China has launched its first geostationary satellite for the BeiDou constellation, according to press reports.
The successful launch of satellite G1Q took place at 15:57 UTC on Nov. 1 from the LC2 Launch Complex of the Xichang Satellite Launch Center, Sichuan province, using a Long March-3B/G2 (Chang Zheng-3B/G2) launch vehicle.
Beidou-3G satellites are the geostationary Earth orbit (GEO) component of the third phase of the Chinese Beidou satellite navigation system. The GEO satellites will be in high orbit, about 36,000 kilometers above the Earth, following the Earth’s rotation to view the same point on Earth continuously.
In addition to navigation services, the satellite will serve as a satellite-based augmentation system (SBAS) and provide short message services (Research Data Shared Service, RDSS).
The G1Q satellite is the 17th BeiDou-3 satellite and the 41st overall BeiDou satellite. Another pair of BeiDou-3 medium Earth orbit (MEO) satellites, M17 and M18, will be launched in mid-November.
The recent BeiDou launches will expand the system to global navigation coverage.
The G1Q satellite is based on the DFH-3B bus that features a phased array antenna for navigation signals and a laser retroreflector, and also is equipped with an apogee propulsion system for final orbit insertion. The satellite has a launch mass of about 4,600 kg.
Duro Inertial is a ruggedized version of Swift Navigation’s Piksi Multi dual-frequency real-time kinematic (RTK) GNSS receiver combined with CRL’s SmoothPose sensor fusion algorithm, which fuses GNSS and inertial measurements into a combined solution.
The blending of GNSS and inertial measurements provides a dead-reckoning capability that allows Duro Inertial to provide a highly accurate, continuous position solution during brief GNSS outages and to deliver a robust precision navigation solution in harsh GNSS environments.
Duro Inertial is an evolution of Swift and CRL’s first joint product, Duro. Building on the on-board MEMS inertial measurement unit (IMU) that exists in Duro today, Duro Inertial harnesses CRL’s loosely coupled (LC) sensor fusion algorithm, SmoothPose, to blend GNSS and inertial inputs, providing a smoother, more available and more robust position, velocity and time (PVT) solution, the companies said.
Duro Inertial seamlessly blends CRL’s SmoothPose GNSS+INS algorithms with Swift Navigation’s Starling Positioning Engine to deliver a highly-accurate LC positioning solution even in GNSS / RTK denied environments.
The inertial aiding feature can operate with RTK, autonomous GNSS and satellite-based augmentation system (SBAS) position solutions from Starling. Duro Inertial also inherits the full set of features from Duro and Piksi Multi including the light-weight SBP communication protocol, interoperability with legacy protocols such as NMEA output and RTCMv3 input, compatibility with RTK corrections services such as Skylark, Swift’s Cloud Correction Service and many third-party corrections services, and quad-constellation dual-frequency RTK navigation.
The combination of Duro Inertial’s positioning accuracy and its ruggedized enclosure that protects against weather, moisture, vibration, dust and water immersion makes it suitable for construction, mining, logistics, positive train control, robotics and agriculture applications.
“We are excited to introduce our second collaboration with Carnegie Robotics and build on the success of the Duro ruggedized receiver launched last year,” said Timothy Harris, co-founder and CEO of Swift Navigation. “The combination of Carnegie Robotics’ advanced inertial technology and robotics expertise with Swift’s positioning solution will enable an even broader customer segment to benefit from highly-accurate positioning.”
“Duro Inertial is the culmination of our partnership with Swift over the past two years,” added John Bares, CEO of Carnegie Robotics. “Working together we are able to deliver a consistent and highly-accurate positioning solution to benefit a variety of robotics and industrial applications.”
Duro Inertial is scheduled to be available at for purchase in the fourth quarter and is now available for select customer testing.
A FreeFlight Systems SBAS/GNSS receiver has been selected to provide ADS-B position source information as a part of an upcoming ADS-B modification and compliance program for the United States Air Force HH-60G helicopter fleet.
Strategic Enterprise Solutions Corp. (SESC) of Warner Robins, Georgia, was awarded the modification program, which includes installation of the 1203C SBAS/GNSS receiver and the AN/APX-119 Mode S Extended Squitter transponder with Mode 5 capability to provide a complete ADS-B Out solution for more than 100 helicopters.
An HH-60 Pave Hawk helicopter lands in Afghanistan; a UH-60 Blackhawk is in the background. (Photo: U.S. Air Force photo/Senior Airman Brian Ferguson)
The FreeFlight Systems 1203C SBAS/GNSS receiver is a certified, high-integrity position source in a compact, lightweight package that was designed to be modular and able to be integrated with various other avionics.
The 1203C pairs seamlessly with certified Mode S Extended Squitter transponders for a fully rule-compliant ADS-B Out system, FreeFlight said.
More than a war hawk. The primary mission of the HH-60G Pave Hawk helicopter is to conduct day or night personnel recovery operations into hostile environments to recover isolated personnel during war.
The HH-60G is also tasked to perform military operations other than war, including civil search and rescue, medical evacuation, disaster response, humanitarian assistance, security cooperation/aviation advisory, NASA space flight support, and rescue command and control.
The 1203C in service. With several hundred 1203Cs in service across airline transport, military, business aviation and rotorcraft platforms, these receivers are known for their high performance, ease of installation, operational reliability and longevity, FreeFlight said.
The 1203C SBAS/GNSS receiver and antenna (Photo: FreeFlight Systems)
The 1203C can also serve as the approved position source for select manufacturers of TAWS/FMS, RNP and other NextGen applications, and allows customers to take advantage of the operational and safety benefits provided by the NextGen airspace transformation without the need for extensive and costly avionics upgrades.
With the ADS-B mandate now only 17 months away, aircraft operators need to prioritize ADS-B installations.
Significant portions of today’s airline, business, and military aircraft fleet will remain in service long after 2020, and in many cases an STC’d retrofit solution comprising of a transponder upgrade and the addition of a dedicated SBAS/GNSS receiver like the 1203C is the simplest and most cost-effective way to achieve mandate compliance, FreeFlight said.
The Australian government is investing in GPS technology that will create jobs and support Australian industry.
Minister for Resources and Northern Australia, Senator Matt Canavan, said the government is investing more than $260 million to develop the satellite technology.
“We rely on satellite and GPS technology for just about every aspect of our lives — from Google Maps on our individual phones, through to air traffic control at the busiest airports,” Canavan said. “More precise technology will make Australian businesses more productive, safer and more efficient.
Specifically, Canavan said, “More accurate GPS will improve productivity by allowing new technology to be created and used across the economy. Growing Australia’s digital economy will also benefit developed sectors such as mining, transport, construction, aviation and agriculture. “This investment will improve competitiveness and secure jobs across the Australian economy.”
SBAS Testbed. Under the package, $160.9 million will deliver a Satellite-Based Augmentation System (SBAS) to improve the reliability and the accuracy of positioning data from five meters to 10 centimeters across Australia and its maritime zone.
The $160.9 million includes funding over four years from 2018-19 and $39.2 million in ongoing funding from 2022-23. It will realize the SBAS testbed, which is currently running across Australia-New Zealand.
CRCSI is an international research and development centre set up in 2003 under the Australian Government Business Cooperative Research Centres Programme. The CRCSI is managing the industry-based demonstrator projects of the SBAS testbed and the economic benefits study. The infrastructure management is being led by Geoscience Australia in partnership with Land Information New Zealand and the global technology companies GMV, Inmarsat and Lockheed Martin.
“We have been coordinating multiple trials of first and second generation SBAS and Precise Point Positioning correction signals since mid-2017,” said Graeme Kernich, CRCSI CEO. “Our industry partners are crying out for this technology because a more precise positioning capability brings far-reaching and lasting impacts.
“Data analysis results and the economic benefits reported from the testbed are very promising and will translate across agriculture, aviation, consumer, construction, maritime, mining, rail, road, spatial and utilities.
“This is a formidable technology story and a practical demonstration of downstream space applications. We are looking forward to continuing the testbed over the coming nine months and assessing the economic and social benefits the operational system will bring to Australia, and possibly New Zealand,” Kernich said.
“The CRCSI has a strong track record of bringing the best people together from the private sector, government and academia to solve the most complex spatial problems; the SBAS testbed is one of the finest examples of this,” Kernich said.
“More accurate and reliable satellite positioning technology will improve the safety and efficiency of many sectors across Australia and New Zealand,” he said. “There are 28 projects across 10 sectors, with over 150 collaborating organizations currently involved in the testbed, making the footprint of this world-first trial truly trans-Tasman.”
National Positioning Infrastructure. A $64 million investment in the National Positioning Infrastructure Capability (NPIC) will complement SBAS to improve GPS to an accuracy as precise as 3 centimeters in areas of Australia with access to mobile coverage.
The national positioning infrastructure project will establish additional ground stations and augment GNSS signals to deliver high accuracy positioning. This will ensure nationally consistent and accurate positioning of 3 centimeters can be provided across Australia in areas with mobile coverage. The project will achieve this by:
building new GNSS ground stations and integrating existing stations to enable multiple GNSS signals to be received for precise positioning across Australia.
establishing a GNSS data analytics capability to verify and correct the positioning signals for the user. This will ensure Australian industry has access to world-leading software tools for positioning.
engaging existing and new industries and service providers to raise awareness of the opportunities positioning opens up for businesses through increased productivity, safety and innovation.
“Our investment in this world-standard technology will have direct benefits including virtual fencing for farms and better management of cattle and livestock over vast distances,” Canavan said.
“It also has applications for regional aviation such as improved access to regional areas by enabling planes to land on smaller airstrips and navigate difficult terrain such as canyons.
“The increased reliability provided by better GPS will improve safety for aircraft flying into regional and remote aerodromes, such as the Royal Flying Doctor Service fleet. It will reduce the impact of weather on flight cancellations and diversions, and improve the safety of landings.
“The resource sector will also benefit through better control of mine infrastructure, safety and more precise data for environmental rehabilitation.
“This is a practical investment to improve the lives of Australians and make businesses more productive. This technology provides instant, reliable and accurate positioning information, anytime and anywhere around Australia.”
Digital Earth Australia. A further $36.9 million is for Digital Earth Australia, a technology that will give Australian businesses greater access to reliable, standardized satellite data that identifies physical changes to the Australian environment.
“The practical benefits of this investment will extend across our economy. This data will help researchers, governments and business better understand environmental changes, such as coastal erosion, crop growth and water quality,” Canavan said. “For example, information drawn from satellites is vital to help graziers increase the capacity of paddocks and make their farms more viable and sustainable.
“Our investment in satellite imagery will ensure a range of Australian industries have access to data that can help them tailor their investments, create jobs in target regions and increase their competitiveness.”
The Federal Aviation Administration’s Geosynchronous Earth Orbiting 5 Wide Area Augmentation System (WAAS) navigation payload, developed by Raytheon’s Intelligence, Information and Services business, is now operational and fully integrated into the WAAS network.
The GEO 5 payload joins two others already on orbit in correcting GPS satellite signal ionospheric disturbances, timing issues and minor orbit adjustments, giving users increased coverage, improved accuracy and better reliability, Raytheon said.
“GPS alone can’t meet the FAA’s stringent requirements for accuracy, integrity and availability,” said Matt Gilligan, vice president of Raytheon’s Navigation, Weather and Services mission area. “The WAAS network corrects even the slightest errors, and that provides peace of mind when it comes to safety of flight.”
In operation since 2003, WAAS increases GPS satellite signal accuracy from 10 meters to 1 meter, ensuring GPS signals meet rigorous air navigation performance and safety requirements for all classes of aircraft in all phases of flight, Raytheon added.
WAAS provides precision navigation service to users across the United States from Maine to Alaska, as well as portions of Canada and Mexico.
For aviation users, WAAS offers pilots more direct flight paths, precision airport approaches and access to remote landing sites without depending on local ground-based landing systems.
Raytheon is the system integrator on the GEO 5 system, which includes a WAAS navigation payload on Eutelsat’s GEO satellite, two ComSAT ground sites and SED Systems specialized equipment.
The European GNSS Agency (GSA) has issued a request for information (RFI) in preparation for the procurement of EGNOS geostationary navigation payload services.
The EGNOS space segment is provided by commercial satellite operators on the basis of service contracts. The GEO-1, GEO-2 and GEO-3 service contracts now cover the EGNOS space segment needs, and the GEO-1 and GEO-2 services will be the first of these to end, GSA reported. The GEO-1 and GEO-2 services will be replaced by new contracts, GEO-4 and GEO-5.
GSA is planning how it will replace the services delivered by the GEO-1 and GEO-2 satellites, and it’s issuing the RFI to collect information about opportunities to embark navigation payloads on board GEO satellites launched in a suitable time frame.
According to GSA, the results of the RFI will also be used to determine the best approach for the procurement of the payload services, which may be either procured at the same time or separately. It will help GSA define the tender specifications and decide on the most appropriate time to launch invitations to tender.
In addition, GSA aims to obtain information from owners of geostationary satellites that will be available for operational service from 2021 to 2027 and able to embark a navigation payload. The agency is specifically seeking information on future satellite plans and the possibility to embark SBAS payloads in due time to ensure an operational start date from 2021 to 2027.
The RFI will also request information service availability and long-term payload reliability; the process for EGNOS payload procurement, in-orbit testing and commissioning; information on the locations of the potential hosting sites for the EGNOS radio frequency uplink stations; and, finally, information on contractual arrangements, the payment scheme, and cost estimates, GSA added.
Answers to the RFI should be sent electronically to [email protected] by Aug. 31.
China has already launched eight BeiDou-3 satellites for its domestic BeiDou Navigation Satellite System. The satellites will provide initial services for countries and regions along the Belt and Road by the end of the year, said Wang Li, chairman of the China Satellite Navigation System Committee.
Addressing the Ninth China Satellite Navigation Conference in Harbin, capital of northeast China’s Heilongjiang Province, Wang said the BeiDou system is moving to become a global service provider after offering stable and reliable time and space information for clients in the Asia-Pacific region.
China launched the first two BeiDou-3 satellites into space via a single carrier rocket in November 2017, as its self-developed BeiDou system officially began to expand into a global network.
Compared to earlier generation satellites, the BeiDou-3 is able to send signals that are more compatible with other satellite navigation systems and provide satellite-based augmentation, as well as search-and-rescue services in accordance with international standards. Its positioning accuracy has reached 2.5 to 5 meters.
Swift Navigation has issued a new firmware upgrade to its flagship product Piksi Multi GNSS module.
This marks the fifth major point release to Piksi Multi and is available free of charge to Swift customers. The most recent provided GLONASS support, among other features.
The firmware release also enhances Duro, the ruggedized version of the Piksi Multi receiver housed in a military-grade, weatherproof enclosure designed for long-term outdoor deployments.
Duro – Piksi enclosure.
Firmware Release 1.5 for Piksi Multi and Duro supports four regional Satellite Based Augmentation Systems (SBAS) — the United States-based Wide Area Augmentation Systems (WAAS), the pan-European Union-based European Geostationary Navigation Overlay Navigation System (EGNOS), the Japanese Multifunctional Transport Satellites (MTSAT) Satellite Augmentation System (MSAS) providing coverage for Japan and Australia and the GPS-Aided GEO Augmented Navigation (GAGAN) regional system operated by the Indian government.
These four regional satellite systems are used to improve the overall performance of GNSS such as GPS and GLONASS, both of which are supported by Swift’s receivers.
SBAS support is particularly relevant for Swift customers located in places where cell phone coverage is sparse or is not available, such as rural areas where precision agriculture operations are taking place or alternatively in marine locations, lakes, in-land waterways and up to approximately 100 miles off shore where cellular or internet coverage may not be feasible.
Applications using SBAS do not require a local reference station, allowing rovers such as drones, combines and other agricultural equipment and marine vessels to benefit from satellite corrections accurate to a sub-meter, when centimeter-accuracy is not required and where internet or cell coverage is spotty or absent.
SBAS Support — The new firmware adds support for WAAS + EGNOS + MSAS + GAGAN regional satellite constellations and augments standard positioning performance for GLONASS (G1/G2) + GPS (L1/L2C) for use with Swift Navigation products.
Acquisition Improvements — Firmware 1.5 allows Piksi Multi and Duro a faster time to first fix and once a signal has been acquired, improves accuracy and availability. Time to first RTK fix was improved by 21 seconds.
Standard Positioning Performance (SPP) Enhancements — Time to first SPP improved by 7 seconds.
Increased Satellite Count for RTK — Increased satellite count used in the RTK engine improves RTK performance in all environments, particularly those where skyview is partially obscured and/or rapidly changing.
“The addition of four regional satellite constellations for our devices enhances reliability and improved position accuracy in challenging or remote environments where autonomous vehicles may have limited or no cell coverage. Essentially, SBAS provides a free corrections service, allowing our precision agriculture, marine and other customers to receive satellite corrections without a base station,” said Anthony Cole, Ph.D., director of the measurement and positioning team at Swift Navigation. “Being hardware-ready means that Piksi Multi and Duro users simply download the 1.5 firmware at no additional cost, to get the latest features and performance improvements.”
Geneq has launched the SXblue Premier GNSS receiver, which is available in a submetric version (GNSS) or centimetric version (real-time kinematic, RTK).
The new SXblue Premier GNSS receiver is equipped with the Pacific Crest Maxwell 6 Trimble technology with BD910 (GNSS version) and BD930 (RTK version) OEM boards, delivering 220 channels to acquire and track GNSS signals from all constellations in view. It makes effective use of GPS, GLONASS, Galileo, BeiDou, QZSS and SBAS signals for outstanding highly precise positioning.
The SXblue Premier is small and light weight, and rugged for field work. It is equipped with dual mode for Bluetooth V2.1 and Bluetooth V4.0, ensuring the unit’s wireless communication with any Android or Windows terminal. With its two models, the user will have large efficiency and flexibility on the field either with SBAS corrections or RTK reference networks.
In addition, SXblue Premier can be configured for Wi-Fi hotspots, allowing users to connect and access a web management platform. It also can be used as a data link, providing a quick connection to the internet to receive corrections from reference station (CORS) networks so that it can process RTK measurements.
With its internal memory using an 8-GB solid state disk, SXblue Premier provides enough storage space for field data collection or raw data recording for a high data sampling rate.
Multiple compatible software programs — including FieldGenius, Carlson, Collector for ArcGIS — will meet the users’ diverse need, making SXblue Premier more powerful and flexible.
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.
EGNOS V3 will offer improved and secure Civil Aviation Safety of Life services for the next decade over Europe. The program will ensure a full continuity of service and will be the first operational SBAS using both GPS and Galileo.
Airbus has been selected by the European Space Agency (ESA) as the prime contractor to develop EGNOS V3, the next generation of the European Satellite Based Augmentation System (SBAS) planned to provide the civil aviation community with advanced safety-of-life services and new services to maritime and land users.
Developed by ESA on behalf of the European Commission and the European GNSS Agency (GSA), EGNOS V3 (European Geostationary Navigation Overlay Service) will provide augmented operational safety-of-life services over Europe that improve the accuracy and availability of user positioning services from existing GNSS (Galileo and GPS).
EGNOS also provides crucial integrity messages to EGNOS users with alerts within a few seconds in case of system degradation, consolidating EGNOS’ position as one of the leading edge GNSS systems in the future.
Besides improved safety-of-life services, EGNOS V3 will improve robustness against increasing security risk, in particular cyber-security risks.
EGNOS V3 will ensure a full continuity of service for the next decade and will be the first operational SBAS implementing the dual-frequency and multi-constellation world standard, with both GPS and Galileo, replacing EGNOS V2 which has been in operation since 2011.
“This programme is strategic for Airbus to strengthen our position in the Navigation field. The signature of this contract is the result of more than 5 years of intense team work and investment,” said Nicolas Chamussy, head of Space Systems at Airbus. “With our consortium, we bring a large pool of resources and experience in Europe covering the successful development of critical and secure ground segment. I am confident that we will make EGNOS V3 a success story.”
As prime contractor, Airbus will be leading a consortium with partners from France, Germany, Spain and Switzerland. Airbus will be responsible for the development, integration, deployment and preparation of EGNOS V3 operations, the overall performance of the system and the Central Processing Facility, which is the heart of the real-time navigation algorithms.
During the 6.5-year contract, around 100 people and 20 subcontractors will work on delivering the EGNOS V3 system. In 2023, the single-frequency version will be available to replace the current operational version and, 18 months later, the final version in dual frequency will be delivered.
EGNOS is composed of a large network of about 50 ground stations deployed over Europe, Africa and North America, two master control centers near Rome and Madrid, and a System Operation Support Centre in Toulouse. EGNOS will also use geostationary satellite navigation payloads.
By Changfeng Yang, Chief Architect of BeiDou Navigation Satellite System
Changfeng Yang
As one of the four major GNSS providers, the establishment of BeiDou Navigation Satellite System (BDS) has been steadily developed, following a three-step strategy. By around 2020, BDS will form a nominal space constellation consisting of 30 satellites, including three satellites in geostationary Earth orbit (GEO), three satellites in inclined geosynchronous satellite orbit (IGSO) and 24 satellites in medium Earth orbit (MEO). It will provide global users with open and high-quality services free of charge, including navigation, positioning, timing, short message communication, search and rescue and so on.
BDS is aimed at developing into a world-class global navigation satellite system, with innovative and advanced technologies, extraordinary user experience, international development and worldwide presence, which can provide fundamental time and space reference for national defense and economic-social development, and advance the progress of high-tech and IT industries.
BDS has initiated several innovative attempts in the fields of both international satellite navigation and domestic aerospace for the first time, and paved a unique development path of a satellite navigation system, with an eye on the state conditions and distinctive features. On Jan. 9, 2017, the BD-2 Project won the top National Scientific and Technological Progress Award. In 2017, BDS achieved fruitful results in the aspects of system construction, integrated applications and international development.
System Construction
Through upgrading and reconstructing the ground system, the service performance, stability and availability of the BD-2 constellation have been improved. To achieve user-oriented services, the updated Interface Control Document (ICD) for B1C and B2a open service signals (Version 2.1) was released in accordance with the constellation change.
The international GNSS Monitoring and Assessment System (iGMAS) has been built, consisting of eight domestic monitoring stations and 16 overseas stations, to monitor and assess the service performances of BDS, GPS, GLONASS and Galileo at real-time worldwide. It has taken all factors into consideration, including constellation status, signal-in-space, navigation message, service performance and high-precision products, and so on. According to its analysis results, the nominal positioning accuracy of the BD-2 system in the coverage area has been optimized from 10 meters to 8 meters.
Development of the BD-3 System. On Nov. 5, the first pair of the 24 BD-3 MEO satellites were successfully launched, while another pair is planned to be launched by the end of the year.
Liftoff of the first pair of the BD-3 MEO satellites on Nov. 5, 2017. (Credit: Xinhua)
The BD-3 satellites are equipped with B1C and B2a signals with optimized performance, which are compatible and interoperable with other GNSS signals. The interface control document of B1C and B2a signals (beta version) was released in September. The BD-3 satellites also adopt the higher-performance rubidium atomic clock with stability of E-14 and hydrogen atomic clock with stability of E-15. By utilizing new technologies, the signal-in-space (SIS) accuracy will be superior to 0.5 m; the position accuracy will be doubled or quadrupled, and reach 2.5 m to 5 m.
The BD-3 system will retain the short message communication service of its predecessors, and further enhance basic positioning, navigation and timing (PNT) service capabilities. Satellite-based augmentation system (SBAS) and search-and-rescue (SAR) services will be added and developed according to international standards.
After in-orbit tests and networking validation, the BD-3 satellites will be able to provide operational services, and accelerate the global coverage of BDS.
Ground-Based Augmentation. The Phase I construction of the BDS/GNSS ground-based augmentation system has been completed, consisting of 150 framework reference stations, 1,200 reference stations of higher density network, national data processing center, six industrial data-processing centers, and manufacturing of user terminals. This system has achieved basic service capabilities, and its service performance standard (version 1.0) has been released. Through integration with the internet, a cloud platform has been established to provide high-precision space-time information services, including real-time navigation services at meter-level and decimeter-level, as well as precise positioning services at centimeter-level and millimeter-level.
Satellite-Based Augmentation. Based on the International Civil Aviation Organization (ICAO) standards, system demonstration and validation work on the BeiDou Satellite-Based Augmentation System (BDSBAS) has been completed, and the technical status of the system has been confirmed in accordance of the next-generation SBAS Dual Frequency Multiple Constellation (DFMC) standards.
Integrated Applications
Currently, a great number of independent, self-controlled intellectual property rights on the fundamental BDS products have been achieved. World-class, advanced technologies have been developed. With the release of the first Chinese in-house developed meter-level fast positioning BDS chip, BDS applications have begun to embrace the era of meter-level positioning.
In 2017, the sales volume of BDS navigation chips and modules exceeded 50 million pieces, and that of high-precision surveying boards and navigation antenna captured 30% and 90% of market shares respectively. There are more than 14,000 enterprises (including more than 50 publicly listed companies), and more than 450,000 employees in China engaging in BDS-related business.
The annual output value of the publicly listed company in 2017 is more than RMB 50 billion (US $7.53 billion). The number of terminals produced by domestic enterprises surpasses 40 million pieces/sets. BDS has gained recognition from mainstream chip producers such as Qualcomm, Trimble, Hemisphere GNSS, Huawei, Samsung, u-blox, MTK, Broadcom, NovAtel and more, and the total number of terminals is estimated to surpass 300 million pieces or sets.
BDS continues to:
promote integrated applications and development of related industries;
bring GNSS high-precision services in combination with cloud computing, Internet of Things, big data and other technologies;
push forward the integration between BDS-related industries and high-end manufacturing, software, and integrated data industries.
BDS has been applied in the transportation, logistics, emergency rescue, marine fishing and other fields, which has greatly improved production efficiency, reduced resource consumption, and lowered pollution. For example, benefiting from the BDS applications in traffic management industry, the number of major accidents has decreased by 46.7%, and the death toll has been reduced by 48.9%. With BDS-based maritime applications, more than 10,000 lives have been saved.
BDS/GNSS augmentation services have been applied to precision agriculture, land mapping, monitoring on deformation and displacement of large-scale public facilities, and earthquake and geological hazard measurement and survey; the latter has provided important monitoring for public safety. As a result, the production of precision agriculture has increased by 5%, and the oil consumption by agricultural machinery has decreased by 10%. The time for surveying and mapping of national land is shortened from a few days to several seconds.
BDS has been fully put into mass applications. BDS-based navigation services have been adopted by various enterprises, such as Huawei, ZTE, Baidu, Autonavi, Alibaba, JD and others in the fields of manufacturing of mobile and smart terminals, location-based services (LBS), e-commerce, and so on. BDS-based LBS have been widely applied in the mass consumption sector and people’s livelihood, and many innovative applications have emerged, such as caring for seniors and children, shared vehicles, BDS-based logistics, and so on, which have been changing people’s lives and providing more convenience for the public.
International Development
At present, BDS has covered more than 50 countries and more than 3 billion people. BDS-related products have gained access to the markets of more than 70 countries and regions, more than 30 of which are along the (land-based) Belt and (maritime) Road (in line with the Belt and Road Initiative). Through joint applications with other compatible navigation satellite systems, BDS provides global users with diversified choices for better application experience.
Meanwhile, the iGMAS has contributed to the implementation of the Asia-Pacific Space Cooperation Organization project, iGMAS-International GNSS Service Pilot experimental project, and Sino-Russian monitoring and assessment cooperation, and has provided GNSS users with authentic third-party assessment results. China continuously pushes forward BDS to be recognized by the ICAO, International Maritime Organization (IMO), mobile communication standard Partnership Project and other organizations, to serve the world in line with international conventions.
In October, three PRN codes which are essential to the development of BDSBAS were assigned; the SBAS service provider identifier and UTC standard identifier have been assigned to BDSBAS by ICAO, which marks BDSBAS an official SBAS provider in the ICAO family, and lays the foundation for the follow-up construction of BDSBAS, as well as its provision of standard navigation services for the civil aviation sector.
In March, a multi-system (including GPS, BDS and GLONASS) ship-borne receiver standard was approved by the IMO. BDS has also been included in the PNT guidelines of maritime applications.
In the field of mobile communication, 26 technical standards that support the BDS positioning function have been adopted by the third- and fourth-generation mobile communication standard Partnership Projects.
Future Plans
BDS will keep improving its continuous stability and service accuracy. Two more BD-2 replacement satellites will be launched in 2018, ensuring its regional service performance will be remain stable and be enhanced.
Eighteen BD-3 MEO satellites and one BD-3 GEO satellite will be launched by around the end of 2018. Upon the deployment of those 19 satellites, BD-3 will possess the initial operational capability and serve the countries along the Belt and Road. The official version of ICD for B1C and B2a open service signals, as well as other system documents, will be released, in line with the operational status of BD-3 satellites, for the convenience of public applications.
In regard to augmentation systems, China plans to complete the construction of Phase II BDS/GNSS ground-based augmentation system in 2018, and advance the recognition of BDS-based high-precision services as public goods. In 2018, the first BDSBAS GEO satellite with the BDSBAS payload will be launched to start the deployment of the BDSBAS system.
In terms of applications and international development, China will give full play to the role of BDS in the integration procedure between industrialization and IT applications, to promote the development of information industry, adjustment and upgrading of industrial structure.
China will also strengthen the cooperation and communication with other navigation satellite system providers, carry out coordination under the framework of international organizations and multilateral platforms, improve the international development of BDS, provide better services for users along the Belt and Road, and expand BDS services to serve users worldwide.
