.
The satellites thus cannot ship to the Guiana spaceport in South America in time for a planned 2013 launch on a Soyuz rocket. The Galileo schedule is also running into bottlenecks with scheduled launches by other satellite programs aboard Guiana Soyuzes.
A six-week test of the first Galileo satellite at ESTEC reportedly got under way in October.
Svalbard station on Spitsbergen in the Norwegian Arctic.
Ground Network Supports Galileo for SAR
Completion of a pair of European Space Agency dedicated ground stations at opposite ends of that continent has enabled Galileo satellites in orbit to participate in global testing of the Cospas–Sarsat search and rescue system.
The Maspalomas station, in mid-Atlantic Canary Islands, was activated in June. In September, the Svalbard site on Spitsbergen in the Norwegian Arctic activated. The two sites can now communicate and will soon undertake joint tests.
The International Cospas-Sarsat Programme is a satellite-based search and rescue (SAR) distress alert detection and information distribution system, established by Canada, France, Russia, and the United States, with participation by 33 other countries.
Activation of the two new stations enables participation of the latest two Galileo satellites in a worldwide test campaign for Cospas-Sarsat expansion.
The program is introducing a new medium-orbit SAR system to improve coverage and response times, with the Galileo satellites in the vanguard.
The second pair of Europe’s Galileo satellites — launched together in October 2012 — are the first of the constellation to host SAR payloads. These can pick up UHF signals from emergency beacons aboard ships or aircraft or carried by individuals, which are then relayed to ground stations. There, the source is pinpointed and automatically passed on to a control center, which then routes it to local authorities for rescue.
“The Galileo satellites, tested in combination with the same SAR payloads on Russian GLONASS satellites as well as compatible repeaters on a pair of U.S. GPS satellites, showed an ability to pinpoint simulated emergency beacons down to an accuracy of 2–5 kilometers in a matter of minutes,” explained Igor Stojkovic, ESA Galileo SAR engineer.
“Our in-orbit validation tests so far have been in line with expectation and beyond, giving us a lot of confidence in the performance of the final system, once completed. And using a combination of satellites is just how the upgraded system will operate in practice, in order to localize distress signals.”
Localization test performed from Maspalomas MEOLUT as part of Galileo’s SAR in-orbit validation. Beacon locations obtained with four satellites are shown in black, while those using three satellites are shown in grey. More than 93 percent of all beacon locations, after only a single beacon burst has been received, are within the required five kilometers from actual beacon position.
System Briefs
GLONASS Seeks UK Ground. According to the website of the Russian magazine GLONASS Messenger, the Russian Federal Space Agency communicated its proposals for specific areas in the United Kingdom (or, more likely, its territories) to accommodate stations of the GLONASS System for Differential Correction and Monitoring (SDCM). Apparently, an offer was made by the deputy head of Roscosmos, Oleg Frolov, in discussions with David Parker, the director of the British Space Agency. The desired locations for the stations will not be disclosed until the approval of their establishment by the British side, the website reported.
Head Rolls. After repeated satellite launch failures and rumblings about embezzlement and corruption within the Russian space program Roscosmos, Vladimir Popovkin was let go as director and replaced by Oleg Ostapenko, a colonel general in the Russian Military, deputy minister of Defence, and former commander of the Aerospace Defence Forces. The Russian government also announced formation of new agency, the United Rocket and Space Corporation, to manage satellite and rocket manufacturing facilities heretofore supervised by Roscosmos.
Navigation Support Office Provides Services for IGS and Users
By Werner Enderle, Loukis Agrotis, Rene Zandbergen, Mark van Kints, and Jens Martin
The European Space Operations Centre has taken on the roles of real-time analysis center, data provider, and analysis-center coordinator for the International GNSS Service’s Real-Time Service, providing a number of products combining data streams from multiple sources.
The Navigation Support Office of the European Space Agency’s Space Operations Centre (ESA/ESOC) in Darmstadt, Germany, has for the last decade been involved in activities related to the provision of real-time GNSS augmentation services. The motivation for these activities is to support a number of ESA objectives, including:
Orbit determination support for low-Earth orbit missions using GNSS;
Development and validation of operational capabilities, with an emphasis on Galileo;
GNSS infrastructure development, including advanced techniques for better exploitation of the European GNSSs, Galileo, and EGNOS;
Research, development, and support to European industry through technology transfer.
The concept adopted is the generation of precise GNSS orbits using state-of-the-art batch orbit-estimation software. The predicted orbits, accurate to a few centimeters, are used in a Kalman filter, operating in real time, to estimate precise corrections to the satellite clocks from GNSS observations received from a global real-time receiver network. The orbit and clock products can then be made available to users with a latency of 3–4 seconds from the observation epoch.
The software architecture is modeled after concepts used in satellite control centers with the real-time observation and product streams treated in the same way as satellite telemetry data. A concept of circular history files has been developed, combining seamless real-time processing and retrieval capabilities with the ability to archive data for historical playback. Extensive display and visualization capabilities are also available.
Participation in the International GNSS Service (IGS) Real-Time Pilot Project has enabled validation of the ESOC software, with continuous operation and monitoring of two solution chains, starting in 2008. As the IGS Real-Time Analysis Center coordinator, ESOC has developed and operates a real-time combination solution, combining streams from multiple sources, as an offering of the IGS Real-Time Service, formally launched in April 2013.
GNSS Infrastructure
The ESOC software infrastructure modeled after real-time satellite control systems includes many of the elements for data processing, archiving, and visualization that are common to such systems. In particular, it implements a specially designed circular filing system for streaming data, allowing maintenance-free operations for processing and archiving of data and products, and seamless transitions from historical to live data processing. Additionally, it includes a highly sophisticated job scheduler for automating operations and an integrated events and alarms monitoring system.
The software subsystems belong to one of three functional categories:
Infrastructure. Software is written in C++. The main components are middleware elements for history filing and event logging and a job scheduling application. All middleware elements have C++, Java, and FORTRAN interfaces.
Algorithmic. Software is written in FORTRAN 90, C++ or Java. It incorporates applications for real-time and batch data processing and estimation and for generation of products and comparison statistics between results sets.
Visualization. Software is entirely written in Java for portability. It includes real-time graphical and alphanumeric display applications and the graphical user interface.
Figure 1 shows the integrated desktop that provides all the functions for software configuration, monitoring, and control. Also shown are examples of graphical and alphanumeric displays. The integrated desktop combines the job scheduler display (left side) with the events display (right), allowing the operator to easily monitor the status of all running batch and real-time applications.
Figure 1. Real-time processing desktop and sample displays.
The job scheduler is configured to submit all batch jobs at pre-defined times or intervals, and to monitor the real-time applications. The batch orbit determination function is typically executed every two hours and includes jobs for screening and processing observations from up to 80 stations. The predicted orbits from these runs are updated to provide the most recent information to the real-time estimation.
The job scheduler also acts as a watchdog to ensure that all real-time processes (resident tasks) are continuously running. Any abnormal termination is detected, and the relevant task is restarted automatically. This can also guard against hardware failures, because tasks can be configured to run on more than one hardware node and will be restarted on a backup node if the prime fails.
Resident tasks are used for processing and filing observation and broadcast ephemeris messages and for performing the real-time estimation. The real-time estimation processes phase and pseudorange observations arriving at the rate of 1 Hz and screens the data to detect outliers and cycle slips. It uses a Kalman filter to estimate multi-GNSS satellite and receiver clock corrections, tropospheric zenith delays at each observing site, and phase biases for each satellite-receiver link. The estimation interval is user-configurable and is currently set at 5 seconds. The estimated satellite clock corrections and predicted orbit information are sent to an output stream and disseminated to users in the form of RTCM SSR messages.
The software capabilities were originally designed to support the GPS constellation. These capabilities have now been extended to support all the available GNSS constellations, with emphasis on Galileo. In addition to multi-constellation, the capability of multi-frequency processing has been added.
A network status monitoring display in the form of a world map (see Figure 2) gives the operator an overview of the network data flow. Station and satellite icons are color-coded to reflect the health of the live data links. It is also possible to see the number of live links to each station or from each satellite and the data latency and percentage availability of the observations from each station.
Figure 2. GNSS network status monitoring display (GPS-only).
To supplement the investment in software, ESOC has maintained and expanded the capabilities of its receiver network. This takes advantage of the existence of a number of ESA-operated satellite tracking sites with the necessary infrastructure (power, communications, atomic frequency standards, concrete pillar for mounting of the GNSS antennas) to host GNSS equipment with minimal additional operating costs. All ESA sites are now equipped with multi-GNSS capability receivers and associated antennas. Additional sites are also being procured with the objective of creating an independent network of around 30 sites with global coverage.
Real-Time Activities, Projects
The investment in GNSS software, equipment, and infrastructure has enabled ESA to participate in a number of projects with institutional and commercial partners.
As a major contributor to the IGS, ESOC has been a strong supporter of the IGS Real-Time Pilot Project. Since the original call for participation, and through to the establishment of the recently launched (April 2013) IGS Real-Time Service (RTS), ESA has played a leading role by assuming the roles of real-time analysis center, data provider, and analysis-center coordinator. In the latter role, ESOC is responsible for the generation of the RTS products and has been generating and disseminating IGS real-time combination streams after processing the real-time solutions from up to 10 analysis centers. Included in these solutions are two streams generated by the ESOC Real-Time Analysis Center. One of these uses orbit information generated by the NAPEOS software (ESOC’s Navigation Support Office standard software package for precise orbit determination), which provides orbit updates every 2 hours. The second ESOC solution stream uses the IGS rapid orbit product, which is updated every 6 hours.
Stemming from the recognition that real-time services rely on the development of standards and data formats, ESOC has been instrumental in aligning the interests of the IGS community with those of the Radio Technical Commission for Maritime Services (RTCM). ESOC, along with NRCan, represents the IGS at RTCM meetings. Over the last 4–5 years, this forum, which brings together GNSS service providers, users, and receiver manufacturers, has made significant progress in agreeing on standards for:
real-time orbit and clock correction messages in state space representation (SSR) format;
new multi-GNSS standards for real-time high-precision observations and for broadcast ephemeris dissemination.
ESOC also represents the RTCM at the Galileo Geodetic Reference Interface Working Group, a group of experts advising the EC on exploitation of Galileo services for the geodetic community.
In its mandate to assist European industry, ESOC has been working with Fugro for software development related to the implementation of high-precision augmentation services. The Fugro G2 service, providing augmentation products for GPS and GLONASS, uses software developed by ESA and has been operational since early 2009. The service is being extended to include Galileo, with successful trials already demonstrated by Fugro.
Capabilities and Performance
In terms of the IGS RTS, Figure 3 shows the performance of the combination solution produced by ESOC from the results of the contributing analysis centers. The plots show daily clock standard deviations and 1-D RMS orbit differences between the combination solution and the IGS rapid solution. It can be seen that the clock results are of the order of 0.1 nanosecond and the orbit differences at the level of 30–40 millimeters. The advantage of the combination is the ability to identify and eliminate outliers, by examining the differences between the contributing analysis-center solutions. It can be seen that the outliers affecting the early results have been eliminated, with very stable results since around GPS week 1650.
Figure 3. Real-time service orbit and clock comparisons against IGS rapid products.
The monitoring of the RTS clock solutions in the precise point positioning (PPP) domain is performed by BKG. Figure 4 shows the kinematic PPP performance of one of the ESOC solutions over an interval of 24 hours. It can be seen that accuracies at the decimeter level can be achieved.
Figure 4. Example of kinematic PPP performance of ESOC solution.
To highlight the importance of combining computational and visualization capabilities, the plot in Figure 5 shows the estimated satellite clock behavior of GPS satellite G01. Since the middle of January 2013, the satellite clock started exhibiting a series of clock jumps with a magnitude of 3 nanoseconds. This pattern was observed once per orbit, with clock jump events every 12 hours. The problem was resolved on February 6, with the satellite being taken out of service and reconfigured. The ESOC capabilities allow for the detection and monitoring of such events in real time, creating the possibilities for a timely response (for example, by suppressing the problematic satellite) to ensure the service is not degraded.
Figure 5. GPS PRN-1 anomalous clock behavior.
The software visualization capabilities also allow the possibility to identify and visualize signal problems with the satellites. In the example in Figure 6, GPS satellite G30 is seen to be tracked by 14 receivers at 19:43:19 on April 11, 2009. The live links are identified by the light blue lines radiating from the satellite. In the next snapshot, at 19:44:35, all 14 receivers appear to have lost the measurements from this satellite, as the grey lines indicate geometric visibility but no measurements arriving at the stations. At the same times, the receivers are continuing to track other satellites. This behavior has been observed a number of times and is known to affect only the Block IIA range of GPS satellites. A loss of measurements for a period of 1–2 minutes is typically observed.
Figure 6. Signal drop from Block IIA GPS satellite.
Conclusions
The latest improvements of ESOC’s Navigation Support Office software provide full multi-frequency and multi-constellation processing capability. The IGS Real-Time Service is provided as a routine operational service since April 2013, enabling a kinematic precise point position solution at accuracy levels in the 10–20 centimeter range. Existing ESOC real-time capabilities are also ready for potential use within Galileo.
Acknowledgements
ESOC is working with a large number of partners and real-time analysis centers. In particular we would like to thank BKG, NRCan, GFZ, CNES, DLR, GMV, JPL, IGS Governing Board, Fugro, GEO++, TUW, WHU, Geoscience Australia, NGS, UPC.
Werner Enderle is the head of the Navigation Support Office at ESA\ESOC. Previously, he worked at the European GNSS Authority and for the European Commission, in charge of the procurement for the Galileo Ground Control Segment. He holds a doctoral degree in aerospace engineering from the Technical University of Berlin, Germany.
Loukis Agrotis, with his company Symban, is a contractor for ESA working on the development of ESOC’s Real-Time GNSS infrastructure. He is also the Analysis Centre Coordinator for the IGS Real-Time Pilot Project and represents the IGS at the Radio Technical Commission for Maritime Services (RTCM). He holds a Ph.D. in satellite orbits and the Global Positioning System from the University of Nottingham, UK.
René Zandbergen is a navigation engineer in ESA’s Navigation Support Office, based at ESOC in Darmstadt, Germany. He is involved in running operational activities related to high-precision and high-availability navigation support services in near-real time and real time. He holds a Ph.D. in satellite altimeter data processing from the Delft University of Technology in the Netherlands.
Raytheon Company reached several milestones recently in its development of the GPS Next -Generation Operational Control System (GPS OCX). Lockheed Martin’s GPS III Non-flight Satellite Testbed (GNST) — a full-sized, functional satellite prototype currently residing at Cape Canaveral Air Force Station — successfully established remote connectivity and communicated with OCX during pre-flight tests.
GNST proved that it could connect with and receive commands from Raytheon’s Launch and Check Out System (LCS), a part of OCX that supports the satellite and mitigates risks prior to launch. The GNST received commands from Lockheed Martin’s Launch and Checkout Capability (LCC) node in Newtown, Pennsylvania via the OCX servers at Raytheon’s facility in Aurora, Colorado; the system then returned satellite telemetry to the control station. The tests mirror launch and early orbit testing planned for all flight vehicles.
“While we have connected OCX with ground-based simulators before, these tests were the first time that OCX and a GPS III satellite have actually communicated,” said Keoki Jackson, vice president for Lockheed Martin’s Navigation Systems mission area.
Ahead of Schedule. Raytheon received Interim Authorization to Test (IATT) security certification from the U.S. Air Force for OCX LCS four months ahead of schedule. The company received a one-year certification with no liens, meaning the government does not require any changes.
“Typically, IATT certification is given for six-month increments,” said Matthew Gilligan, Raytheon’s GPS OCX program manager and a vice president in Raytheon’s Intelligence, Information, and Services business. “The LCS one-year accreditation speaks to the quality of the information assurance design and threat protection.” The IATT not only includes the LCS, but also Lockheed Martin’s GPS III satellite support systems, Exercise and Rehearsal Training Tool, and Upload Generation Tool.
OCX is being developed in two blocks. There are seven iterations in Block 1 and one in Block 2. LCS is the fifth Iteration of Block 1; it successfully completed Critical Design Review in June 2013.
Early Orbit Exercises. Lockheed Martin and Raytheon also completed the third of five planned launch and early orbit exercises to demonstrate launch readiness of GPS III and OCX.
Exercise 3 demonstrated space-ground communications; first acquisition and transfer orbit sequences; orbit-raising maneuver planning and execution; and basic anomaly detection and resolution capabilities. In addition, the industry and Air Force GPS Directorate teams jointly executed mission planning activities, such as orbit determination and the generation of upload command files.
Two additional readiness exercises and six 24/7 launch rehearsals are planned before launch of the first GPS III satellite. The first flight GPS III space vehicle (SV-01) is expected to be available for launch in 2014, and launched by the U.S. Air Force in 2015.
Exelis Encryptors. Exelis delivered the first three of a planned 14 ground-based encryptors to Raytheon Company for OCX. Designed to automatically code and decode GPS signals, encryptors facilitate the exchange of user information by securely transmitting navigation payload data between the OCX ground station and the orbiting constellation of satellites.
Delivery followed successful thermal, electromagnetic interference and security verification testing. Exelis provides critical elements of software in the navigation processing subsystem that will enable controllers to better understand the exact position of GPS satellites. This helps ensure accurate navigation information is securely broadcast to users. In addition to encryptors, Exelis is building high-precision receivers for use in GPS ground monitoring stations and satellite signal simulators for testing purposes.
Exelis is also on contract with Lockheed Martin to provide the payloads for the GPS III satellites.
Europe Tests Galileo Public Regulated Service
European Union member states began their independent testing of the Public Regulated Service (PRS) broadcast by the four Galileo navigation satellites in orbit. Transmitted on two frequency bands with enhanced protection, PRS offers a highly accurate positioning and timing service, with access strictly restricted to authorized users, such as government defense, security, and emergency services.
PRS access was initially considered for Galileo’s Full Operational Capability phase, but it has been enabled in 2013 in response to the strong interest of member states in this service. To allow early access to PRS during the current phase, the European Commission and ESA began the joint project PRS Participants To IOV (PPTI) in July 2012.
ESA ensured the availability of several tools developed under ESA contracts, including test receivers and other qualification equipment. ESA’s PRS Laboratory, based at the Agency’s ESTEC technical centre in Noordwijk, the Netherlands, provided training, demonstrations and sample data.
“Belgium, France, Italy, and the UK have now performed independent PRS acquisition and positioning tests. In parallel, ESA, through collaboration with Dutch and Italian authorities, is conducting PRS fixed and mobile validation in several locations in the Netherlands and Italy,” said Miguel Manteiga Bautista, head of ESA’s Galileo Security Office.
The PRS tests have demonstrated a current autonomous positioning accuracy of less than 10 meters when in the correct geometrical configuration. This is an impressive result considering the small number of Galileo satellites in orbit and the limited ground infrastructure so far deployed.
Italy has developed its own PRS receiver, and tests have confirmed the feasibility of independent PRS receiver development and verification based on specifications provided by ESA.
“The PPTI project is still ongoing to test more advanced functionalities this coming autumn and to run the first aeronautical PRS tests in collaboration with the Dutch authorities. Other member states have also expressed their willingness to join the IOV PRS experimentation campaigns soon,“ concluded Miguel Manteiga.
The project is a first step to ensure use of the PRS as soon as it becomes operational. It will be complemented by PRS pilot projects, focused on PRS applications, which are currently under definition in a common effort between European agencies.
The United States has submitted a request to be able to use Galileo’s PRS. Other non-EU countries have also expressed a desire to be associated with the program.
System Briefs
Way to Go GAO, Part II. The Air Force should come up with better cost estimates and options for new GPS satellites, according to a September 9 report from the U.S. Government Accountability Office (GAO). The GAO was responding to an Air Force study on lower-cost space solutions for GPS.
“More information on key cost drivers and cost estimates, and broader input from stakeholders would help guide future investment decisions,” the GAO concluded. Specifically, the key cost drivers include dual-launch capability, navigation satellites (smaller GPS-type satellites yet to be developed), and a nuclear detection capability.”
New Birds by Fall. Galileo satellite-builder OHB AG said it should know by late September whether tests of the first Full Operational Capability (FOC) Galileo satellites are proceeding well enough to permit their delivery later this year. The first FOC satellite began testing at ESA’s European Space Research and Technology Centre in May, and the second arrived August 9.
The OHB satellites either “bear a strong resemblance” or “are identical” to the four in-orbit validation spacecraft now in medium-Earth orbit, depending on the source. However, the on-board power of the OHB spacecraft exceeds that of the validation satellites built by a different manufacturer. According to one source, Galileo managers made the modification in part to enable Galileo’s encrypted Public Regulated Service signal to overcome a signal frequency overlap issue with China’s BeiDou constellation.
