## Scientific and technological production Ordered by:  Date asc. Date desc. Title asc. Title desc. Researcher asc. Researcher desc.

1 to 50 of 808 results
• Extended version. Occurrence of solar flares viewed with GPS: statistics and fractal nature

Monte Moreno, Enrique; Hernandez Pajares, Manuel
Date: 2014-09-05
Report

In this paper we describe the statistical properties of the EUV solar flux sudden variation. The solar flux variation is modeled as a time series characterized by the subsolar VTEC (Vertical Total Electron Content) double-difference in time, computed with dual frequency GNSS (Global Navigation Satellite System) measurements in the daylight hemisphere. By assuming a sudden overionization pattern of solar origin, during the last solar cycle, we propose a model that explains it's characteristics, and the forecasting limitations. The two defining characteristics of this time series, is an extreme variability (i.e.\ in a solar cycle one can find events at $400 \sigma$ from the mean value) and a temporal correlation that is independent of the time scale. We give a characterization of a model that explains the empirical results, and properties such as, a) the persistence and presence of bursts of solar flares, b) their long tail peak values of the solar flux variation. We show that the solar flux variation time series can be characterized by a fractional Brownian model for the long term dependence, and a powerlaw distribution for the extreme values that appear in the time series.

• North-south components of the annual asymmetry in the ionosphere

Gulyaeva, Tamara L.; Arikan, Feza; Hernandez Pajares, Manuel; Veselovsky, I.S.
Vol. 49, num. 7, p. 485-496
DOI: 10.1002/2014RS005401
Date of publication: 2014-07-01
Journal article

A retrospective study of the asymmetry in the ionosphere during the solstices is made using the different geospace parameters in the North and South magnetic hemispheres. Data of total electron content (TEC) and global electron content (GEC) produced from global ionospheric maps, GIM-TEC for 1999-2013, the ionospheric electron content (IEC) measured by TOPEX-Jason 1 and 2 satellites for 2001-2012, the F-2 layer critical frequency and peak height measured on board ISIS 1, ISIS 2, and IK19 satellites during 1969-1982, and the earthquakes M5+ occurrences for 1999-2013 are analyzed. Annual asymmetry is observed with GEC and IEC for the years of observation with asymmetry index, AI, showing January > July excess from 0.02 to 0.25. The coincident pattern of January-to-July asymmetry ratio of TEC and IEC colocated along the magnetic longitude sector of 270 degrees +/- 5 degrees E in the Pacific Ocean is obtained varying with local time and magnetic latitude. The sea/land differences in the F-2 layer peak electron density, NmF2, and the peak height, h(m)F(2), gathered with topside sounding data exhibit tilted ionosphere along the seashores with denser electron population at greater peak heights over the sea. The topside peak electron density NmF2, TEC, IEC, and the hemisphere part of GEC are dominant in the South hemisphere which resembles the pattern for seismic activity with dominant earthquake occurrence in the South magnetic hemisphere. Though the study is made for the hemispheric and annual asymmetry during solstices in the ionosphere, the conclusions seem valid for other aspects of seismic-ionospheric associations with tectonic plate boundaries representing zones of enhanced risk for space weather.

• Distribution and mitigation of higher-order ionospheric effects on precise GNSS processing

Hernandez Pajares, Manuel; Aragon Angel, Maria Angeles; Defraigne, Pascale; Bergeot, Nicolas; Prieto Cerdeira, Roberto; Garcia Rigo, Alberto
Journal of geophysical research B: solid earth
Vol. 119, num. 4, p. 3823-3837
DOI: 10.1002/2013JB010568
Date of publication: 2014-04
Journal article

Higher-order ionospheric effects (I2+) are one of the main limiting factors in very precise Global Navigation Satellite Systems (GNSS) processing, for applications where millimeter accuracy is demanded. This paper summarizes a comprehensive study of the I2+ effects in range and in GNSS precise products such as receiver position and clock, tropospheric delay, geocenter offset, and GNSS satellite position and clock. All the relevant higher-order contributions are considered: second and third orders, geometric bending, and slant total electron content (dSTEC) bending (i.e., the difference between the STEC for straight and bent paths). Using a realistic simulation with representative solar maximum conditions on GPS signals, both the effects and mitigation errors are analyzed. The usage of the combination of multifrequency L band observations has to be rejected due to its increased noise level. The results of the study show that the main two effects in range are the second-order ionospheric and dSTEC terms, with peak values up to 2 cm. Their combined impacts on the precise GNSS satellite products affects the satellite Z coordinates (up to +1 cm) and satellite clocks (more than ±20 ps). Other precise products are affected at the millimeter level. After correction the impact on all the precise GNSS products is reduced below 5 mm. We finally show that the I2+ impact on a Precise Point Positioning (PPP) user is lower than the current uncertainties of the PPP solutions, after applying consistently the precise products (satellite orbits and clocks) obtained under I2+ correction

• PIOM-FIPP - Experimental Campaigns Design report (ECD)

Stepniak, Katarzyna; Paziewski, Jacek; Wielgosz, Pawel; Hernandez Pajares, Manuel; Garcia Rigo, Alberto; Bosy, Jaroslaw; Hadas, Tomasz; Krypiak-Gregorczyk, Anna
Date: 2014-03-20
Report

• PIOM-FIPP - State of the Art and potential improvements in precise ionospheric, tropospheric and position estimation with GNSS

Paziewski, Jacek; Hernandez Pajares, Manuel; Garcia Rigo, Alberto; Bosy, Jaroslaw; Hadas, Tomasz; Krypiak-Gregorczyk, Anna; Wielgosz, Pawel
Date: 2014-02-03
Report

• UPC contribution to MONITOR CCN

Hernandez Pajares, Manuel; Garcia Rigo, Alberto
Date: 2014-01-27
Report

• Impact of higher order ionospheric delay on precise GNSS computation

Hernandez Pajares, Manuel; Aragon Angel, Maria Angeles; Defraigne, Pascale; Bergeot, Nicolas; Prieto Cerdeira, Roberto; Sanz Subirana, Jaime
International Colloquium Scientific and Fundamental Aspects of the Galileo Programme
p. 1-9
Presentation's date: 2013-12
Presentation of work at congresses

• UPC contribution to MONITOR Final Report

Hernandez Pajares, Manuel; Garcia Rigo, Alberto
Date: 2013-11-26
Report

• SEPsFLAREs customer requirements document and review of the state of the art for SEP forecasting (CRD_REV)

Garcia Rigo, Alberto; Hernandez Pajares, Manuel; Nuñez, Marlon; Qahwaji, Rami
Date: 2013-11-25
Report

• SEPsFLAREs Requirements Baseline - v1 (RB-v1)

Garcia Rigo, Alberto; Hernandez Pajares, Manuel; Nuñez, Marlon; Qahwaji, Rami
Date: 2013-11-25
Report

• SEPsFLAREs Solar Events Prediction system For space Launch Risk Estimation

Hernandez Pajares, Manuel; Garcia Rigo, Alberto; Nuñez, Marlon; Qahwaji, Rami; Wahab Ahmed, Omar; Ávalos, Luciano
Competitive project

• PIOM-FIPP Precise Ionospheric Modelling For Improved GNSS Positioning in Poland

Wielgosz, Pawel; Paziewski, Jacek; Bosy, Jaroslaw; Krypiak-Gregorczyk, Anna; Hernandez Pajares, Manuel; Stepniak, Katarzyna; Hadas, Tomasz; Garcia Rigo, Alberto
Competitive project

• GIM-TEC adaptive ionospheric weather assessment and forecast system

Gulyaeva, Tamara L.; Arikan, Feza; Hernandez Pajares, Manuel; Stanislawska, Iwona
Journal of atmospheric and solar-terrestrial physics
Vol. 102, p. 329-340
DOI: 10.1016/j.jastp.2013.06.011
Date of publication: 2013-09
Journal article

• New indicator for definition of ionospheric operational conditions

Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel; Prieto Cerdeira, Roberto; Schlueter, Stefan
SBAS-IONO
Presentation's date: 2013-07-12
Presentation of work at congresses

• Combination of ionospheric information

Brunini, Claudio; Azpilicueta, Francisco; Gende, Mauricio; Hernandez Pajares, Manuel; Juan, M.
International Beacon Satellite Symposium
p. 1
Presentation's date: 2013-07
Presentation of work at congresses

• North-South asymmetry in the global electron content of the Earth¿s ionosphere during solstices

Gulyaeva, Tamara L.; Arikan, Feza; Hernandez Pajares, Manuel; Veselovsky, I.S.
International Beacon Satellite Symposium
p. 1
Presentation's date: 2013-07
Presentation of work at congresses

• Definition of an SBAS ionospheric activity indicator and its assessment over Europe and Africa During the last solar cycle

Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Prieto Cerdeira, Roberto; Schlueter, Stefan
International Beacon Satellite Symposium
p. 1-4
Presentation's date: 2013-07
Presentation of work at congresses

In this work, an ionospheric activity indicator is defined based in the ¿weighted¿ Along Arc TEC rate (AATR). It is shown that this indicator, which can be easily computed from the GPS carrier phases, is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity, can be sensitive to regional behaviours of ionospheric activity

In this work, an ionospheric activity indicator is defined based in the “weighted” Along Arc TEC rate (AATR). It is shown that this indicator, which can be easily computed from the GPS carrier phases, is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity, can be sensitive to regional behaviours of ionospheric activity

• Higher order ionospheric delay effects and mitigation in GNSS signals for high precision applications

Hernandez Pajares, Manuel; Aragon Angel, Maria Angeles; Defraigne, Pascale; Bergeot, Nicolas; Prieto Cerdeira, Roberto; Sanz Subirana, Jaime; Garcia Rigo, Alberto
International Beacon Satellite Symposium
p. 1
Presentation's date: 2013-07
Presentation of work at congresses

The significance of higher order ionospheric terms (I2+) and the performance of realistic mitigation strategies are analyzed. After confirming the unfeasibility of removing second order ionospheric term (I2) with combinations of actual data of three - frequency measurements (in coincidence with the theoretical expectations), we focus on the I2+ correction modelling from electron density and geomagnetic models, and empirical bending approximations. Using realistic simulated GNSS global observations with actual geometry (by using the IRI2012 and IGRFv11 for electron density and geomagnetic field), the impact of I2+ on high precision GNSS processing has been quantified by using independently the GIPSY and BERNESE software which provides equivalent results. The main general conclusion is that the modeling of I2+ (mainly in terms of I2, the predominant term at all the elevations, and bending corrections) can mitigate most of I2+ signature in GNSS precise geodetic products (receiver position, clock and zenith non - hydrostatic delays, satellite orbits and clocks, and geocenter estimate), which, otherwise can be significant from mm to cm level during solar cycle maximum conditions. A similar conclusion can be extended consistently to Precise Point Positioning (PPP) processing.

• Outline on gAGE/UPC on-going activities in GNSS monitoring of ionosphere

Garcia Rigo, Alberto; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
International Reference Ionosphere (IRI) Workshop
p. 39
Presentation's date: 2013-06-25
Presentation of work at congresses

• Ionospheric perturbations analysis in the South East Asia Region

Garcia Rigo, Alberto; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel
International Reference Ionosphere (IRI) Workshop
p. 37
Presentation's date: 2013-06-25
Presentation of work at congresses

• MONITOR CCN - Ionospheric monitoring experimentation plan and instrument development CCN

Beniguel, Yannick; Hernandez Pajares, Manuel; Garcia Rigo, Alberto
Competitive project

• GNSS Data Processing, Vol 2: Laboratory exercises , (ESA TM-23/2, May 2013)

Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel
Date of publication: 2013-05-01
Book

This two-volume book contains a self-learning course and software tools aimed at providing the necessary background to start work in an operative way in GNSS navigation. The books are focused on the instrumental use of concepts and techniques involved in GNSS navigation and include all the elements needed to understand how the system works and how to work with it. After working through the two volumes, students should be able to develop their own tools for high-accuracy navigation, implementing the algorithms and expanding the skills learned. The first volume is devoted to theory, providing a summary of GNSS fundamentals and algorithms. The second volume is devoted to laboratory exercises, with a wide range of selected practical examples going further into the theoretical concepts and their practical implementation. The exercises have been developed with a specialised software package (the ESA/U PC gLAB educational SW, on an attached CD) and selected data files are provided for the laboratory sessions.

• GNSS Data Processing, Vol1: Fundamentals and Algorithms, (ESA TM-23/1, May 2013)

Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel
Date of publication: 2013-05-01
Book

This two-volume book contains a self-learning course and software tools aimed at providing the necessary background to start work in an operative way in GNSS navigation. The books are focused on the instrumental use of concepts and techniques involved in GNSS navigation and include all the elements needed to understand how the system works and how to work with it. After working through the two volumes, students should be able to develop their own tools for high-accuracy navigation, implementing the algorithms and expanding the skills learned. The first volume is devoted to theory, providing a summary of GNSS fundamentals and algorithms. The second volume is devoted to laboratory exercises, with a wide range of selected practical examples going further into the theoretical concepts and their practical implementation. The exercises have been developed with a specialised software package (the ESA/U PC gLAB educational SW, on an attached CD) and selected data files are provided for the laboratory sessions. This is an end-to-end GNSS course addressed to all professionals and students who wish to undertake a deeper study of satellite navigation, targeting the GNSS data processing and analysis issues.

• Feasibility of a linear model of the ionospheric scale height based on LEO GNSS occultation data

Olivares Pulido, German; Hernandez Pajares, Manuel; Aragon Angel, Maria Angeles; Sanz Subirana, Jaime
European Geosciences Union General Assembly
p. 13984
Presentation's date: 2013-05
Presentation of work at congresses

• Characterization and modelling of the ionosphere for EGNOS development and qualification

Schlüter, S.; Prieto Cerdeira, Roberto; Orús Pérez, Raul; Lam, J.P.; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel
p. 1-5
Presentation's date: 2013-04-23
Presentation of work at congresses

The availability of representative data samples, models and statistical information derived from the analysis of parameters that adequately describe the state of the ionosphere are key elements for the design, verification and qualification of EGNOS algorithms. As part of the on-going evolutions of EGNOS V2 releases, and also in support to the development of a future multi-constellation and dual-frequency SBAS (EGNOS V3), ESA has started a refinement process of the tools, data and precise definition of the ionospheric operational conditions. A particular driver for this process is the improvement of the availability performance of the current and future system especially under solar max and severe ionospheric conditions, without degradation of integrity and accuracy performances. The paper provides an overview about the concept and the data and models used for EGNOS development and qualification. It outlines the approaches to generate reference models and describes the parameter used for the characterization of nominal and perturbed ionospheric conditions from an SBAS perspective.

• Solar EUV flux rate estimation during mid and strong flares from the ionospheric electron content response signature in GNSS observations

Hernandez Pajares, Manuel; Garcia Rigo, Alberto; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Monte Moreno, Enrique; Aragon Angel, Maria Angeles
European Conference on Antennas and Propagation
p. 3675-3678
Presentation's date: 2013-04-08
Presentation of work at congresses

A simple and precise technique to measure the sudden Extreme Ultraviolet (EUV) radiation increase of the Sun, during mid and strong flares, has been formulated and demonstrated for the most active part of the last Solar Cycle. On the one hand, it is based on the short time scale of these events, which allows the validity of a simple global overionization model. And on the other hand on the prompt ionospheric response to the EUV ionization, which signature (in terms of the Global Navigation Satellite Systems -GNSSSolar Flare Activity Indicator, GSFLAI) is accurately measured in real-time from the existing global networks of dual-frequency GNSS receivers, and with a time resolution higher that those of dedicated space probes. Moreover the sensitivity of this approach enables the detection of not only extreme X-class flares, but also the detection of variations of one order of magnitude lower or even smaller (such as for M-class flares): 100% successful detection for all the X-class solar flares during 2000-2006 with registered location outside of the solar limb (i.e. detection of 94% of all of X-class solar-flares) and about 65% for M-class ones, obtained with the associated SISTED detector. In summary, its full availability, continuity, high precision and integrity for mid and high solar flare effects on Ionosphere, can make GSFLAI an useful indicator of potential Space Weather activity for many users in radio propagation. These results, which have been recently published by the authors, are extended in this work up to one complete solar cycle, and using a lower sampling rate (30 seconds), demonstrating the better behaviour of this indirect solar EUV variability proxy (GSFLAI30), when comparisons are made with direct measurements from space probes, providing readings which can be affected by the late enhancement of particles.

Gonzalez Casado, Guillermo; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Sanz Subirana, Jaime
Journal of geophysical research
Vol. 118, num. 11, p. 7348-7359
DOI: 10.1002/2013JA019099
Date of publication: 2013
Journal article

A simple model for the topside ionosphere region is introduced and applied to fit radio-occultation retrieved electron density profiles for altitudes above the F2-peak. The model considers two isothermal components representing the population of the O+ (ionosphere component) and the H+ (protonosphere component) ions. The purpose of the model is to achieve an accurate fit of the observed profiles in the topside ionosphere region while, at the same time, allowing a direct and simple derivation of two important ionospheric parameters, namely, the O+ vertical scale height and the upper transition height. Covering a time period of one year, the fits with the two-component model function are compared with those achieved with one-component functions commonly used in the literature and it is shown that the former provides significantly better fits than the later, with more than a factor of two improvement. The model predictions concerning: the correlation between the O+ vertical scale height and the upper transition height, the altitude dependence of the vertical scale height of the electron density, and the quantitative contribution of the protonosphere to the total electron content are examined and shown to be consistent with the observations and with previous studies. It is concluded that the model provides a realistic description of the vertical distribution of the two main ion constituents of the topside ionosphere.

• Contributions to ionospheric determination with Global Positioning System: solar flare detection and prediction of global maps of Total Electron Content.

Garcia Rigo, Alberto
Universitat Politècnica de Catalunya
Theses

Two research studies have been addressed in this thesis. Both of them are of actual scientific interest and are based on processing GNSS data. The first part of this thesis is devoted to GNSS detection and monitoring of solar flares. The second one is devoted to GNSS prediction of ionospheric Total Electron Content. Regarding the first study, a new solar flare detector called SISTED has been designed and implemented. Its goal is to provide a simple and efficient way of detecting the most number of powerful X-class solar flares in real time operation. In addition, it can send early warning messages to prevent the harmful consequences of the increase of ejected particles from the Sun that may reach the Earth after a solar flare, especially in case of a Coronal Mass Ejection. The main benefit of SISTED regarding other detection techniques is that it does not require data from external providers out of the GNSS community. In addition, it can run in real-time operation and could provide value added data to GNSS users. The results show that SISTED was able to detect up to the 95% of the X-class flares reported by GOES for more than a half solar cycle. Regarding the second study, a new approach to predict Global Ionospheric vertical TEC Maps has been designed and implemented in the context of the IGS Ionosphere Working Group. The motivation to develop a UPC Predicted product was the interest of ESA's SMOS mission. A recent application using UPC Predicted products is the generation of real-time global VTEC maps as background model. In addition, the predicted VTEC maps are used to generate the combined IGS Predicted products. The results obtained in this thesis show that the model performs well when the results are compared with those obtained by the other IGS analysis centers. In addition, applying the prediction model leads to better results than the use of time-invariant ionosphere for two days ahead. In relation with this research, 4 publications in international journals indexed in JCR/ISI have been generated (and another one is under review process), and 7 presentations have been authored in international meetings, among the new UPC predicted product contributing to IGS, and the contribution to two competitive projects funded by the European Space Agency (AGIM and MONITOR).

• GNSS measurement of EUV photons flux rate during strong and mid solar flares

Hernandez Pajares, Manuel; Garcia Rigo, Alberto; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Monte Moreno, Enrique; Aragon Angel, Maria Angeles
Space weather: the international journal of research and applications
Vol. 10, num. 12, p. 1-16
DOI: 10.1029/2012SW000826
Date of publication: 2012-12-12
Journal article

• IONO-DeCo: executive summary of Ionospheric Delay Corrections in GNSS Signals for High Precision Applications

Aragon Angel, Maria Angeles; Hernandez Pajares, Manuel; Defraigne, Pascale
Date: 2012-12-09
Report

• Fast precise point positioning performance based on international GNSS real-time service data

Rovira Garcia, Adrià; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel
ESA Workshop on Satellite Navigation Technologies
DOI: 10.1109/NAVITEC.2012.6423100
Presentation's date: 2012-12-05
Presentation of work at congresses

• Monitoring, tracking and forecasting ionospheric perturbations using GNSS techniques

Jakowski, N; Béniguel, Yannick; De Franceschi,, Giorgiana; Hernandez Pajares, Manuel; Jacobsen, Knut Stanley; Stanislawska, Iwona; Tomasik, Lukasz; Warnant, René; Wautelet, Gilles
Journal of Space Weather and Space Climate
Vol. 2, num. A22, p. 1-14
DOI: 10.1051/swsc/2012022
Date of publication: 2012-12-01
Journal article

The paper reviews the current state of GNSS-based detection, monitoring and forecasting of ionospheric perturbations in Europe in relation to the COST action ES0803 ‘‘Developing Space Weather Products and Services in Europe’’. Space weather research and related ionospheric studies require broad international collaboration in sharing databases, developing analysis software and models and providing services. Reviewed is the European GNSS data basis including ionospheric services providing derived data products such as the Total Electron Content (TEC) and radio scintillation indices. Fundamental ionospheric perturbation phenomena covering quite different scales in time and space are discussed in the light of recent achievements in GNSS-based ionospheric monitoring. Thus, large-scale perturbation processes characterized by moving ionization fronts, wave-like travelling ionospheric disturbances and finally small-scale irregularities causing radio scintillations are considered. Whereas ground and space-based GNSS monitoring techniques are well developed, forecasting of ionospheric perturbations needs much more work to become attractive for users who might be interested in condensed information on the perturbation degree of the ionosphere by robust indices. Finally, we have briefly presented a few samples illustrating the space weather impact on GNSS applications thus encouraging the scientific community to enhance space weather research in upcoming years.

• Ionospheric effects on GNSS performance

Béniguel, Yannick; Angling, M; Banfi, E.; Bourga, C.; Cueto, M.; Fleury, R.; Garcia Rigo, Alberto; Hamel, P.; Hartmann, R.; Hernandez Pajares, Manuel; Jakowski, Norbert; Kauristie, Kirsti; Orús Pérez, Raul; Prieto Cerdeira, Roberto; Valette, Jean Jaques; Van de Kamp, M.
IEEE Computer Society
p. 1-8
DOI: 10.1109/NAVITEC.2012.6423122
Presentation's date: 2012-12
Presentation of work at congresses

This paper presents the features of the MONITOR project. This project initiated by ESA/ESTEC aims to increase the knowledge of the ionospheric effects and its impact on GNSS systems during active periods of solar activity. It includes the deployment of a set of GNSS-based ionospheric monitoring receivers worldwide distributed, the development of specific analysis software tools some of them integrated on a common platform, others distributed providing products routinely and a measurement campaign which will last beyond the peak of the current solar cycle

• Method, apparatus and system for determining a position of an object having a Global Navigation Satellite System receiver by processing undifferenced data like carrier phase measuurements and external products like ionosphere data

Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Samson, Jaron; Tossaint, Michel Mathias Maria
Date of request: 2012-10-04
Invention patent

• Enhanced precise point positioning for GNSS users

Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Sanz Subirana, Jaime; Ramos Bosch, Pedro; Aragon Angel, Maria Angeles; Orús Pérez, Raul; Ochieng, Washington; Feng, Shaojun; Jofre, Martí; Coutinho, Pedro; Samson, Jaron; Tossaint, Michel Mathias Maria
IEEE transactions on geoscience and remote sensing
Vol. 50, num. 10, p. 4213-4222
DOI: 10.1109/TGRS.2012.2189888
Date of publication: 2012-09-21
Journal article

This paper summarizes the main results obtained during the development of an Enhanced Precise Point Positioning (EPPP) Global Navigation Satellite Systems multifrequency user algorithm. The main innovations include the application of precise ionospheric corrections to facilitate the resolution of undifferenced carrier phase ambiguities, ambiguity validation, and integrity monitoring. The performance of the EPPP algorithm in terms of accuracy, convergence time, and integrity is demonstrated with actual GPS and simulated Galileo data. This can be achieved with very limited bandwidth requirements for EPPP users (less than 300 b/s for dual-frequency GPS data).

• TN1.2: historical analysis of ionospheric key performance indicators

Hernandez Pajares, Manuel
Date: 2012-09-19
Report

• IONO-DeCo: TN2- Definition of improved algorithms in high order ionospheric corrections

Aragon Angel, Maria Angeles; Hernandez Pajares, Manuel; Defraigne, Pascale; Bergeot, Nicolas
Date: 2012-07-23
Report

• IONO-DeCo: TN5 - validation and performance analysis of Ionospheric High Order modeling

Defraigne, Pascale; Hernandez Pajares, Manuel; Aragon Angel, Maria Angeles
Date: 2012-07-04
Report

• Assimilating the IRI-Plas model to the ionospheric hourly maps of GPS-TEC to produce the artificial foF2 and hmF2 global maps

Gulyaeva, Tamara L.; Arikan, Feza; Hernandez Pajares, Manuel; Stanislawska, Iwona; Sezen, Umut
Scientific Assembly of the Committee on Space Research
p. 1-2
Presentation's date: 2012-07
Presentation of work at congresses

• IONO-DeCo: final report - validation and performance analysis of higher order ionospheric modeling

Aragon Angel, Maria Angeles; Hernandez Pajares, Manuel; Defraigne, Pascale
Date: 2012-06-12
Report

• The International GNSS Real-Time Service

Caissy, Mark; Agrotis, Lukas; Weber, Georg; Hernandez Pajares, Manuel; Hugentobler, Urs
Gps world
Date of publication: 2012-06-01
Journal article

• IONO-DeCo: TN3 - Ionospheric delay corrections in GNSS signals for high precision applications

Aragon Angel, Maria Angeles; Hernandez Pajares, Manuel; Defraigne, Pascale; Bergeot, Nicolas
Date: 2012-06-01
Report

• IONO-DeCO: TN4 - Ionospheric High Order Test data campaign

Aragon Angel, Maria Angeles; Hernandez Pajares, Manuel
Date: 2012-06-01
Report

• Wide Area RTK: a satellite navigation system based on precise real-time ionospheric modelling

Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel; Samson, Jaron; Tossaint, Michel Mathias Maria; Aragon Angel, Maria Angeles; Salazar Hernández, Dagoberto José
Vol. 47, p. 1-14
DOI: 10.1029/2011RS004880
Date of publication: 2012-04-19
Journal article

The Wide Area Real Time Kinematic (WARTK) is an augmentation system concept for multi-frequency users based on precise real-time ionospheric modeling. It is able to provide a high accuracy and integrity GNSS positioning service over continental areas using the infrastructure of a network of permanent ground monitor stations, such as the European Geostationary Navigation Overlay Service (EGNOS) network of Ranging and Integrity Monitoring Stations (RIMS) in Europe. In this way, it allows an additional benefit to be obtained from these reference stations, that is, the network has the potential to support two independent systems: a satellite-based augmentation system, such as EGNOS, and a high-precision positioning service, based on WARTK. Indeed, thanks to the accuracy of the ionospheric corrections provided, WARTK users have available in real-time an extra constraint per satellite between the carrier phase ambiguities, which helps solve them quickly. Once such ambiguities have been solved, the GNSS user obtains navigation accurate to within 20 cm at the 95th percentile (about 10 cm RMS). Moreover, this precise positioning is achieved in a few minutes (with two frequency signals) or in a single epoch, after initial convergence of the tropospheric delay (with three frequency signals), even up to hundreds of kilometers away from the nearest reference station. While previous WARTK research has been devoted to implementing the concept and assessing its feasibility, considering in particular the accuracy achievable, the work reported in this paper focused on consolidating the results by analyzing a large and representative data set, and on deeper analysis of the integrity issue. It was carried out in the context of the Multi-constellation Regional System (MRS) project, within the European Space Agency GNSS Evolution Programme, with the aim of designing a high accuracy service for GPS and/or Galileo. Three months of actual data, from more than 25 permanent GPS stations in Europe, have been processed (some of them as a roving user), for high-, mid- and low-solar cycle conditions (in 2002, 2004 and 2006 respectively). In addition, several ionospheric storms occurred during the selected periods, with Dst values reaching up to −150 nT. Results based on these data show that user domain integrity was maintained for baselines of up to 400 km. At the 95th percentile, the daily horizontal and vertical position errors were 20 and 30 cm, respectively, and the corresponding protection levels were about 1 and 2 m. The convergence time was around 5 minutes with actual GPS constellation data. The benefits of using a multi-constellation system were also studied, with simulated GPS and three-frequency Galileo data, showing that it is possible to reduce the convergence time to a few seconds.

• Fast Precise Point Positioning based on real-time ionospheric modelling

Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Sanz Subirana, Jaime; Samson, Jaron; Tossaint, Michel Mathias Maria
PPP-RTK & Open Standards Symposium
Presentation's date: 2012-03-12
Presentation of work at congresses

Summary of main results of new technique Fast Precise Point Positioning developed in the framework of the ¿Enhanced Precise Point Positioning (EPPP) GNSS multifrequency user algorithm¿ ESA funded project. -The precise ionospheric corrections facilitate the resolution of undifferenced carrier phase ambiguities, ambiguity validation and integrity monitoring. -The FPPP performance is shown in terms of accuracy, convergence time and integrity, with actual GPS and simulated Galileo data. -Very limited bandwidth requirements for future EPPP users (less than 300 bps for dual-frequency GPS data).

Summary of main results of new technique Fast Precise Point Positioning developed in the framework of the “Enhanced Precise Point Positioning (EPPP) GNSS multifrequency user algorithm” ESA funded project. -The precise ionospheric corrections facilitate the resolution of undifferenced carrier phase ambiguities, ambiguity validation and integrity monitoring. -The FPPP performance is shown in terms of accuracy, convergence time and integrity, with actual GPS and simulated Galileo data. -Very limited bandwidth requirements for future EPPP users (less than 300 bps for dual-frequency GPS data).

• Fast Precise Point Positioning for decimeter-error-level navigation for multi and single-frequency users of Global Navigation Satellite Systems

Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Sanz Subirana, Jaime; Samson, Jaron; Tossaint, Michel Mathias Maria
European Calibration and Orientation Workshop
p. 1-10
Presentation's date: 2012-02
Presentation of work at congresses

This manuscript summarizes the new algorithm of Fast Precise Point Positioning (FPPP) the developed during the projects "Enhanced PPP GNSS multifrequency user algorithm" and ¿Precise Real Time Orbit Determination and Time synchronisation¿, both funded by the European Space Agency (ESA). The main innovations achieved during the overall project comprise the application of precise ionospheric corrections to facilitate the fast resolution of undifferenced carrier phase ambiguities, ambiguity validation and integrity monitoring for both multi- and single-frequency users. Among the integrity, detailed in previous works, the performance of the FPPP algorithm in terms of improved accuracy and convergence time is demonstrated with actual GPS and simulated Galileo data. The 10-centimeters error level real-time kinematic positioning can be achieved in few minutes for dual-and single-frequency users, almost instantaneous for three-frequency users (or once the tropospheric delay is well estimated in few minutes in cold start), and with very limited bandwidth requirements for the FPPP users (less than 300 bps for dual-frequency GPS)

This manuscript summarizes the new algorithm of Fast Precise Point Positioning (FPPP) the developed during the projects "Enhanced PPP GNSS multifrequency user algorithm" nd “Precise Real Time Orbit Determination and Time synchronisation”, both funded by the European Space Agency (ESA). The main innovations achieved during the overall project comprise the application of precise ionospheric corrections to facilitate the fast resolution of undifferenced carrier phase ambiguities, ambiguity validation and integrity monitoring for both multi- and single-frequency users. Among the integrity, detailed in previous works, the performance of the FPPP algorithm in terms of improved accuracy and convergence time is demonstrated with actual GPS and simulated Galileo data. The 10-centimeters error level real-time kinematic positioning can be achieved in few minutes for dual-and single-frequency users, almost instantaneous for three-frequency users (or once the tropospheric delay is well estimated in few minutes in cold start), and with very limited bandwidth requirements for the FPPP users (less than 300 bps for dual-frequency GPS).

• IONO-DECO monthly progress report no 6

Aragon Angel, Maria Angeles; Hernandez Pajares, Manuel
Date: 2012-01-02
Report

• Propagation of medium scale traveling ionospheric disturbances at different latitudes and solar cycle conditions

Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles
Vol. 47, num. 4
DOI: 10.1029/2011RS004951
Date of publication: 2012
Journal article

• Integrity monitoring for carrier phase ambiguities

Feng, Shaojun; Ochieng, Washington; Samson, Jaron; Tossaint, Michel Mathias Maria; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles; Ramos Bosch, Pedro; Jofre, Martí
Vol. 65, num. 1, p. 41-58
DOI: 10.1017/S037346331100052X
Date of publication: 2012-01
Journal article

The determination of the correct integer number of carrier cycles (integer ambiguity) is the key to high accuracy positioning with carrier phase measurements from Global Navigation Satellite Systems (GNSS). There are a number of current methods for resolving ambiguities including the Least-squares AMBiguity Decorrelation Adjustment (LAMBDA) method, which is a combination of least-squares and a transformation to reduce the search space. The current techniques to determine the level of confidence (integrity) of the resolved ambiguities (i.e. ambiguity validation), usually involve the construction of test statistics, characterisation of their distribution and definition of thresholds. Example tests applied include ratio, F-distribution, t-distribution and Chi-square distribution. However, the assumptions that underpin these tests have weaknesses. These include the application of a fixed threshold for all scenarios, and therefore, not always able to provide an acceptable integrity level in the computed ambiguities. A relatively recent technique referred to as Integer Aperture (IA) based on the ratio test with a large number of simulated samples of float ambiguities requires significant computational resources. This precludes the application of IA in real time. This paper proposes and demonstrates the power of an integrity monitoring technique that is applied at the ambiguity resolution and positioning stages. The technique has the important benefit of facilitating early detection of any potential threat to the position solution, originating in the ambiguity space, while at the same time giving overall protection in the position domain based on the required navigation performance. The proposed method uses the conventional test statistic for ratio testing together with a doubly non-central F distribution to compute the level of confidence (integrity) of the ambiguities. Specifically, this is determined as a function of geometry and the ambiguity residuals from least squares based ambiguity resolution algorithms including LAMBDA. A numerical method is implemented to compute the level of confidence in real time. The results for Precise Point Positioning (PPP) with simulated and real data demonstrate the power and efficiency of the proposed method in monitoring both the integrity of the ambiguity computation and position solution processes. Furthermore, due to the fact that the method only requires information from least squares based ambiguity resolution algorithms, it is easily transferable to conventional Real Time Kinematic (RTK) positioning.

• Plasmaspheric Electron Content contribution inferred from ground and radio occultation derived Total Electron Content

Aragon Angel, Maria Angeles; Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Altadill, D.
IEEE International Conference on Communications
p. 257-262
DOI: 10.1109/CCE.2012.6315908
Presentation's date: 2012
Presentation of work at congresses