Options
Veettil, Sreeja Vadakke
Loading...
Preferred name
Veettil, Sreeja Vadakke
6 results
Now showing 1 - 6 of 6
- PublicationOpen AccessThe Ionosphere Prediction Service for GNSS Users(2018)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Space weather events related to solar activity can affect both ground and space-based infrastructures, potentially resulting in failures or service disruptions across the globe and causing damage to equipment and systems. Global Navigation Satellite Systems (GNSS) represent one of such infrastructures that can suffer from electromagnetic phenomena in the atmosphere, in particular due to the interaction of the RF signals with the ionosphere. The Ionosphere Prediction Service (IPS) is a project funded by European Commission to provide a prototype platform for a monitoring and prediction service of potential ionosphere-related disturbances affecting GNSS user communities. It is designed to help these communities cope with the effects of the ionospheric activity and mitigate the impacts of these effects on the specific GNSS-based application/service. The IPS development has been conceived of two concurrent activities: the design and implementation of the prototype service and the research activity, which represents the scientific backbone of IPS and is at the base of all the models and algorithms used for the computation of the products. The products are the basic IPS output that translate the nowcasting or forecasting information from the whole IPS system down to the final user. They are fine-tuned to match the different needs of the communities (scientific, aviation, high accuracy, etc.) which the service is targeted to and to warn the GNSS users about possible performance degradations in the presence of anomalous solar and atmospheric phenomena. To achieve this overarching aim, four different blocks of products dealing with solar activity, ionospheric activity, GNSS receiver and system performance figures have been developed and integrated into a unique service chain. The service is available to a set of invited users since July 2018 through a web portal and its provision with all the necessary operations will last 6 months. The prototype will be also ported to the Joint Research Centre (JRC). This phase will be useful to further test the platform, and to assess whether and how a dedicated prediction service for International Technical Symposium on Navigation and Timing (ITSNT) 2018 13-16 Nov 2018 ENAC, Toulouse, France Galileo users is to be implemented as part of the service facilities of the Galileo infrastructure.383 174 - PublicationOpen AccessThe ionosphere prediction service prototype for GNSS users(2019)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ;; ; ;; ; ;; ; ; ;The effect of the Earth’s ionosphere represents the single largest contribution to the Global Navigation Satellite System (GNSS) error budget and abnormal ionospheric conditions can impose serious degradation on GNSS system functionality, including integrity, accuracy and availability. With the growing reliance on GNSS for many modern life applications, actionable ionospheric forecasts can contribute to the understanding and mitigation of the impact of the ionosphere on our technology based society. In this context, the Ionosphere Prediction Service (IPS) project was set up to design and develop a prototype platform to translate the forecast of the ionospheric effects into a service customized for specific GNSS user communities. To achieve this overarching aim, four different product groups dealing with solar activity, ionospheric activity, GNSS receiver performance and service performance have been developed and integrated into a service chain, which is made available through a web based platform. This paper provides an overview of the IPS project describing its overall architecture, products and web based platform.466 19 - PublicationRestrictedMitigation of Ionospheric Effects on GNSS Positioning at Low LatitudesIonospheric conditions at low latitudes are extremely harsh due to the frequent occurrence ofscintillation and the presence of strong TEC gradients. For this study, the São Paulo state region in Brazil is chosenas a test area. This study presents a strategy to mitigate the ionospheric impact on RTK positioning with anexperimental result. The proposed strategy explores two approaches that can be applied simultaneously: a) tomitigate the scintillation effect on the GNSS signals by refining the stochastic model of the correspondingobservations and b) to precisely estimate the residual double difference ionospheric delay by exploiting an accurateTEC map.The strategy was tested on a long baseline kinematic processing under strong scintillation conditions (DOY21 in2014). Significant improvements were observed when the combined use of the two mitigation approaches describedabove was compared with the use of conventional state-of-the-art approaches. Copyright # 2017 Institute ofNavigation
116 5 - PublicationRestrictedAnalysis of the Regional Ionosphere at Low Latitudes in Support of the Biomass ESA Mission(2018-11)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Biomass is a spaceborn polarimetric P-band (435 MHz) synthetic aperture radar (SAR) in a dawn–dusk low Earth orbit. Its principal objective is to measure biomass content and change in all the Earth’s forests. The ionosphere introduces the Faraday rotation on every pulse emitted by low-frequency SAR and scintillations when the pulse traverses a region of plasma irregularities, consequently impacting the quality of the imaging. Some of these effects are due to total electron content (TEC) and its gradients along the propagation path. Therefore, an accurate assessment of the ionospheric morphology and dynamics is necessary to properly understand the impact on image quality, especially in the equatorial and tropical regions. To this scope, we have conducted an in-depth investigation of the significant noise budget introduced by the two crests of the equatorial ionospheric anomaly (EIA) over Brazil and Southeast Asia. This paper is characterized by a novel approach to conceive a SAR-oriented ionospheric assessment, aimed at detecting and identifying spatial and temporal TEC gradients, including scintillation effects and traveling ionospheric disturbances, by means of Global Navigation Satellite Systems ground-based monitoring stations. The novelty of this approach resides in the customization of the information about the impact of the ionosphere on SAR imaging as derived by local dense networks of ground instruments operating during the passes of Biomass spacecraft. The results identify the EIA crests as the regions hosting the bulk of irregularities potentially causing degradation on SAR imaging. Interesting insights about the local characteristics of low-latitudes ionosphere are also highlighted.1282 9 - PublicationOpen AccessA statistical approach to estimate Global Navigation Satellite Systems (GNSS) receiver signal tracking performance in the presence of ionospheric scintillationIonospheric scintillation can seriously impair the Global Navigation Satellite Systems (GNSS) receiver signal tracking performance, thus affecting the required levels of availability, accuracy and integrity of positioning that supports modern day GNSS based applications. We present results from the research work carried out under the Horizon 2020 European Commission (EC) funded Ionospheric Prediction Service (IPS) project. The statistical models developed to estimate the standard deviation of the receiver Phase Locked Loop (PLL) tracking jitter on the Global Positioning System (GPS) L1 frequency as a function of scintillation levels are presented. The models were developed following the statistical approach of generalized linear modelling on data recorded by networks in operation at high and low latitudes during the years of 2012–2015. The developed models were validated using data from different stations over varying latitudes, which yielded promising results. In the case of mid-latitudes, as the occurrence of strong scintillation is absent, an attempt to develop a dedicated model proved fruitless and, therefore, the models developed for the high and low latitudes were tested for two mid-latitude stations. The developed statistical models can be used to generate receiver tracking jitter maps over a region, providing users with the expected tracking conditions. The approach followed for the development of these models for the GPS L1 frequency can be used as a blueprint for the development of similar models for other GNSS frequencies, which will be the subject of follow on research.
184 38 - PublicationRestrictedThe Ionosphere Prediction Service(2018)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ;The aim of the Ionosphere Prediction Service (IPS) project is to design and develop a prototype platform to translate the prediction and forecast of the ionosphere effects into a service customized for specific GNSS user communities. The project team is composed by Telespazio (coordinator), Nottingham Scientific Ltd, Telespazio Vega Deutschland, the University of Nottingham, the University of Rome “Tor Vergata” and the Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV). The IPS development is conceived of two concurrent activities: prototype service design and development & research activity that will run along the whole project. Service design and development is conceived into four phases: user requirements collection, architecture specification, implementation and validation of the prototype. A sub-activity analyses also the integration feasibility in the Galileo Service center, located in Madrid. The research activity is the scientific backbone of IPS that will provide the models and algorithms for the forecasting products.111 2