Depending on your age, 30 years represents a varying opinion of time. For some, it may seem like forever; for others, it may be a blink of an eye. In respect to technology, it can represent a complete change in the way we do things.
When we turned the calendar page to January 1990, our world had yet to experience the internet, the Hubble telescope had not been deployed to share its fantastic views, and The Simpsons television series was preparing to become the cartoon juggernaut it remains today.
Yes, lots has changed since 1990, and surveying is no exception.
Most professions look back through their history and see various periods where discoveries and inventions revolutionized how the work was completed.
For surveyors, the past 30 years have contained more advancements than all other years combined, with the greatest achievement being the global navigation satellite system (GNSS). With the United States leading the way with its Global Positioning System and the civilian ability to use this measuring system, modern surveying was forever changed.
Solar and lunar observations replaced
Before the implementation of a satellite navigation system, true global navigation was only computed using solar and lunar readings under specific conditions. GPS provided a new frontier for surveyors to establish positions without having to perform traversing from known points or collecting solar/lunar observations.
As the constellation grew, it became easier to use GPS to gain initialization for accurate and redundant position determination. As processor speeds and data storage capability increased, real-time kinematic (RTK) observations became the norm for surveyors everywhere.
The Russian satellite constellation, GLONASS, began operating fully in the late 1990s, and is now included to create today’s GNSS. More satellites provide more coverage, which in turn means more data collection potential.
Many nations and regions are building their own constellations to augment the current GNSS lineup, and also to safeguard the ability to obtain geographic locations when other systems are not available.
Bathymetric surveys made easy
GNSS capability and integration revolutionized several aspects of surveying, including a new and more reliable way of performing bathymetric surveys over large bodies of water. Computerized depth sounders were programmed to coincide readings with GNSS data collection to provide a more accurate and precise method of hydrographic surveying.
The past decade has continued the reliance on GNSS technology with many more devices and applications — not just for the surveyor, but for the public as well. While surveyors are using GNSS receivers on unmanned vehicles such as UAVs and boats, satellite navigation has infiltrated into many of our everyday routines. Cellphones, fitness trackers and our automobiles use this technology to guide us to our destinations.
Surveyors have used the GNSS revolution to create a digital world for better data collection, asset management and increased efficiency. Much has changed in 30 years for the surveyor and the world around us, so we should not be surprised about what technology will bring us next.
An artist’s rendering of a Galileo satellite in orbit (Image: ESA)
News from the European Space Agency
As European governments plan their phased recoveries from the lockdown states triggered by the COVID-19 pandemic, the positioning delivered through satellite navigation is becoming more important than ever before, said the European Space Agency (ESA). Location is a key requirement when attempting to monitor and map the spread of a disease and satnav is one of the main tools supporting this, the agency added.
Since the outbreak of the coronavirus, many applications have been developed that use satnav-based location data to monitor the global spread of the virus and map outbreaks.
For example, Romanian company RISE developed an app called CovTrack, which monitors people in a user’s vicinity made identifiable via Bluetooth connections to the user’s mobile phone and stores the identification data of these devices.
By pressing a button, users can access the database in which the unique identifiers of the mobile phones are registered (without having access to any personal data of these mobile phone users), to verify whether the persons with whom users came in contact have subsequently been confirmed with COVID-19, ESA said. If users have identified a potential contact, they can refer to the relevant authorities whether that contact requires inclusion among the monitored persons, or even testing for COVID-19.
According to ESA, CovTrack, developed on a pro-bono basis, is a spin-off from the existing AGORA project for festival management, supported through ESA’s Navigation Innovation and Support Programme, focused on future navigation technologies.
ESA, along with the European Global Navigation Satellite System Agency (GSA) and European Commission, put together a repository of these apps. The list, based on apps that are already working and available in app stores, includes practical apps that facilitate the daily lives of citizens. Check out the list here.
Europe’s Galileo, currently embedded in over 1.3 billion smartphones and devices worldwide, is helping to increase satnav accuracy and availability, especially in urban areas, ESA added.
In addition, GSA is developing its own Galileo-enabled application, Galileo for Green Lane, to monitor and ease the circulation of goods between European Union (EU) Member States while identifying potential congestion at Green Lane border crossings, thus ensuring EU citizens can access the needed supplies of critical goods.
Four new satellites of the BeiDou Navigation Satellite System (BDS) have passed tests in orbit and joined the system to provide positioning, navigation and timing services, according to China news service Xinhuanet.
The four satellites include the 47th, 48th, 52nd and 53rd satellites of the BDS family, according to China’s Satellite Navigation System Management Office.
All of them, operating in medium Earth orbit, were developed by the China Academy of Space Technology under the China Aerospace Science and Technology Corporation.
The 47th and 48th BDS satellites were launched on Sept. 23, 2019, and the 52nd and 53rd BDS satellites were launched on Dec. 16, 2019.
Two to the Last. The China Satellite Navigation System Management Office said the last two Beidou-3 satellite launches will take place in March and May, and complete the Beidou system.
China began to construct its navigation system, named after the Chinese term for the Big Dipper constellation, in the 1990s and started serving the Asia-Pacific Region in 2012.
Over the past two years, China has successfully sent 28 BDS-3 satellites and two BDS-2 satellites into orbit.
China plans to launch more BDS satellites in March and May to complete the global network.
The 10-day school will cover all aspects of satellite navigation, up to and including the creation of a satnav-based business. It is open to graduate students, Ph.D.s and postdoctoral researchers, as well as young engineers and academics working within industry or agencies, aged 35 or younger.
The number of participants is limited to 50, on a first-come, first-served basis.
Internationally renowned scientists and specialists will be giving lectures as well as overseeing practical exercises and lab work.
Participants will receive a full-spectrum overview of satellite navigation, starting from the theoretical basis of Global Navigation Satellite Systems, their signals, the processing performed by signal receivers and how the position-navigation-time solution is worked out.
Also discussed will be threats to the satnav systems, such as spoofing or jamming, and countermeasures available against them, along with back-up navigation solutions for a GNSS-denied environment.
Practical exercises will include receiving the various satnav constellations now in orbit — including Europe’s Galileo — to give course members direct, hands-on experience.
In addition, lectures will cover business aspects, including patents and intellectual property rights.
The main emphasis of the course will be the development of a group business project, building on an innovative idea to take in the planning of the product or service, its technical realisation and finally its marketing to customers.
Image: Summer School
The school takes place in cooperation with Stanford University in the United States, the Institut Supérieur de l’Aeronautique et de l’Espace ISAE-SUPAERO in Toulouse, France, Graz University of Technology in Austria, and the University FAF Munich in Germany.
Austria is this year’s host nation, and the summer school is supported by Graz University of Technology and the Austrian Institute of Navigation.
By Peter Steigenberger, Steffen Thoelert, André Hauschild, Oliver Montenbruck and Richard B. Langley
INNOVATION INSIGHTS with Richard Langley
POP QUIZ: What is the most populous metropolitan area in the world? According to Wikipedia, it is Tokyo. In fact, Japan has three cities in the list of the 50 largest cities in the world. Not only are there a lot of people in these cities, they also have many tall and densely packed buildings. And that’s a problem for GPS and the other global navigation satellite systems.
Radio signals travel in straight lines. Well, mostly so. At very low frequencies, radio waves propagate as ground waves and can achieve long-distance propagation in the waveguide formed by the surface of the Earth and the ionosphere. At slightly higher frequencies, such as those used by AM radio, signals still travel as ground waves. However, additionally, the signals propagate upwards as skywaves. During daylight hours, the D layer of the ionosphere absorbs the skywaves, but when the D layer dissipates at night, the higher ionospheric levels can reflect skywaves back to Earth allowing long-distance reception. And communication by shortwave is virtually all by ionosphere-bounce skywaves. Above 30 MHz or so, signals normally travel along line-of-sight raypaths. The atmosphere can slightly bend the raypath, but the signals essentially travel in straight lines. Of course, that’s what makes GPS possible.
GPS works exceedingly well as long as a receiver’s antenna has a line-of-sight “view” of the satellites. Obstacles such as mountains and buildings block the relatively weak GPS signals. In concrete canyons, for example, that may leave a receiver with fewer than four satellites in view, meaning that 3D positioning is impossible. Even if four or more satellites are visible, they may be bunched together in the sky, resulting in high dilution of precision values and potentially large position errors.
In an effort to alleviate the GPS positioning problem in both urban and mountainous areas of Japan, the Japanese government has developed the Quasi-Zenith Satellite System (QZSS). A constellation of three inclined geosynchronous orbit (IGSO) satellites and one geostationary satellite transmits GPS-compatible signals to enhance positioning availability and accuracy. The IGSO satellites have repeating figure-eight ground tracks with the satellites spending most of their one-sidereal-day orbit, centered around apogee, over the Japanese archipelago. The satellites sequentially hover in the sky near the zenith for long periods of time. The satellites also provide both standard and advanced augmentation signals.
The first, or prototype, Block I QZSS satellite was launched in 2010 and, based on the positive test results from this satellite, an additional three satellites were launched in 2017, completing a four-satellite constellation. In this month’s column, we examine the recent developments of this unique and innovative navigation system.
With the launch of two additional spacecraft in August and October 2017, the Japanese Quasi-Zenith Satellite System (QZSS) reached the goal of a four-satellite constellation with the first fully-operational services expected to start in 2018. Aug. 19, 2017, marked the launch of QZS-3, the first geostationary Earth orbit (GEO) QZSS satellite, while the third spacecraft in inclined geosynchronous orbit (IGSO), QZS-4, was subsequently launched on Oct. 10, 2017. An artist’s view of the constellation is shown in FIGURE 1.
FIGURE 1. An artist’s view of the QZSS satellites. The upper-most satellite is the geostationary QZS-3 spacecraft with the additional S-band dish antenna whereas the other satellites pictured are the inclined geosynchronous satellites. (Image: Mitsubishi Electric)
Table 1 lists the four satellites of the current QZSS constellation. Whereas the first generation Block I satellite QZS-1 was launched in 2010, the three Block II satellites joined the constellation in 2017.
Table 1. QZSS constellation as of December 2017. SVN: space vehicle number, PRN: pseudorandom noise (code number), IGSO: inclined geosynchronous orbit, GEO: geostationary Earth orbit.
The most obvious visual difference between the QZSS Block I and II satellites is the different number of subpanels for the solar arrays: three for the Block I satellite and two for the Block II satellites with spanned widths of 25.3 meters and 19.0 meters, respectively. The reduced size of the Block II array has been achieved through the use of new, high-efficiency solar cells. The GEO satellite in addition carries S- and Ku-band antennas with diameters of 3.2 meters and 1.0 meter, respectively. While the IGSO satellites are equipped with a helix antenna array for transmission of the main L-band navigation signals, the GEO satellite uses a patch antenna array similar to that of the Galileo satellites.
The ground tracks of the four QZSS satellites are plotted in FIGURE 2. The ground tracks of all of the IGSO satellites have the characteristic figure-eight shape due to the large orbit eccentricity of 0.075 and results in a longer visibility period for users in the northern hemisphere. The ground tracks do not precisely match, however. QZS-1 and QZS-4 have similar orbit inclinations (with respect to the equator) of 40.9° and 40.5°. QZS-2, on the other hand, has a larger inclination of 44.5°, which leads to a wider extension of the ground track in the north-south direction.
FIGURE 2. Ground tracks of the four-satellite QZSS constellation as of Dec. 4, 2017. The blue square indicates the sub-satellite point of the geostationary QZS-3 satellite. (Image: Authors)
Also, the central longitude of the ground tracks, which marks the center of the figure-eight shape, varies between 130° and 140° E. These differences are still within the tolerances defined in the QZSS Interface Specification, version 1.8 of Oct. 3, 2016, which specifies the inclination to be 43° ± 4° and the central longitude of the ground track to be 135° ± 5° E. The GEO satellite QZS-3 is located at 127° E and has been controlled to stay within a 0.1° inclination window since achieving its initial orbit.
All QZSS satellites transmit navigation signals in the L1, L2 and L5 bands compatible with GPS, namely L1 C/A, L1C, L2C and L5 (the Positioning, Navigation and Timing or PNT service). QZSS-specific signals are transmitted in the L1, L5 and L6 bands: the Sub-meter Level Augmentation Service or SLAS (formerly, Submeter-class Augmentation with Integrity Function or SAIF) signals for all satellites on L1 and, in addition, on L5 for Block II satellites (see TABLE 2).
Table 2. QZSS signals. The L2C and CLAS signals use interleaved bit streams for concurrent transmission of two independent ranging sequences. The L1S signal consists of SLAS, a message service, and L1Sb, an SBAS signal. (Based on Table 11.2 in the Springer Handbook of Global Navigation Satellite Systems).
Starting in 2020, the GEO satellite will also provide a satellite-based augmentation system (SBAS) signal called L1Sb with range corrections and integrity information for aviation applications in particular. The SLAS and SBAS signals are transmitted via dedicated antennas but they are phase coherent with the GPS-compatible navigation signals transmitted via the main L-band antenna. The L6 signal provides the Centimeter Level Augmentation Service or CLAS (formerly, the L-band Experiment or LEX) on all QZSS satellites, but employs a different signal structure for Block I (L61) and Block II (L62). An overview of the various L-band signals and corresponding PRN assignments is given in TABLE 3. QZS-3 also provides the QZSS Safety Confirmation Service (Q-ANPI) to support rescue operations with S-band communication in case of a disaster. The total transmit power is 500 watts for the Block II IGSO satellites and 550 watts for the GEO satellite.
Table 3. PRN code assignment of QZSS satellites according to the interface specifications (see Further Reading). RINEX: PRN code in RINEX observation files; NAV: PRN code for L1 C/A, L1C, L2C and L5 navigation signals; NSTD: non-standard codes of IGSO/GEO satellites.
QZS-3/4 SIGNAL TRANSMISSION
Tracking of the QZS-3 L1 C/A and L5 signals by receivers in the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt or DLR) and International GNSS Service networks started on Sept. 10, 2017, at 09:04 UTC followed by the L1C and L2C signals at 09:27 UTC. L5 tracking started with a very low carrier-to-noise-density ratio (C/N0) of 10 – 20 dB-Hz that increased to 50 – 55 dB-Hz shortly after the activation of the L1C and L2C signals. QZS-3 broadcast ephemerides were first transmitted on Oct. 4, 2017, at 16:00 UTC. However, tracking of the L1, L2 and L5 navigation signals with common geodetic receivers is currently limited to receivers with experimental firmware versions developed by three different manufacturers.
Signal transmissions from QZS-4 started on Nov. 1, 2017. The first L1 C/A signals of PRN J03 were received at 02:50 UTC. At the same time, L5 signal transmission started but this signal was only tracked by a very limited number of receivers due to its low signal strength resulting in a C/N0 of only about 15 dB-Hz. At 03:14 UTC, an increase of the C/N0 by about 40 dB occurred and many additional receivers started tracking the L5 signal. At the same time, the L1C and L2C signals were also activated followed by the L1 SLAS signal at 03:20 UTC.
It is interesting to note that QZS-4 also transmitted the non-standard code J06 on different frequencies during its first weeks of operation. This code cannot be used for positioning and is used for test purposes or in case of system errors. Until Nov. 27, 2017, QZS-4 regularly switched between transmission of standard and non-standard codes. An example of such a switch for the station UNX200AUS located in Sydney, Australia, is shown in FIGURE 3. During this test period, several outages of individual or all navigation signals also occurred. Since Nov. 24, 2017, 5:00 UTC, broadcast ephemerides of QZS-4 have been available and transmission of the L5 SLAS signal started at 09:31 UTC.
FIGURE 3. QZS-4 signals tracked by DLR’s JAVAD Delta-3TH receiver in Sydney, Australia. The top plot shows the standard code PRN J03 and the bottom plot the non-standard code J06. The measured C/N0 is shown for L1 C/A (black), L1C (blue), L2C (red) and L5 (green). (Image: Authors)
FIGURE 4 shows the L-band normalized power spectra of QZS-2 and QZS-4. The spectra were obtained from in-phase (I) and quadrature (Q) data recorded with DLR’s 30-meter high-gain antenna in Weilheim, Germany. Almost identical characteristics can be seen for the signals of both satellites in the L1, L2 and L6 bands. However, in the L5 band, QZS-4 shows a slightly lower power than that of QZS-2 due to the lack of the L5 SLAS transmission during the data recording. Unfortunately, QZS-3 is not visible from Weilheim due to a longitude difference of more than 115°.
FIGURE 4. Normalized power spectra of QZS-2 and QZS-4 measured with DLR’s 30-meter high-gain antenna on July 18, 2017, and Nov. 7, 2017, respectively. (Image: Authors)
ATTITUDE
Usually, QZS-2 and QZS-4 follow a nominal yaw steering attitude with the spacecraft z-axis pointing towards the Earth and the y-axis (solar panel axis) oriented perpendicular to the plane defined by the locations of the satellite, the Sun, and the Earth. The maximum yaw rate of these satellites is limited to 0.055° per second and can be exceeded by the nominal yaw rate when the angle of the Sun with respect to the orbital plane (the beta angle, β) is between -5° and +5°. During orbit control maneuvers, the QZSS Block II IGSO satellites are operated in orbit normal mode with the z-axis pointing to the Earth and the y-axis perpendicular to the orbital plane. The geostationary QZS-3 satellite is continuously operated in orbit normal model while QZS-1 enters orbit normal mode for |β| < 20°.
Detailed information about the different attitude rules as well as spacecraft reference frame, mass, center of mass, phase center offsets and variations of the navigation antenna, laser retroreflector offsets, satellite group delays as well as the total transmit power of all four satellites is provided by the Cabinet Office, Government of Japan, in the QZSS satellite information documents.
Since all QZSS satellites are equipped with a separate L1 SLAS transmit antenna, which is mounted with an offset to the main L-band antenna, each satellite’s attitude can be directly estimated from single-difference carrier-phase observations between the two spacecraft antennas.
FIGURE 5 illustrates the attitude of QZS-4 estimated from L1 C/A and L1 SLAS observations from 10 tracking stations as well as the nominal yaw steering attitude. QZS-4 had a beta angle of about 11° on Dec. 9, 2017, confirming that this satellite does not enter orbit normal mode for |β| < 20° as does QZS-1. Differences between nominal yaw steering attitude and estimated attitude are usually within ±1.5° reflecting estimation errors as well as differences between nominal and true attitude.
FIGURE 5. Nominal yaw steering attitude (blue) and estimated attitude (red) of QZS-4 for Dec. 9, 2017 (β ≈ 11°). (Image: Authors)
CLOCK PERFORMANCE
The clock stability represented by the modified Allan deviation is given in the upper panel of FIGURE 6 for the QZSS IGSO satellites. The QZSS Block II IGSO satellites show an almost identical stability for integration periods up to 100 seconds. For longer periods, the QZS-2 clock seems to perform slightly better.
However, this effect is probably related to the number of stations contributing to the clock solutions of the individual satellites which differs by a factor of more than two. For comparison purposes, the Allan deviation of two Galileo rubidium clocks (GAL-101 and GAL-204) and a Galileo passive hydrogen maser (PHM, GAL-207) are plotted in the bottom panel of Figure 6.
Whereas the performance of the QZSS and Galileo rubidium clocks is very similar, the Galileo PHM is more stable by a factor of two to five over all integration periods.
FIGURE 6. Modified Allan deviations of the QZSS IGSO rubidium clocks, Galileo rubidium clocks (GAL-101 and GAL-204) and a Galileo passive hydrogen maser (GAL-207). (Image: Authors)
CONCLUSIONS
With the launch of the third IGSO spacecraft and the first GEO spacecraft, the QZSS constellation has reached a four-satellite configuration, which is required for the provision of operational augmentation services. QZS-3 and QZS-4 were declared useable for PNT, SLAS, and CLAS trial services on Dec. 18, 2017, and Jan. 12, 2018, respectively. Inclusion in the operational QZSS constellation is expected for 2018 and this will provide continuous visibility of three satellites in the service area. An expansion to a constellation of seven satellites is planned for 2023 including a Public Regulated Service for authorized users.
MANUFACTURERS
Data used in this article was collected using Javad GNSS Delta-G3TH, Trimble NetR9 and Septentrio PolaRx4 and PolaRx5 receivers.
Authors Peter Steigenberger, Steffen Thoelert, André Hauschild and Oliver Montenbruck are from the German Aerospace Center (DLR).
Richard B. Langley is from the University of New Brunswick and authors the monthly “Innovation” column for GPS World magazine.
FURTHER READING
• Quasi-Zenith Satellite System
“Quasi-Zenith Satellite System” part of “Regional Systems” by S. Kogure, A.S. Ganeshan and O. Montenbruck, Chapter 11 in Springer Handbook of Global Navigation Satellite Systems, edited by P.J.G. Teunissen and O. Montenbruck, published by Springer International Publishing AG, Cham, Switzerland, 2017.
“QZS-2 Signal Analysis, QZS-3 Launched” by S. Thoelert, A. Hauschild, P. Steigenberger, O. Montenbruck and R.B. Langley in GPS World, Vol. 28, No. 9, September 2017, pp. 10–14.
The Institute of Navigation’s (ION) Satellite Division presented Professor Terry Moore with its Johannes Kepler Award for his outstanding contributions to the development of satellite navigation through a sustained and distinguished professional career devoted to research and teaching.
Moore received the award Sept. 29 at the ION GNSS+ Conference in Portland, Ore. Moore is a member of the GPS World Editorial Advisory Board.
Terry Moore has more than 30 years of research experience in surveying, positioning and navigation technologies, and is a consultant and advisor to European and U.K. government organizations and industry.
He has taken a leading role in national and European initiatives aimed at integrating academic research and teaching activities in GNSS and interacting closely with industry.
Moore is credited with extensive work on the introduction and implementation of WGS 84 as the standard reference systems for air and marine navigation, as well as the development of standard software tools for coordinate transformations and map projections used extensively through the aviation industry.
Additionally, he is known for the development of GRINGO software that pioneered the use of raw GPS code and carrier phase data from low cost Garmin receivers. His work has also includes the pioneering of novel methods and algorithms for GPS orbit relaxation; which led to reduced dynamic GPS-based orbit determination for LEO spacecraft, with a real-time implementation.
Moore is the Director of the Nottingham Geospatial Institute (NGI) at the University of Nottingham where he has responsibility for all of NGI’s research and teaching. He is also the founding Director of GRACE, the GNSS Research and Applications Centre of Excellence, which was jointly funded by the University of Nottingham and East Midlands Development Agency, and targets knowledge transfer between the NGI and business. Additionally, he leads the university-wide Aerospace and Transport Technology Research Priority Area.
Moore has supervised numerous research projects funded by industry, research councils, the European Space Agency and the European Commission, and has supervised more than 30 Ph.D. students.
Moore is involved in the volunteer activities of numerous international professional and scientific bodies. He is currently a Royal Institute of Navigation (RIN) Vice-President (now also President Elect) and a member of their Technical Committee, while simultaneously serving on the ION Council as a Technical Representative and as a co-chair of the ION’s Satellite Division’s Technical Peer Review Committee.
He has served on the ION’s Satellite Division Executive Committee on numerous occasions and is a past ION GNSS+ program and general chair.
Moore is a Fellow of both the Institute of Navigation and the Royal Institute of Navigation (RIN). He is also a Fellow of the Chartered Institution of Civil Engineering Surveyors, a Fellow of the Royal Astronomical Society and an Associate Fellow of the Remote Sensing and Photogrammetry Society. In 1999 and 2008 he was awarded the RIN Richey Medal (best paper in the RIN Journal of Navigation), in 2013 was awarded the RIN Harold Spencer-Jones Gold Medal (outstanding contributions to navigation), and in 2016 the RIN J.E.D. Williams Medal (contributions to the RIN).
He holds a BSc degree in Civil Engineering and Ph.D. degree in Space Geodesy, both from the University of Nottingham, where he was promoted to the U.K.’s first Chair of Satellite Navigation in 2001.
The Johannes Kepler Award recognizes and honors an individual for sustained and significant contributions to the development of satellite navigation. It is the highest honor bestowed by the ION’s Satellite Division.
Ten years ago saw the launch of Europe’s very first navigation satellite. A decade of hard work later, more than a third of the Galileo constellation has followed it into orbit and a ground network sharpening the satnav system’s accuracy encompasses the globe.
Galileo’s GIOVE-A retired in June 2012. (Photo: ESA)
GIOVE-A, short for Galileo In-Orbit Validation Element-A, was launched by Soyuz from Baikonur cosmodrome in Kazakhstan on Dec. 28, 2005.
“Much work had already taken place on the ground, but GIOVE-A marked the first time that Galileo hardware went into orbit,” recalls Didier Faivre, heading ESA’s navigation directorate.
“It had a crucial role: to claim operating frequencies that had been set aside for Galileo by the International Telecommunications Union, to demonstrate essential technologies such as Galileo’s rubidium atomic clock, and to gather data on the radiation-rich environment of medium-altitude orbit, which was a relatively unknown region for Europe.
Didier Faivre (Photo: ESA)
“So GIOVE-A opened the way to all that followed — the follow-up GIOVE-B in 2008, and then the launches of the Galileo satellites proper — a total of six double-satellite launches from 2011 to earlier this month, with 12 satellites placed in orbit so far, on the way to the full 30-satellite constellation.
“Our three launches this year doubled the number of satellites in orbit, and the pace of progress is set to increase further in 2016, when we will see Ariane 5 called on to launch Galileo for the first time, doubling the number of satellites released on each flight.”
Progress in space has been mirrored on Earth, with the establishment of Galileo’s ground segment: two control centers in Fucino, Italy, and Oberpfaffenhofen, Germany, sit at the heart of a worldwide network of ground stations.
The Soyuz launcher carrying GIOVE-A climbs into the sky above Kazakhstan on Dec. 28, 2005. (Photo: ESA)
This ground segment, as one of the most complex infrastructures ever overseen by ESA, has the task of keeping all the satellites healthy and their navigation signals synched — the timing system accurate to a few billionths of a second that provides the submetre precision.
Sensor stations to monitor Galileo signals and return data to the control centers are required all across the vast footprint of the system. Their locations range from the Arctic to Antarctic to lonely mid-ocean islands, all connected back to Europe via satellite.
Initial Galileo services are set to be available during next year. New generations of commercial satnav receivers are already Galileo-ready, having received extensive technical checks from ESA’s Navigation Laboratory.
GIOVE-A in a clean room at ESA’s ESTEC technical centre in the Netherlands, having instrumentation sensors installed in advance of testing in 2005. (Photo: ESA)
And national governments are already preparing to make use of Galileo’s Public Regulated Service — PRS, the most secure and precise class of service, restricted to authorized users. Belgium, France, Italy and the UK have all performed their own PRS acquisitions and positioning testing.
As for GIOVE-A, the satellite that started it all, its ESA mission concluded in 2012, once the first four Galileo satellites followed it to orbit. Remarkably, it is still operational, controlled by builder Surrey Satellite Technology Ltd in the UK.
In the past it has carried out tests of high-altitude satnav detection. Its radiation monitor continues monitoring the medium-altitude orbit environment, helping to forecast the future long-term performance of its Galileo descendants.
Crowds gather at the GPS World booth at ION GNSS+ 2014.
ION GNSS+ 2015 is the 28th International Technical Meeting of the Institute of Navigation’s Satellite Division and the world’s largest technical meeting and showcase of GNSS technology, products and services and other sensors in today’s marketplace. The conference will be held Sept. 14-18 (tutorials Sept. 14-15) at the Tampa Convention Center in Tampa, Fla.
James L. Green, director of Planetary Science for NASA, will take the audience on a journey navigating through the solar system during his keynote address. He will show new worlds and new discoveries through the eyes of NASA’s planetary spacecraft.
This year’s conference will feature panels of industry experts, policy updates, the world’s largest GNSS commercial exhibit and more than 300 technical presentations presented through both Peer-Reviewed Tracks (Multisensor Navigation and Applications; Algorithms and Methods; and Advanced GNSS Technologies) and Systems and Application Tracks (Mass-Market Applications; High Performance & Safety-Critical Applications; and System Updates, Plans and Policies).
GPS World staff will be moderating the Lightning Talks section of the plenary session, as well as hosting a booth in the Exhibit Hall.
Tap into our up-to-the-minute show coverage here at gpsworld.com and via Twitter (@GPSWorld).
Alan Cameron, GPS World Editor and Publisher, provides the following video introduction to the conference.
Avanti Communications has been appointed by the UK Space Agency to deliver a crucial air navigation project in Africa, SBAS-AFRICA. The satellite operator has been awarded the contract under the agency’s International Partnership Space Programme (IPSP), which exists to open up opportunities for the UK space sector to share expertise in real-world satellite technology and services overseas.
Africa has just 3 percent of global air traffic, and yet air accidents in Africa account for roughly 20 percent of the worldwide total. By demonstrating potential improvements in flight safety via SBAS technologies, the project can provide socio-economic benefits to the continent, according to a news release from Avanti.
Based on prior cost-benefit modeling which identified a €1.7 billion potential economic benefit to the African aviation sector from the deployment of SBAS services, SBAS-AFRICA will help accelerate the adoption of GNSS-based flight operations, positively influence the evolution of aviation safety in Africa and encourage development in the wider African economy.
SBAS-AFRICA will deliver a satellite-based augmentation system for GNSS-based operations in the aviation sector, serving significant parts of Africa in partnership with a number of local stakeholders. The project will use a unique asset, Avanti’s ARTEMIS L1 Navigation transponder, to provide a navigation data broadcast service.
“SBAS-AFRICA brings an innovative and pragmatic approach to deploying SBAS services in Africa,” said Matthew O’Connor, Chief Operating Officer at Avanti Communications. “It establishes crucial collaboration between the UK and a number of African countries, including South Africa and Ghana. Participating countries will benefit hugely from expertise gained, placing them at the forefront of navigation services across the continent and, crucially, helping to improve aviation safety for a major generator of economic benefit in Africa.”
He continued, “The Artemis satellite will play an integral role in this project. We expect that such a showcase for its performance, accuracy and quality will provide further evidence of what can be achieved with this technology and lead to significant commercial opportunities.”
“The UK Space Agency is delighted to play a role in fostering new international partnerships that not only enable innovative UK space companies like Avanti to provide more high-tech exports that can boost our space sector but also allow the UK to widely share the considerable social and economic benefits that space technology and infrastructure can provide,” said David Parker, chief executive of the UK Space Agency.
The United Nations is spotlighting the benefits of satellite navigation and its contribution to the betterment of humankind as part of the observance of World Space Week — an annual global celebration of the contributions of space science and technology to humanity.
The theme of this year’s World Space Week is Space: Guiding Your Way. It highlights the benefits of satellite navigation to society, which Simonetta Di Pippo, director of the UN Office for Outer Space Affairs (UNOOSA), said are of “great importance” to her office. UNOOSA also functions as the Executive Secretariat to the International Committee on Global Navigation Satellite Systems (ICG), which promotes voluntary cooperation on civil satellite-based positioning navigation, timing and value-added services.
Proclaimed by the UN General Assembly in 1999, World Space Week, observed each year during the week of October 4-10, aims to provide unique leverage in space outreach and education; educate people around the world about the benefits that they receive from space; encourage greater use of space for sustainable economic development; demonstrate public support for space programs; excite young people about science, technology, engineering, and math; and foster international cooperation in space outreach and education.
The dates recall the launch on October 4, 1957, of the first artificial satellite, Sputnik I, and the entry into force, on October 10, 1967, of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space including the Moon and Other Celestial Bodies.
Ideas for educators and youth groups to focus on satellite navigation include geocaching, building model satellites, and using Google Earth. “Imagine a world without navigation satellites to guide planes, ships and cars and not to forget: us with our location-based mobile phone applications!” the guide states. “And navigation satellites not just accurately pinpoint our position on the planet, it also provides time signals to keep clocks in sync, which is critically important for global trading and many other time critical sectors. In times of disaster navigation satellites help rescuers quickly find spots where people need help. Using Geographic Information Systems (GIS) we can compare maps before and after things changed. And GNSS satellites are important to help you planning your trips and tell you where it will rain and where it will shine!”
