GPS World

Tag: QZSS constellation

  • Septentrio’s Stellar 2022

    Septentrio’s Stellar 2022

    Receiver maker Septentrio, based in Leuven, Belgium, has made a series of announcements this year that push the industry forward, from updating existing receivers to accepting new services to launching new product lines.

    Head of the CLAS

    In March, the company launched three new products that support Japan’s high-accuracy Centimeter Level Augmentation Service (CLAS). CLAS, which receives the L6 signal, transmits high-accuracy corrections from Japan’s QZSS constellation. The technology was developed in close cooperation with CORE, a leading integrator of high-accuracy positioning technology and services in Japan.

    Photo: Septentrio
    Photo: Septentrio

    Septentrio now offers the mosaic-CLAS receiver for high-volume industrial applications; the AsteRx-m3 CLAS that combines PPP-RTK CLAS with dual-antenna heading functionality; and the AsteRx SB3 CLAS in a ruggedized IP68 enclosure to protect it in harsh environments.

    Septentrio is simultaneously offering various receiver types to the Japanese market ensuring an optimal match between products and customer needs in various applications including robotics, precision agriculture, construction, machine control and UAV.

    Stopping the Spoofs

    Following the CLAS upgrade, the mosaic line received another boost in April, when Septentrio announced Open Service Navigation Message Authentication (OSNMA) functionality. OSNMA offers end-to-end authentication on Galileo’s civilian signals, protecting receivers from OSNMA attacks.

    For the past two years, Septentrio has been working closely with the European Space Agency (ESA) during the test phases of OSNMA deployment. The know-how gained during this period allowed Septentrio to be one of the first to market with this advanced security feature.

    OSNMA’s anti-spoofing capability complements Septentrio’s Advanced Interference Mitigation (AIM+) technology and further strengthens the overall security of Septentrio GNSS receivers, making them suitable for assured PNT solutions as well as critical infrastructure, such as 5G network synchronization.

    Vertical Markets

    Machine Control. In April, Septentrio launched the AsteRx-U3 ruggedized GNSS receiver, successor to the AsteRx-U for construction, mining and other machine control applications. The new receiver combines Septentrio’s latest triple-band precise positioning GNSS core with extended wireless communication features including Wi-Fi, UHF and 4G LTE. The versatile connectivity features of this receiver make it easy to fit it into any control system and enable simple and cost-effective overall design.

    Photo: Septentrio
    Photo: Septentrio

    Unmanned Aerial Vehicles (UAVs). Also in April, Septentrio is collaborating with MicroPilot, maker of professional UAV autopilots. Septentrio receivers, including the small form factor mosaic modules, as well as the OEM board AsteRx-m3, will support seamless integration of positioning and orientation into MicroPilot’s autopilot ecosystem. MicroPilot chose Septentrio GNSS receivers for their resilience to radio interference such as jamming and spoofing, as well as security and robustness with high-accuracy real-time kinematic (RTK) positioning.

    Marine. In May, Septentrio introduced the housed AsteRx-U3 Marine and the OEM board AsteRx-m3 Fg, two receivers for dredging, marine construction and offshore applications. Both offer accurate positioning near shore and offshore via centimeter-level real-time kinematic (RTK) or the built-in Fugro precise point positioning (PPP) sub-decimeter subscription service, delivered either over NTRIP internet or over L-band satellite.

    Corrections delivered over L-band allow dredging, bathymetry or marine construction projects even in areas where there is no internet service. The AsteRx-U3 Marine receiver, enclosed in an IP68-rated housing, offers a dedicated L-band demodulator with a separate L-band RF input, which allows for the use of dedicated antennas for excellent reception of L-band signals even at high latitudes.

  • Advancing the A in PTA

    Advancing the A in PTA

    Matteo Luccio
    Matteo Luccio

    The May 4-5 meeting of the National Space-Based Positioning, Navigation and Timing Advisory Board focused on its mantra to “protect, toughen and augment” (PTA) GPS. The meeting included three great presentations that bear directly on the A of that mantra.

    CAST

    The electric grid used to be simpler: regional operators flowed power unidirectionally from stations to customers basing the load on past usage. Now, the grid is becoming a wide-area network — with regional inter-connects, multi-directional flows, and load based on real-time data and predictive analysis, requiring sensors time-synchronized within 1 microsecond from UTC. Yet, this critical infrastructure’s timing applications depend entirely on vulnerable GPS technology.

    “If we can provide an authoritative, trusted synchronization source across the interconnected grid, its operators have a much better opportunity to understand the interdependencies and movement of power across their networks,” said Carter Christopher of Oak Ridge National Laboratory. He described the lab’s Center for Alternate Synchronization and Timing (CAST), which provides a redundant and resilient satellite-based service backed up by a network of terrestrial master clocks. CAST is precise, traceable and secure from jamming, spoofing, cyberattacks and physical attacks.

    HARS

    Attila Komjathy and Larry Romans of NASA’s Jet Propulsion Laboratory (JPL) proposed a GPS high-accuracy and resilience service (HARS) based on global differential GPS (GDGPS). It would provide corrections to GPS orbit and clock errors, and encrypted navigation data bits over the internet. It would match Galileo in accuracy, they said, pointing out that Galileo, QZSS and BeiDou provide high-accuracy services in their broadcast signals. HARS would improve the accuracy of consumer GPS receivers of 3–5 m to 1 m and help ensure that multi-constellation GNSS chips would continue to rely on GPS first.

    HARS could be implemented by having commercial providers—such as Apple, Google and cellular carriers—distribute GDGPS corrections generated by JPL and supported by government partners. Private industry, Komjathy and Romans pointed out, provide service for RTK, centimeter and decimeter apps, but only governments (the U.S. Coast Guard’s DGPS service and Galileo’s HAS) provide corrections for about one-meter accuracy. Therefore, HARS would not compete with industry and would create additional opportunities for it to create value-added products.

    αPNT

    David Castiel and Cyrus Langroudi, of Virtual Geosatellite LLC, proposed αPNT, a virtual geostationary satellite system with elliptical orbits that would provide active PNT in a distributed architecture integrated with a blockchain. The system, they said, would be able to provide very accurate geographical position, precise timing and guidance with a minimum number of satellites on the horizon. It would rely on two-way links between transceivers and satellites to protect against jamming or spoofing.

    While GPS’s success makes it a critical and ubiquitous infrastructure, its vulnerabilities require and stimulate exciting new R&D. Stay tuned.

  • New Septentrio receivers support Japan’s CLAS

    New Septentrio receivers support Japan’s CLAS

    The mosaic-CLAS GNSS module. (Photo: Septentrio)
    The mosaic-CLAS GNSS module. (Photo: Septentrio)

    Septentrio, a leader in high-precision GNSS positioning solutions, has launched three new products that support Japan’s high-accuracy Centimeter Level Augmentation Service (CLAS).

    The three multi-frequency GNSS receivers support CLAS on a single device, thanks to the latest GNSS technology which receives the L6 signal, which transmits high-accuracy corrections from Japan’s QZSS constellation. This technology was developed in close cooperation with CORE, a leading integrator of high-accuracy positioning technology and services in Japan.

    • The mosaic-CLAS receiver is a GNSS module with a very small form-factor suitable for high-volume industrial applications.
    • The AsteRx-m3 CLAS is Septentrio’s best-in-class OEM board combining PPP-RTK CLAS with dual-antenna heading functionality.
    • The AsteRx SB3 CLAS features a ruggedized IP68 enclosure to protect it in harsh environments.

    Septentrio is simultaneously offering various receiver types to the Japanese market ensuring an optimal match between products and customer needs in various applications including robotics, precision agriculture, construction, machine control and UAV.

    “We are very pleased to jointly develop CLAS software on a new GNSS module, mosaic-CLAS,” emphasized Takahiro Yamamoto, director, GNSS Solution Business Center at CORE Corp. “This receiver puts CLAS GNSS technology on par with regular RTK receivers in terms of size as well as price. We believe that the realization of CLAS on the Septentrio mosaic platform will significantly promote the use of new QZSS services for industrial applications.”

    “The launch of our new module and OEM board with CLAS support opens up new markets and use cases, which will benefit from centimeter-level positioning with fast acquisition time,” commented François Freulon, head of Product Management at Septentrio. “This launch demonstrates the technological leadership of Septentrio and our ability to provide dedicated solutions embedding L6 bands for the Japanese market.”

    The CLAS PPP-RTK is the latest generation of GNSS correction services, combining near-RTK accuracy and quick initialization times with the broadcast nature of PPP. Receivers with built-in CLAS functionality offer sub-decimeter positioning accuracy right out of the box. Corrections for high-accuracy positioning are received directly from satellites, reducing the need for additional base stations or service subscriptions.

    Find out more about PPP-RTK and other positioning correction methods in the insight article GNSS Correction Demystified.

  • First transmission of L1C/B by QZS-1R

    First transmission of L1C/B by QZS-1R

    QZS-R1 is prepped for testing. At left is the Earth-oriented surface that hosts the L-band antenna. (Photo: JAXA)
    QZS-R1 is prepped for testing. At left is the Earth-oriented surface that hosts the L-band antenna. (Photo: JAXA)

    By Peter Steigenberger, Steffen Thoelert, Sergei Yudanov and Markus Ramatschi

    The Japanese QZS-1R satellite was launched on Oct. 26, 2021, from the Tanegashima Space Center in Japan. It serves as a replenishment for QZS-1, the first spacecraft of the Japanese Quasi-Zenith Satellite System (QZSS) in orbit since September 2010.

    QZS-1R joins the current QZSS constellation of three satellites in inclined geosynchronous orbit (IGSO) and one geostationary satellite. These four Block I satellites transmit the L1C/A signal at 1575.42 MHz.

    QZS-1R, as well as future QZSS satellites, are able to transmit the new L1C/B signal. L1C/B is based on the same family of gold codes as L1C/A, but uses a binary offset carrier (BOC) modulation instead of the binary phase-shift keying (BPSK) and a different PRN range (203–206).

    Compared to BPSK, the BOC modulation adds a square wave subcarrier with a frequency of fsc = 1.023 MHz that equals the chipping rate of the ranging code. This subcarrier shifts the peak spectral energy from the center frequency fL1 to fL1 ± fsc to reduce interference with the GPS L1C/A signals.

    During in-orbit testing (IOT) from late November until early December 2021, QZS-1R transmitted L1C/A and L1C/B signals intermittently. FIGURE 1 shows a spectrum of the L1-band transmissions of QZS-1R recorded on Nov. 25 with the 30-meter dish antenna of the German Space Operations Center in Weilheim, Germany, as well as a spectrum of QZS-2 recorded in July 2017.

    Figure 1. L1 spectra of QZS-1R (red) transmitting L1C/B and L1C, as well as QZS-2 (blue) transmitting L1C/A and L1C. The spectra were measured with DLR’s 30-meter high-gain antenna on Nov. 25, 2021, and July 20, 2017, respectively. (Credit: DLR)
    Figure 1. L1 spectra of QZS-1R (red) transmitting L1C/B and L1C, as well as QZS-2 (blue) transmitting L1C/A and L1C. The spectra were measured with DLR’s 30-meter high-gain antenna on Nov. 25, 2021, and July 20, 2017, respectively. (Credit: DLR)

    During IOT, QZS-1R had an extremely low maximum elevation of 0.8° in Weilheim. Due to technical restrictions for such low elevations, QZS-1R had to be observed with a sidelobe of the 30-meter antenna. As a result, the respective observations are much more noisy than the QZS-2 reference data.

    Nevertheless, the different spectral characteristics of L1C/B and L1C/A can be clearly seen in FIGURE 1: L1C/B has two maxima at 1574.4 and 1576.5 MHz due to the BOC modulation, whereas the BPSK L1C/A signal has one maximum at the center frequency of 1575.42 MHz.

    GNSS receivers of the International GNSS Service (IGS) started to track L1C/A, L1C, L2C and L5 signals of QZS-1R on Nov. 17. Aside from the regular PRN code J04, test signals using the non-standard code PRN J06 were intermittently transmitted by QZS-1R during the IOT and tracked by these receivers.

    Based on the public specification of the new L1C/B signal, Javad GNSS developed a prototype firmware that enabled tracking of this signal during the early transmissions. This firmware was installed on a Javad TRE-3 receiver operated by GFZ German Research Centre for Geosciences at its IGS station WUH200CHN in Wuhan, China.

    FIGURE 2 illustrates the noise and multipath characteristics of different QZS-1R pseudorange measurements. It is based on the so-called multipath linear combination of L1 pseudorange and L1/L2 carrier-phase observations covering a six-hour data arc. RMS values were computed for 5-degree elevation bins for each pseudorange signal. While the individual signals were tracked on different days of the IOT and the associated results have to be interpreted with care, the data indicate a very similar ranging performance of the legacy C/A signal and the new C/B signal. Best results are obtained with the L1C signal, which uses both a higher signal power and an advanced modulation with superior multipath suppression.

    Figure 2. Noise and multipath characteristics of QZS-1R signals on the L1 frequency tracked by the IGS station WUH200CHN in Wuhan, China. (Credit: DLR)
    Figure 2. Noise and multipath characteristics of QZS-1R signals on the L1 frequency tracked by the IGS station WUH200CHN in Wuhan, China. (Credit: DLR)

    QZS-1R will resume continuous transmission of L1C/A as soon as declared healthy. The transition from L1C/A to L1C/B is planned for 2023-2024, when an operational QZSS constellation of seven satellites is reached. The launches of the IGSO satellite QZS-5, the geostationary QZS-6, and the quasi-geostationary QZS-7 are all planned for 2023.

    Also see Directions 2022: Now 3 years old, QZSS hits its stride.

    Manufacturers

    GNSS data used in this article were collected with a Javad GNSS TRE-3 receiver. The spectral overviews were captured with a Rohde & Schwarz FSQ26 signal analyzer.

    Peter Steigenberger is a senior scientist at the German Space Operations Center of the German Aerospace Center (DLR), where he conducts research in the field of new satellite navigation systems.

    Steffen Thoelert is an electrical engineer at DLR’s Institute of Communications and Navigation. His research activities focus on signal-quality monitoring and satellite payload characterization.

    Sergei Yudanov is a senior firmware developer at Javad GNSS, Moscow. His main field of activity is GNSS signal processing.

    Markus Ramatschi is a senior scientist at the Helmholtz Centre Potsdam, GFZ German Research Centre for Geoscience. He is operating a global GNSS reference station network.

    Further Reading

    Cabinet Office, Quasi-Zenith Satellite System Interface Specification: Satellite Positioning, Navigation and Timing Service, IS-QZSS-PNT-004, Jan. 25, 2021.

    Ramatschi M., Bradke M., Nischan T., Männel B. (2019): “GNSS data of the global GFZ tracking network,” vol 1. GFZ Data Services. https://doi.org/10.5880/GFZ.1.1.2020.001

    Thoelert S., Hauschild A., Steigenberger P., Montenbruck O., Langley R. (2017), “QZS-2 signal analysis, QZS-3 launched.” GPS World 28(9): 10–14,