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Tag: volcanoes

  • Research Roundup: Atmospheric effects on GNSS

    Research Roundup: Atmospheric effects on GNSS

    Photo: buradaki/iStock/Getty Images Plus/Getty Images
    Photo: buradaki/iStock/Getty Images Plus/Getty Images

    GNSS researchers presented hundreds of papers at the 2022 Institute of Navigation (ION) GNSS+ conference, which took place Sept. 19–23 in Denver, Colorado, and virtually. The following five papers focused on atmospheric effects on GNSS signals. The papers are available at www.ion.org/publications/browse.cfm. 

    Addressing Scintillation Error

    Mitigating the scintillation effect at low latitude is a complex matter: several kinds of experimental data must be collected, realistic models must be developed, and, most importantly, useful real-time indices and alerts must be made available.

    The authors introduce a prototype based on a patent owned by SpacEarth Technology to address scintillation error detection and mitigation, supporting precision GNSS-based services at low latitudes in any season and space weather conditions. The patent relates to a method of total electron content (TEC) and scintillation empirical forecasting, in particular short-term forecasting (seconds to minutes). The output of the method is necessary to feed mitigation algorithms aiming at improving accuracy on GNSS precise positioning techniques (RTK, NRTK, and PPP) under ionospheric harsh conditions.

    The prototype is designed with a Central Elaborating Facility, which collects the data provided by a network of GNSS monitoring stations detecting scintillation events, and broadcasts foreseen scintillation parameters. Users with a rover mitigation device can apply the parameters from the central facility for scintillation error mitigation. 

    Vincenzo Romano, INGV and SpacEarth Technology; Claudio Cesaroni, INGV; Luca Spogli, Alessandro Fiorini, INGV and SpacEarth Technology; Marco Fermi, Gter; Lorenzo Benvenuto, Gter and University of Genoa; Tiziano Cosso, Gter; Marcin Grzesiak, SRC/PAS; Joao Francisco Galera Monico, Italo Tsuchiya, UNESP; Gabriel Oliveira, Marcos Guandalini; “Ionospheric Scintillation Mitigation at Low Latitude to Improve Navigation Quality.”

    Ring of Fire GUARDIAN 

    Commonly, natural hazards release energy into the Earth’s atmosphere in the form of acoustic-gravity waves, which propagate up to the ionosphere. The resulting traveling ionospheric disturbances (TIDs) can be detected using GNSS signals, through the computation of the integrated total electron content (TEC) along the lines of sight between GNSS receivers and satellites. The global distribution of ground-based GNSS receivers constantly tracking multiple GNSS constellations (GPS, Galileo, GLONASS, BeiDou, and others) provides excellent spatio-temporal coverage around the world, including in areas of limited coverage by existing warning systems.

    The authors present the operational GNSS-based Upper Atmospheric Real-time Disaster Information and Alert Network (GUARDIAN). Based on dual-frequency GNSS data from the Global Differential GPS (GDGPS) network of the Jet Propulsion Laboratory, the GUARDIAN architecture computes slant TEC time series in near real time.

    As part of the GDGPS network, 78 stations around the Pacific ring of fire monitor the four GNSS constellations: GPS, Galileo, GLONASS and BeiDou. Cycle slips are corrected and the time series are filtered, both in real time. The resulting data stream is output live to a user-friendly public website, benefitting the general public and the scientific community. 

    The current GUARDIAN focuses on the Pacific region. However, the architecture can readily be extended to a worldwide coverage.

    Léo Martire, S. Krishnamoorthy, L. J. Romans, B. Szilágyi, P. Vergados, A. W. Moore, A. Komjáthy, Y. E. Bar-Sever, A. B. Craddock, NASA Jet Propulsion Laboratory, California Institute of Technology; “GUARDIAN: A Near Real-Time Ionospheric Monitoring System for Natural Hazards Early Warnings.”

    Civil Aviation Interference

    The authors provide a survey on GNSS receiver architectures with emphasis on new carrier-tracking techniques for mitigating the adverse effect of ionospheric scintillation within the context of civil aviation. The survey is complemented by results gathered from simulations on the impact of ionospheric scintillation in conventional receiver architectures. A review on scintillation mitigation techniques is carried out, covering several “technique families,” highlighting their potential for performance improvement, as well as their shortcomings and challenges in implementation.

    A semi-analytical simulation campaign is carried out for different modulations: L1, L5 for GPS, and E1, E5a for Galileo. Here, the performance of a standard receiver tracking a set of GPS and Galileo satellites affected by ionospheric scintillation is analyzed to pinpoint existing vulnerabilities to this effect.

    The simulation results show that ionospheric scintillations are responsible for large variations in carrier-to-noise ratio, which in turn can be responsible for losses of lock and large phase variations, increasing phase RMSE and in some cases leading to cycle slips of the phase estimation. Thus, the adopted solution must be robust to signal power fluctuations and the occurrence of cycle slips and able to maintain phase lock.

    António Negrinho, GMV-PT Pedro Boto, GMV-PT Marta Cueto, GMV-ES Mikael Mabilleau, EUSPA Claudia Paparini, EUSPA Ettore Canestri, EUSPA; “Survey on Signal Processing Techniques for GNSS Ionospheric Scintillation Mitigation.”

    Tonga Eruption Data Analyzed

    Extreme natural disasters, such as volcanic eruptions, can create visible pressure waves in the atmosphere and trigger observable ionospheric wave responses that can travel hundreds of kilometers in the ionosphere. The acoustic and gravity waves generated can cause ionospheric TEC perturbations and variations. The TEC determines the GNSS ionospheric delay and can cause significant positioning errors, which may affect the performance of GNSS-based applications.

    The researchers processed GNSS data collected from the Hong Kong Satellite Positioning Reference Station Network to analyze the ionospheric activity and positioning performance responding to the Tonga volcanic eruption on Jan. 15, 2022. To detect and repair cycle-slip jumps, the researchers applied theTEC rate and Melbourne Wubbena Wide Lane (MWWL) linear combinations. A Savitzky-Golay low-pass filter with a 30s window was used to improve the TEC accuracy.

    The team investigated the changes in TEC, Rate of TEC index (ROTI) and positioning errors in the eastward, northward and upward directions after the anomalous ionospheric propagation to Hong Kong between 11:30 and 14:30. The team found the ionospheric anomaly could generate large changes in the three parameters, with peaks up to three times the calm period. Their prompt research contributes to a better understanding of the coupling of extreme ionospheric activities and dynamics caused by volcanic eruptions. 

    Xiaojia Chang, Kai Guo, Zhipeng Wang, Kun Fang, Hongxia Wang, Beihang University; Hailong Chen, China Academy of Aerospace Electronics Technology; “Ionospheric Anomaly and GNSS Positioning Responses to the January 2022 Tonga Volcanic Eruption.” 

    Toolbox for Monitor Network

    The MONITORtoolbox is a set of Python-coded software tools to perform automatized large-scale processing of data from the Monitor network of the European Space Agency (ESA). The Monitor network aims to continuously monitor ionospheric scintillation events from multiple ground stations strategically located around the globe. It accommodates a repository with a large number of GNSS measurements containing scintillation events for users to analyze scintillation data or for research purposes.

    This paper shows the potential of the MONITORtoolbox for providing access to a large amount of data that otherwise, without a systematic processing, becomes practically useless. The software developed implements the means to collect data and store it in a local database for quick offline access. It detects the presence of scintillation events based on certain conditions and criteria defined by the user and identifies its properties in terms of duration, time of occurrence, intensity and satellite location. It implements the tools to compute relevant statistics, providing insights on ionospheric scintillation phenomena.

    Sergi Locubiche-Serra, Alejandro Pérez-Conesa, Diego Fraile-Parra, Gonzalo Seco-Granados, José A. López-Salcedo, Universitat Autònoma de Barcelona, IEEC-CERES; Juan M. Parro-Jiménez, Raúl Orús-Pérez, ESTEC, European Space Agency; “MONITORtoolbox — Software Tool for the Analysis of Ionospheric Scintillation Data from the ESA Monitor Network.” 

  • Research Roundup: GPS reveals volcanic activity under Europe

    Research Roundup: GPS reveals volcanic activity under Europe

    Scientists have discovered new evidence for active volcanism next door to some of the most densely populated areas of Europe. The study crowdsourced GPS monitoring data from antennae across western Europe to track subtle movements in the Earth’s surface, thought to be caused by a rising subsurface mantle plume.

    The Eifel region lies roughly between the cities of Aachen, Trier and Koblenz, in west-central Germany. It is home to many ancient volcanic features, including the circular lakes known as maars. Maars are the remnants of violent volcanic eruptions, such as the one that created Laacher See, the largest lake in the area. The explosion that created the lake is thought to have occurred around 13,000 years ago.

    The mantle plume that fed this ancient activity is thought to still be present, extending up to 400 kilometers (km) into the earth. However, whether or not it is still active is unknown. “Most scientists had assumed that volcanic activity in the Eifel was a thing of the past,” said Corné Kreemer, lead author of the new study. “But connecting the dots, it seems clear that something is brewing underneath the heart of northwest Europe.”

    An aerial view of Laacher See, a volcanic caldera lake with a diameter of 2 km in Rhineland-Palatinate, Germany. Created by volcanic activity, maars like this are also found in other parts of Europe and on other continents, but Eifel-Maars are the classic example worldwide. (Photo: bbsferrari/iStock / Getty Images Plus/Getty Images)
    An aerial view of Laacher See, a volcanic caldera lake with a diameter of 2 km in Rhineland-Palatinate, Germany. Created by volcanic activity, maars like this are also found in other parts of Europe and on other continents, but Eifel-Maars are the classic example worldwide. (Photo: bbsferrari/iStock / Getty Images Plus/Getty Images)

    In the new study, the team — based at the University of Nevada, Reno and the University of California, Los Angeles — used data from thousands of commercial and state-owned GPS stations all over western Europe. The research revealed that the region’s land surface is moving upward and outward over a large area centered on the Eifel, and including Luxembourg, eastern Belgium and the southernmost province of the Netherlands, Limburg.

    “The Eifel area is the only region in the study where the ground motion appeared significantly greater than expected,” said Kreemer. “The results indicate that a rising plume could explain the observed patterns and rate of ground movement.”

    The new results complement those of a previous study in Geophysical Journal International that found seismic evidence of magma moving underneath the Laacher See. Both studies point towards the Eifel being an active volcanic system.

    The implication of this study is that there may not only be an increased volcanic risk, but also a long-term seismic risk in this part of Europe. The researchers urge caution, however. “This does not mean that an explosion or earthquake is imminent, or even possible again in this area. We and other scientists plan to continue monitoring the area using a variety of geophysical and geochemical techniques, to better understand and quantify any potential risks.”

    GPS observations of ground movement under the Eifel area. Colors represent contoured vertical motion inferred from GPS station data, and white and black arrows indicate the direction in which the crust is horizontally stretching or compressing, respectively. The highest upward motion of ~1 mm per year is found near the Eifel volcanic field. (Image: Study authors)
    GPS observations of ground movement under the Eifel area. Colors represent contoured vertical motion inferred from GPS station data, and white and black arrows indicate the direction in which the crust is horizontally stretching or compressing, respectively. The highest upward motion of ~1 mm per year is found near the Eifel volcanic field. (Image: Study authors)

    Citation: “Geodetic evidence for a buoyant mantle plume beneath the Eifel volcanic area, NW Europe” by Corné Kreemer, Geoffrey Blewitt, Paul M. Davis. Geophysical Journal International, Volume 222, Issue 2, Aug. 1, 2020, pp. 1316–1332, https://doi.org/10.1093/gji/ggaa227

  • NASA issues volcano ash contract to Black Swift

    With a legacy of delivering reliable, robust, and highly accurate small Unmanned Aircraft Systems (sUAS), NASA has awarded Black Swift Technologies (BST), a specialized engineering firm based in Boulder, Colorado, the contract to develop and deliver a purpose-built scientific platform to explore volcanoes in order to improve air traffic management systems and the accuracy of ashfall measurements.

    BST will deliver to NASA a tightly integrated sUAS solution consisting of an airframe, avionics, and sensors specifically designed to measure selected gases and atmospheric parameters including, temperature, pressure, humidity, and 3D winds as well as more advanced measurements such as particle sizing and trace gases.

    Based on BST’s commercially available SuperSwift airframe and SwiftCore Flight Management System—which have been proven in the field to provide a cost-effective, powerful, and easy-to-operate—the SuperSwift XT [figure 1] is specifically engineered to meet the demands of high altitude flights through strong winds and damaging airborne particulates typical of nomadic scientific field campaigns in harsh environments.

    “NASA and similar scientific agencies require deliverables with a high degree of accuracy and reliability,” emphasizes Jack Elston, Ph.D., CEO of Black Swift Technologies. “The SuperSwift XT will be designed to collect data in harsh environments and will enhance the performance and utility of NASA’s Airborne Science fleet.”

    Member organizations of NASA’s Airborne Science Program can all benefit from the measurements provided by this system in various atmospheric conditions using different sensor payloads which, by design, are easily interchangeable. The sUAS will provide targeted, in situ observations from previously inaccessible regions that can significantly advance NASA’s goal of safe, efficient growth in global aviation by aiding in the collection of scientific data from which predictive Volcanic Ash Transport and Dispersion models (VATD) can be used to inform air traffic management systems.

    Leveraging BST’s proprietary Mission Planning Software, scientists can program the SuperSwift in minutes to calculate the area under review and then begin collecting data for immediate analysis and decision making. With its intuitive tab-driven interface, flight planning is simple and easy to accomplish.

    Mission monitoring and mapping is all done from a handheld Android Tablet loaded with BST’s SwiftTab software. Gesture-based controls enable users to confidently deploy their SuperSwift with minimal training while being able to collect data over geography that is topically diverse with confidence.

    The existence of a sUAS capable of carrying the necessary instruments routinely through harsh environments adds an invaluable contribution to the calibration and validation of data collected from ground- and satellite-based methods. The flight envelope, concept of operations (CONOPS), and rugged nature of the SuperSwift XT will permit researchers to collect data previously unobtainable through traditional data collection methods or existing sUAS.

    This includes gathering difficult to obtain data sets such as from volcanic plumes shortly after eruption (i.e., particle size-frequency distribution, vertical ash concentration distribution, SO₂ flux, etc.).

    The innovations of the SuperSwift XT, including the total sensor suite, can be utilized for scientific research by federal and state public agencies and other state-funded laboratories to collect data on coherent atmospheric structures such as smog, volcano plumes, wildfire smoke, chemical fires, forest humidity, etc.

    Commercial applications for private industry exist as well, such as utilizing the SuperSwift XT to assess the composition, and relative danger, of chemical fires at refineries or the chemical composition of smokestack exhaust.