GNSS scintillation: detection, forecasting and mitigation

Lead Research Organisation: University of Nottingham
Department Name: IESSG

Abstract

Although GNSS systems now underpin a significant part of modern infrastructure, such as financial markets, telecoms, power generation and distribution as well as transport and emergency services, they suffer from a number of known vulnerabilities. One such shortcoming relates to an ionospheric disturbance known as scintillation. The phenomenon of scintillation is familiar to most people through the twinkling of star light as it crosses the atmosphere. Ionospheric scintillation causes amplitude and phase variations on signals from GNSS satellites when they cross the ionised upper atmosphere (the ionosphere). Currently, GNSS receivers are not robust against radio scintillation; effects range from degradation of positioning accuracy to the complete loss of signal tracking. During scintillation events, required levels of accuracy and continuity, as well as availability, may not be met, thus compromising commercial operations, such as maritime navigation, geophysical exploration and airplane navigation during airport precision approach. The project will quantify the problem of ionospheric scintillation over the forthcoming solar maximum (2010-2013) and develop algorithms to reduce the impact on the users. The research will lead to improved GNSS receiver design that will enable robust performance of receivers that are compromised by effects of the natural environment through ionospheric scintillation.

Publications

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Andreotti M (2011) Galileo E5 AltBOC: How Good it Really is Against Ionospheric Effects? in International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS), Portland, Oregon, USA

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D'Angelo G (2015) GNSS data filtering optimization for ionospheric observation in Advances in Space Research

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Elmas Z G (2011) The impact and mitigation of ionospheric scintillation on Precise Point Positioning (PPP) in International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS), Portland, Oregon, USA

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Elmas Z G (2012) The Impact of Ionospheric Scintillation on the GNSS Receiver Signal Tracking Performance and Measurement Accuracy in General Assembly and Scientific Symposium, 2011 XXXth URSI

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Elmas Z G (2010) Using ionospheric scintillation indices to estimate GPS receiver tracking performance in EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria, p.14936

 
Description This research is about countering undesired effects that occur on signals transmitted from navigation satellites, such as those of the Global Positioning System (GPS) and of the new European Galileo system, when they cross the ionosphere on their way to user receivers on or near the Earth. The ionosphere is the charged upper layer of the atmosphere and causes refraction and diffraction of these signals. In our work we concentrated mostly on diffraction effects, which originate from 'electron density irregularities' that may be present in the ionosphere and that can cause fluctuations on the received signals - a GPS receiver will struggle to track the satellite signals and will consequently output erroneous position/navigation information. In worst case scenarios it may not even be able to track the satellites, leading to system outages. This 'irregular' behaviour of the ionosphere is more prominent in regions of low and high latitudes of the Earth, like Equatorial and Polar regions, and exacerbate during the peaks of the solar cycle. The peak of the current solar cycle took place in 2013.
Through the grant provided for this project we achieved the following developments:
• We set up a network of specialised GPS/Galileo receivers that can monitor the effects mentioned above, including stations at both high and low latitudes
• We formed a long term data base from the above network to support our research and future initiatives in this field
• We assessed the impact of the effects at user level and devised solutions to mitigate them, based in particular on the data recorded by the above specialised network
• We collaborated with researchers in Canada whereby our solutions were tested for a similar high latitude network
• We have contributed to relevant initiatives in Europe and elsewhere, through provision of data and insight, e.g. the SCAR (Scientific Committee on Antarctic Research)
• We devised new algorithms that can assist the GPS/Galileo receiver to maintain its normal performance when the aforementioned fluctuations occur
• We liaised with industry to help steer the project and transfer the knowledge acquired through the research
• With a focus on specific industrial applications we investigated the effects of solar radio bursts, which are intense radio emissions from the sun that can cause problems to commercial positioning services
• We promoted outreach activities through liaison with secondary schools in our proximity
Exploitation Route • Support positioning services providers with warning users of potential impact of the effects and with mitigating them
• Support companies that manufacture GPS/Galileo receivers with insight that can help them in designing receivers that are more robust to the aforementioned effects
• Form the background to specialist solutions dedicated to specific techniques and services addressed to different types of applications. For instance our improved navigation/positioning algorithms can be further customised to support the establishment of an infrastructure to provide high accuracy positioning in regions which are otherwise hampered by the effects that we studied
• Our research can be furthered to address the use of our solutions in a global scale, therefore expanding the benefits generated by this project
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Construction,Transport

 
Description In liaison with another project, funded by the EC, the data from our network has been used to provide ionospheric information and warnings to the wider community. Insight from our work has also supported the development of a scintillation monitor receiver by our associated industrial partners Septentrio Satellite Navigation. Our research has assisted our partners Fugro Intersite BV in understanding the effects of ionospheric and solar related events on their services and help mitigate them. Our work has continued to support collaboration with new partners, e.g. our joint work with Telespazio in the frame of the Ionospheric Prediction Service project funded by the EC.
Sector Agriculture, Food and Drink,Other
Impact Types Societal,Economic

 
Description EC GROW.J2 - Ionospheric Prediction Service procurement contract
Amount € 95,000 (EUR)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 02/2016 
End 01/2018
 
Description Enterprise Fellowship
Amount £24,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 01/2012 
End 09/2012
 
Description FP7 Galileo 2011 GSA 1a
Amount € 170,000 (EUR)
Funding ID GA 287201 
Organisation European Global Navigation Satellite Systems Agency (GSA) 
Sector Public
Country Czech Republic
Start 11/2012 
End 02/2015
 
Description FP7 Marie Curie Initial Training Network
Amount € 725,000 (EUR)
Funding ID 264476 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 02/2011 
End 01/2015
 
Description FP7 Space Call
Amount € 109,000 (EUR)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 02/2014 
End 07/2017
 
Description Innovative Training Networks (ITN) Call: H2020-MSCA-ITN-2016
Amount € 3,400,000 (EUR)
Funding ID 722023 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 01/2017 
End 12/2020
 
Title UK, Norway and Mediterranean ionospheric TEC and scintillation data base 
Description Continuously recorded GNSS ionospheric TEC and scintillation parameters and range data for 7 stations in the UK, Norway and Cyprus. Data has been recorded at high rate by specialised multi-frequency ionospheric monitoring receivers. Two of these 7 stations, one of which in the UK (Lerwick) and another in Norway (Bronnoysund) are currently not in operation and need a maintenance visit. 
Type Of Material Database/Collection of data 
Year Produced 2012 
Provided To Others? Yes  
Impact This is at the core of most of our research and has supported most of our publications. It has has also been instrumental in developing research in the same field at equatorial regions, such as in Brazil. Our data base also works as an attractive asset to the development of additional collaborations in the UK and elsewhere (e.g. Italy, Cyprus, Canada, Brazil) 
 
Description Bipolar climatology of Ionospheric Scintillation - INGV 
Organisation National Institute for Geophysics and Volcanology (INGV)
Country Italy 
Sector Public 
PI Contribution We have collaborated with the Italian National Institute for Geophysics and Vulcanology (INGV) for a number of years now. We contributed with expertise on scintillation characterisation and data from our high latitude receivers deployed in the context of this EPSRC grant.
Collaborator Contribution They contributed with their geophysics and ionospheric modeling expertise and data from their Arctic and Antarctic network of similar receivers.
Impact A paper titled "Bipolar climatology of GPS ionospheric scintillation at solar minimum" was published in a peer reviewed journal (see publications). Another paper resulted in 2015, titled GNSS data filtering optimization for ionospheric observation, and was published in Advances in Space Research. Collaboration is ongoing through joint projects (see new collaboration with Telespazio), joint proposals and further publication submissions.
Start Year 2010
 
Description CASES software receiver assessment and testing 
Organisation Atmospheric and Space Technology Research Associates
Country United States 
Sector Private 
PI Contribution We are testing the performance of their CASES receiver for use under scintillation conditions and bench marking it against competitor commercial counterparts.
Collaborator Contribution They loaned the receiver, helped us in setting it up and have provided support to our analyses
Impact No definitive outcome as yet - the receiver is still under test.
Start Year 2013
 
Description Collaboration with the Fugro Intersite BV 
Organisation Fugro
Country Netherlands 
Sector Private 
PI Contribution Fugro have been hosting one of our scintillation monitoring receivers at their premises in Bronnoysund, Norway. Also, we carried out analysis of data from the Fugro network, where ionospheric and solar related events have played a significant role on the degradation of the company's quality of service. Two research papers were published in collaboration with their R&D Manager, Dr Kees De Jong, and Geodesist Hans Visser.
Collaborator Contribution They have continuously maintained our receiver in Bronnoysund and contributed data to and helped steer our research..
Impact Two research papers were published in the Space Weather journal, where the results from the analysis were presented. This research is driving the development of real-time GNSS monitoring systems to overcome the downtime and outages that may be caused by solar radio bursts. These developments have already led to interest in these monitoring systems from a major client. Collaboration is ongoing, in particular through the submission of joint proposals to the EPSRC (2015) and the EU H2020 (2016).
Start Year 2010
 
Description GNSS tracking loops performance analysis under ionospheric scintillation - Prague 
Organisation Czech Technical University in Prague
Country Czech Republic 
Sector Academic/University 
PI Contribution Collaboration started with the Czech Technical University in Prague for the testing and validation of the open-source receiver developed by that University (Witch Navigator - http://www.witchnav.cz). The open source receiver is aimed for assessing the performance of different tracking loops under ionospheric scintillation conditions.
Collaborator Contribution They have loaned us their Witch Navigator receiver, which they installed and provided support for the tests.
Impact The receiver presented a number of issues that could not be resolved therefore the collaboration came to a halt. These issues are still being dealt with by the partners and the collaboration may resume in the future.
Start Year 2011
 
Description Ionospheric Prediction Service procurement contract led by Telespazio 
Organisation Telespazio SPA
Country Italy 
Sector Private 
PI Contribution This is an EC procurement contract led by Telespazio where the University of Nottingham is in charge of research activities in the area of prediction of GNSS receiver tracking errors, probability of signal loss of lock and user positioning error levels, as well as detection of TID (Travelling Ionospheric Disturbances). Our task will involve extensive use of the data provided by a number of GNSS receivers that were deployed under the EPSRC grant EP/H003479/1 and which are still in operation.
Collaborator Contribution Telespazio are managing the whole project and designing the prediction tools that will be implemented in the Ionospheric Prediction Service prototype. Other partners are Istitute Nazionale di Geofisica e Vulcanolgia (INGV), Nottingham Scientific Ltd, (NSL) and University of Tor Vergata (UTOV). INGV and UTOV will work in collaboration with Nottingham in the research activities, while NSL will deal with user requirements.
Impact The project kicked off Feb 2016 and therefore no outcomes exist so far.
Start Year 2015
 
Description Matching funds for Training REsearch and Applications network to Support the Ultimate Real time high accuracy EGNSS solution 
Organisation Hong Kong Polytechnic University
Country Hong Kong 
Sector Academic/University 
PI Contribution Contributor (support letter, CV and contribution to case for support) to successful application by Hong Kong Polytechnic University (Prof Wu Chen) to the European Commission (EC) / Research Grants Council (RGC) Collaboration Scheme 2016/17. This successful proposal secured match funds for HKPU to collaborate, by contributing data, expertise and joint research work, with the TREASURE project (www.treasure-gnss.eu), Feb 2017 - Jan 2021, total HK$2M (£206k).
Collaborator Contribution HKPU was in charge of writing and submitting the proposal. Collaborative work is ongoing in the frame of the TREASURE project
Impact HKPU has taken part in TREASURE's supervisory board and is contributing to the forthcoming TREASURE 1st Workshop to take place in Rome, April 2018. Further collaboration involves exchange visits between staff at both institutions and secondment of TREASURE fellows at HKPU
Start Year 2017
 
Description Mitigating Ionospheric Scintillation for GNSS Applications - PolyU 
Organisation Hong Kong Polytechnic University
Country Hong Kong 
Sector Academic/University 
PI Contribution This collaboration involves a comprehensive study on the mitigation of ionospheric effects, scintillation and TEC abnormalities in particular, for the improvement of GNSS navigation safety. The research is funded by the Hong Kong National Research Council through a grant awarded to Prof Wu Chen of the Department of Land Surveying and Geo-Informatics/The Hong Kong Polytechnic University. I am a named co-investigator in the research project and my team and I have exchanged knowledge and data with HKPU through this project. Areas where we are collaborating include: - TEC and TEC gradient modeling - Design and exploitation of a software receiver that is robust to scintillation - Long range RTK GNSS under perturbed ionospheric conditions - Improvement of the GNSS positioning stochastic model under scintillation conditions
Collaborator Contribution As part of the above grant they funded my travel to Hong Kong in Oct 2013 and the travel of Prof Wu Chen to Nottingham in July 2014. Also, data has been exchanged between us.The scientific details of the collaboration are described in the above box.
Impact The main outcome was the participation of PolyU as associated partners in the TREASURE ITN (see 'further funding') and the successful award of matching funds by PolyU under the European Commission (EC) / Research Grants Council (RGC) Collaboration Scheme 2016/17 sponsored by the Hong Kong Research Council. This award will support the continued collaboration between the University of Nottingham and PolyU for the duration of the TREASURE project.
Start Year 2012
 
Description Near Real Time Ionospheric Monitoring Using GNSS NTRIP Networks - UNESP 
Organisation Sao Paulo State University
Department Department of Cartography
Country Brazil 
Sector Academic/University 
PI Contribution This collaboration arises from mutual interest by participants in Brazil and in the UK in developing a method to estimate the ionospheric delay and its confidence level with a view to model this systematic influence on GNSS observations. It builds on the PhD work of Claudinei Aguiar carried out at UNESP under the supervision of Dr JF Galera Monico (a VS in this EPSRC grant) and aims to enable the generation of real time TEC maps using the NTRIP protocol. I traveled to Brazil to contribute in project progress meetings through the Travel Research Fund Santander Universities Scheme that I was awarded..
Collaborator Contribution Our partners have developed a near real time service for TEC estimation and monitoring in Brazil, which has been adopted by the Brazilian National Institute for Space Research (INPE). We benefited from their expertise in this particular area to assist our understanding of TEC monitoring and calibration. This is important also because TEC gradients and sudden variations can be associated with small scale irregularities on the ionosphere that can cause scintillation effects on the received satellite signals. Claudinei Aguiar also visited Nottingham funded by the same above mentioned scheme.
Impact This collaboration continued through joint application for funds to the FP7 program, whereby we were awarded the CALIBRA project grant (see www.calibra-ionosphere.net)
Start Year 2010
 
Description Real time predictions of ionospheric structures for GNSS applications - NTU 
Organisation Nottingham Trent University
Department School of Science and Technology
Country United Kingdom 
Sector Academic/University 
PI Contribution Nottingham is contributing data from the receiver network deployed under EPSRC grant EP/H003479/1 for the construction of the models to be developed by NTU and will validate the output of these models with respect to actual occurrence of ionospheric structures in northern Europe.
Collaborator Contribution NTU will develop statistical models which will be able to predict the occurrence of small scale structures that can affect GNSS based applications, by determining the relative importance of the processes causing large-scale structuring in the ionosphere. These models will also be able to predict the amount of large-scale plasma structuring which will be used for GNSS based applications. .
Impact We are working on the preparation of a joint paper where we intend to demonstrate the feasibility of method, as well as the procedures necessary for its validation. The following step will be the submission of a joint proposal to RCUK.
Start Year 2015
 
Description Scintillation forecasting at high latitudes - Paul Prikryl 
Organisation Government of Canada
Department Communications Research Centre Canada
Country Canada 
Sector Public 
PI Contribution Research collaboration with the Communications Research Centre Canada, Ottawa, Canada (Dr Paul Prikryl) combines data from the Canadian and European sectors aiming to develop a method for scintillation forecasting at high latitudes. This has led to a joint publication in a peer reviewed journal . We contributed to this papers with data and expertise. In that paper we also included analyses based on a tool developed at Nottingham that can be used to assess tracking conditions under scintillation (this tool is described in another publication, see "Impact of Ionospheric Scintillation on GNSS Receiver Tracking Performance over Latin America - Introducing the Concept of Tracking Jitter Variance Maps" in publications)
Collaborator Contribution They contributed significant and essential data from their Canadian network, and helped us in the understanding of scintillation forecasting at high latitudes.
Impact A paper was published and another is being prepared for submission shortly. The submission above mentioned resulted in a new joint publication (listed in the relevant section).
Start Year 2012
 
Title Satellite navigation system and method 
Description We proposed a novel method for the mitigation of scintillation effects at the GNSS receiver, which does not depend on any external input. This method describes the observational error modeling based on the receiver output I/Q post correlator samples. 
IP Reference GB1112336.1 
Protection Patent application published
Year Protection Granted 2013
Licensed No
Impact A mitigation strategy has been developed, which has demonstrated through testing an ability to improve positioning accuracy under scintillation conditions.
 
Description Outreach activity 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Collaboration has been established with a number of local schools in Nottingham, who have expressed an interest in communicating our field of research to their students. This has been done in collaboration with the Space Academy which promotes space based reach out activities in schools.

GPS class and a practical on mapping litter with GPS was conducted as a part of the year 9 physics classes at George Spencer Academy, Nottingham. This helped in increasing the interest from students in GCSE science.
Year(s) Of Engagement Activity 2011,2012