Beacon Satellite Symposium: Session 5B - June 30th 2016: Radio occultation techniques and measurements

During the Beacon Satellite Symposium, held in Trieste, Italy, between June 26 and July 1 2016, the JRC chaired the session 5B: Radio Occultation Techniques and Measurements. The corresponding abstract of the session is provided as follows: Since the mid-1960s, the GNSS based radio occultation technique has been used to study the structure and properties of the atmospheres of not only Earth but also other planets, such as Venus, Mars, some other outer planets, and many of their moons. By measuring the phase delay of radio waves from GNSS satellites as they are occulted by the Earth’s atmosphere, the vertical density profiles of the bending angles of radio wave trajectories can be estimated using measurements onboard LEO satellites. The success of the GPS/MET mission in 1995 inspired a number of follow-on missions that include radio occultation experiment, including the CHAMP, GRACE, SAC-C, COSMIC, Metop-A/B, C/NOFS, and upcoming COSMIC-2 satellites. The combined profiles from these different LEO satellites provide excellent opportunities to explore the dynamics and structure of the ionosphere, especially in the regions that have been devoid of ground-based instruments, allowing for investigation of the longitudinal variability of the ionospheric density structure. This session seeks contributions that advance the application of RO technique for space weather studies. In addition, we welcome presentations exploring innovative methodologies that address the current problem on RO inversion technique at the equatorial region where ionospheric irregularity, such as sporadic E and spread F, present and degrade the linear combination technique that affect the quality of density profile extracted in the region. The session was organized among Endawoke Yizengaw (Institute for Scientific Research, Boston College), Jann-Yenq Liu (National Space Organization –NSPO- Chief Scientist), and Angela Aragon-Angel (Joint Research Centre). The session consisted of both oral and poster presentation parts.Preprin

Software prototype for the Galileo ionospheric correction model: progress report

This particular report includes a description of the JRC NeQuick source code (JRC NeQuickG) and comments on the challenges faced to implement it. Emphasis on the System Architecture is put in order to help any potential follow up of this project in the near future.The document describing the particular ionospheric model developed for the Galileo satellite navigation system has been officially released [1]. Its publication allows GNSS receiver manufacturers to start the implementation of the specific algorithm targeted for their Galileo related products in order to be compliant with the Galileo system. Some of such implementations have already been supported by Unit G05 (now E.2) in the framework of an on-going support activity under the EU GNSS Programmes with DG GROW and GSA, responding to inquiries from the receiver manufacturers Broadcom and Javad. The only way to support the development of the new Galileo ionospheric correction in an efficient and timely manner is to have our own developed model as an official Galileo Programme reference (i.e. the European Commission) product to assess and help correcting external implementations, which will definitely have a direct impact on industry and, in return, society. Once the JRC NeQuickG product is available, further developments have been already foreseen: optimize the algorithm and tailor it to the needs of the various users, notably in terms of accuracy. This particular report includes a description of the JRC NeQuick source code (JRC NeQuickG) and comments on the challenges faced to implement it. Emphasis on the System Architecture is put in order to help any potential follow up of this project in the near future.Preprin

Modelizando el calculo de varias variablEEES en el aula

La implantaci on de la modelizaci on matem atica en el ambito del Espacio Europeo de Educaci on Superior (EEES) necesita de una revisi on y adaptaci on de los contenidos y estrategias para abordar las asignaturas, en particular, aquellas m as te oricas y abstractas, para fomentar su car acter interdisciplinario. Se presenta una nueva propuesta metodol ogica para la asignatura de An alisis Vectorial (c alculo multivariable) ofertada durante los ultimos a~nos por l'Escola T ecnica Superior d'Enginyeria de Telecomunicacions de Barcelona (ETSETB) de la Universitat Polit ecnica de Catalunya (UPC). Es una de las asignaturas de la fase selectiva de dicha titulaci on, con 4.5 cr editos de teor a y 3 de pr acticas (repartidos entre problemas y laboratorios). The implantation of mathematical modelling in the framework of the European Higher Education Area (EHEA) needs a revision and adaptation of content and strategies to address the curricula, in particular those subjects which are more theoretical and abstract, to encourage their interdisciplinary character. We present a new proposal of methodology for the subject of Vector Analysis (multivariable calculus) o ered last years by the Escola T ecnica Superior d'Enginyeria de Telecommunicaci o de Barcelona (ETSETB) of the Universitat Polit ecnica de Catalunya (UPC). It is a subject within the selective phase of the undergraduate program with 4.5 credits for theory and 3 for practice (divided between problems and laboratories).Peer ReviewedPostprint (published version

Modelizando el cálculo de varias variablEEES en el aula

La implantación de la modelización matemática en el ámbito del Espacio Europeo de Educación Superior (EEES) necesita de una revisión y adaptación de los contenidos y estrategias para abordar las asignaturas, en particular, aquellas más teóricas y abstractas para fomentar su carácter interdisciplinario. Se presenta una nueva propuesta metodológica para la asignatura de Análisis Vectorial (cálculo multivariable) ofertada durante los últimos años por l’Escola Tècnica Superior d’Enginyeria de Telecomunicacions de Barcelona (ETSETB) de la Universitat Politècnica de Catalunya (UPC). Es una de las asignaturas de la fase selectiva de dicha titulación, con 4.5 créditos de teoría y 3 de prácticas (repartidos entre problemas y laboratorios).Postprint (published version

The selection of basic functions for a time-varying model of unmodeled errors in medium and long GNSS baselines

Unmodeled errors play a critical role in improving the positioning accuracy of Global Navigation Satellite Systems. Few studies have addressed unmodeled errors in medium and long baselines using their time correlation, which is highly beneficial for achieving a precise and real-time solution. However, before tackling unmodeled errors, it is first necessary to determine reasonable basic functions to fit such unmodeled errors. Therefore, we study the selection of basic functions for time-varying unmodeled errors in two positioning modes: estimating atmospheric delays and using an IF combination. We choose three basic functions: polynomials, sinusoidal functions, and combinatorial functions. Fitting experiments and positioning experiments are conducted using the unmodeled error data provided by four baselines ranging from 30 to 220 km. The Root Mean Square Errors fitted by the second order are approximately 2 mm. The corresponding residuals generally converge to 3 mm in about 30 s. After correcting the observations using the fitted unmodeled errors of the second-order polynomial, the positioning results show improvements of about 40% to 80% in all directions. We conclude that the second-order polynomial is the optimal basic function in all two positioning modes.This study was supported by the National Natural Science Foundation of China (Project No. 41974030; 41674035). Jiafu Wang acknowledges financial support from the China Scholarship Council (Grant No. 202206090184). Adria Rovira acknowledges financial support from the Spanish Ministry of Science and Innovation projects: CNS2022-135383 and PID2022-138485OB-I00.Peer ReviewedPostprint (published version

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

The FORMOSAT-3/COSMIC satellite constellation has become an important source of remote sensing data globally distributed for the sounding of the atmosphere of the Earth and, in particular, the ionosphere. In this study, electron density profiles derived using the Improved Abel transform inversion in Radio Occultation (RO) scenarios are used as input data to derive some features regarding the topside and outside ionospheric contribution, hence, the plasmasphere in great extend, by means of the analysis of the integral values of the shape functions corresponding to each density profile. The novelty presented in this paper, with respect to previous works, is the use of experimental data from the FORMOSAT-3/COSMIC RO-derived electron densities to infer global characterizations and distribution of the Total Electron Content (TEC) into its main components: ionospheric TEC and plasmaspheric TEC, both contributing to TEC. The results show agreement with earlier modeled and observational data from previous local studies of the plasmaspheric contribution. The main conclusion of this research is that the plasmasphere contributes significantly to TEC and the ratio between plasmaspheric TEC and TEC has been climatologically analyzed for the whole year 2007 confirming that the major relative impact of the plasmasphere is during night time. The added value of this study is that the results obtained are globally distributed and can help to infer a proxy for the plasmaspheric contribution at any location over the globe thanks to the FORMOSAT-3/COSMIC coverage.Peer ReviewedPostprint (published version

Impact of higher order ionospheric delay on precise GNSS computation

Peer ReviewedPostprint (published version

Preliminary NeQuick assessment for future single frequency users of GALILEO

The NeQuick model is the ionospheric mo del that will be used by the GALILEO single frequency user to compute ionospheric corrections. In this framework, the aim of this study is to show a preliminary assessment of the performance of the NeQuick model using as metrics an independent source of TEC (Total Electron Content) such as altimetric satellites (in this case, TOPEX/Poseidon) that provide direct measurements of TEC.Peer ReviewedPostprint (published version

The User Domain Integrity Assessment Technique

This paper presents a study performed for the detailed analysis of user domain and pseudorange integrity on Satellite Based Augmentation Systems. Experimental data of EGNOS pre-operational service was used for some specific tests, aiming at identifying for instance the good reaction of the EGNOS check-set subsystem and the way pseudorange errors are translated into the user domain. From this analysis, a new technique for User Domain Integrity Assessment (UDIA) was developed. With the UDIA technique, the integrity is checked for all possible geometries from 4 to all satellites in view from a network of stations. When no MI is found (from a wide and sufficiently dense stations network), it can be assured that the system is safe, and it becomes the best experimental guarantee at the User Domain Level. If a NMI/MI appears from any geometry of satellites from the stations in the network, thence a search algorithm is applied to identify the satellite, or combinations of satellites, responsible of such NMI/MIs (i.e., their exclusion leads to the disappearance of the NMI/MIs). After identifying such satellites, the reaction of the EGNOS Check Set (CS) is evaluated by checking if they were set as DU or NM within a predefined time interval after the NMI/MI is detected.Peer Reviewe