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277 results on '"Hoque, Mainul"'

16. Evaluation of ionospheric models for Central and South Americas

Author

Klipp, Telmo dos Santos, Petry, Adriano, de Souza, Jonas Rodrigues, Falcão, Gabriel Sandim, de Campos Velho, Haroldo Fraga, de Paula, Eurico Rodrigues, Antreich, Felix, Hoque, Mainul, Kriegel, Martin, Berdermann, Jens, Jakowski, Norbert, Fernandez-Gomez, Isabel, Borries, Claudia, Sato, Hiroatsu, and Wilken, Volker

Published
2019
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20. Climatology and modeling of ionospheric irregularities over Greenland based on empirical orthogonal function method

Author

Jin Yaqi, Clausen Lasse B.N., Miloch Wojciech J., Høeg Per, Jarmołowski Wojciech, Wielgosz Paweł, Paziewski Jacek, Milanowska Beata, Hoque Mainul, Berdermann Jens, Lyu Haixia, Hernández-Pajares Manuel, and García-Rigo Alberto

Subjects
ionospheric irregularities, eof, modeling, space weather, roti, Meteorology. Climatology, QC851-999
Abstract

This paper addresses the long-term climatology (over two solar cycles) of total electron content (TEC) irregularities from a polar cap station (Thule) using the rate of change of the TEC index (ROTI). The climatology reveals variabilities over different time scales, i.e., solar cycle, seasonal, and diurnal variations. These variations in different time scales can be explained by different drivers/contributors. The solar activity (represented by the solar radiation index F10.7P) dominates the longest time scale variations. The seasonal variations are controlled by the interplay of the energy input into the polar cap ionosphere and the solar illumination that damps the amplitude of ionospheric irregularities. The diurnal variations (with respect to local time) are controlled by the relative location of the station with respect to the auroral oval. We further decompose the climatology of ionospheric irregularities using the empirical orthogonal function (EOF) method. The first four EOFs could reflect the majority (99.49%) of the total data variability. A climatological model of ionospheric irregularities is developed by fitting the EOF coefficients using three geophysical proxies (namely, F10.7P, Bt, and Dst). The data-model comparison shows satisfactory results with a high Pearson correlation coefficient and adequate errors. Additionally, we modeled the historical ROTI during the modern grand maximum dating back to 1965 and made the prediction during solar cycle 25. In such a way, we can directly compare the climatic variations of the ROTI activity across six solar cycles.

Published
2022
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25. Activities of the JWG 4.3.4 - Validation of VTEC models for high-precision and high resolution applications

Author

Krypiak-Gregorczyk, Anna, Komjathy, Attila, Wielgosz, Pawel, Milanowska, Beata, Jarmołowski, Wojciech, Goss, Andreas, Erdogan, Eren, Schmidt, Michael, Liu, Qi, Lyu, Haixia, Hernández-Pajares, Manuel, Hoque, Mainul, Shengfeng, Gu, Ghoddousi-Fard, Reza, and Orus-Perez, Raul

Abstract

The global and regional ionospheric maps are often used for a wide range of applications in geosciences, in particular to support precise positioning, but also for geophysical and atmospheric studies. There are currently many analysis centers and research groups providing operational and test VTEC maps. However, IGS ACs and other groups use different mathematical models and estimation techniques resulting different resolutions, accuracies and time delays of their products. Therefore, there is a need to compare and validate existing VTEC models.In this presentation, we present the overview talk about the work within the last 4 years of the IAG Joint Working Group (JWG 4.3.4) on validation of VTEC models for high-precision and high resolution applications. Among others, we evaluated (1) the accuracy and consistency of the IAAC GIMs during high and low solar activity periods of the 24th solar cycle, (2) the accuracy the two most popular ionospheric mapping functions - SLM and MSLM, (3) deterministic and stochastic approaches to VTEC modelling, (4) GIMs performance in single point and precise point positioning GNSS applications, (5) the accuracy and consistency of GNSS-derived VTEC maps and empirical models, (6) GIMs performance using external data (JASON) and GNSS, (7) the accuracy of new global ionosphere models., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

31. Assessment of GRAS Ionospheric Measurements for Ionospheric Model Assimilation

Author

European Organisation for the Exploitation of Meteorological Satellites, Hoque, Mainul M., Prol, Fabricio S., Hernández-Pajares, Manuel, Notarpietro, Riccardo, Yuan, Liangliang, Olivares-Pulido, Germán, Graffigna, Victoria, Engeln, A. von, Marquardt, Christian, European Organisation for the Exploitation of Meteorological Satellites, Hoque, Mainul M., Prol, Fabricio S., Hernández-Pajares, Manuel, Notarpietro, Riccardo, Yuan, Liangliang, Olivares-Pulido, Germán, Graffigna, Victoria, Engeln, A. von, and Marquardt, Christian

Abstract

We conducted a study to assess the GNSS (Global Navigation Satellite System) Receiver for Atmospheric Sounding (GRAS) ionospheric data quality by processing Radio Occultation (RO) observations of ionospheric products. The main objective of the study is to validate ionospheric data generated at EUMETSAT, such as ionospheric bending angle profiles, amplitude and phase scintillations, topside Total Electron Content (TEC) from MetOp-A GRAS instrument as well as generating and validating new ionospheric products derived from GRAS RO observations such as the TEC, rate of TEC and vertical electron density profiles. The assessment is conducted by comparing and evaluating the systematic differences between similar products from other Low Earth Orbit (LEO) satellite missions or from ground-based ionospheric measurements. The study confirms that the GNSS topside and RO observations recorded by the GRAS instrument onboard MetOp satellites are of good quality and are a valuable source of data for ionospheric research.

Published
2023

32. Real-Time Tomographic Inversion of Truncated Ionospheric GNSS Radio Occultations

Author

Olivares-Pulido, Germán, Hernández-Pajares, Manuel, Monte-Moreno, Enric, Lyu, Haixia, Graffigna, Victoria, Cardellach, Estel, Hoque, Mainul M., Prol, Fabricio S., Notarpietro, Riccardo, García-Fernández, Miquel, Olivares-Pulido, Germán, Hernández-Pajares, Manuel, Monte-Moreno, Enric, Lyu, Haixia, Graffigna, Victoria, Cardellach, Estel, Hoque, Mainul M., Prol, Fabricio S., Notarpietro, Riccardo, and García-Fernández, Miquel

Abstract

This paper presents a new way of combining Abel inversion and the Chapman model with a linearly increasing scale height to retrieve ionospheric electron density vertical profiles from truncated-sounding radio-occultation data. A linear Vary–Chap model is used to cover the blind region due to data truncation, with parameters estimated by enumeration of the possible values in a grid centered around a set of parameters compatible with ionospheric physics. The resulting electron density is estimated with its corresponding error from the linear least-squares solution presenting the smaller post-fit residual on the input GNSS carrier-phase measurements. The results, tested on a set of representative GNSS RO measurements obtained by COSMIC/FORMOSAT-3, show that this method can retrieve EDVPs with a predominant absolute and relative error of 1010e−m−3 and 5%, respectively, and in less than 10 s per profile, which makes this method suitable for near real-time applications in upcoming missions such as EUMETSAT Polar System-Second Generation.

Published
2023

33. Topside ionospheric tomography exclusively based on LEO POD GPS carrier phases: Application to autonomous LEO DCB estimation

Author

European Commission, Hernández-Pajares, Manuel, Olivares-Pulido, Germán, Hoque, Mainul M., Prol, Fabricio S., Yuan, Liangliang, Notarpietro, Riccardo, Graffigna, Victoria, European Commission, Hernández-Pajares, Manuel, Olivares-Pulido, Germán, Hoque, Mainul M., Prol, Fabricio S., Yuan, Liangliang, Notarpietro, Riccardo, and Graffigna, Victoria

Abstract

This paper presents a novel technique to estimate DCBs from GPS transmitters and receivers on-board Low Earth Orbit (LEO) satellites. The technique consists of obtaining the DCBs as residuals from the difference between the ionospheric combination of the code and the associated ionospheric delay. The ionospheric delay is computed with TOMION, a background-model-free ionospheric tomographic technique based on dual-frequency GPS carrier phase data only, and solved with a Kalman filter. Thus, DCBs are also estimated epoch-wise from the LEO Precise Orbit Determination (POD) GPS receiver as a secondary product. The results for GPS satellite DCBs, obtained exclusively from the three MetOp LEO POD GPS receivers over four consecutive weeks, are in full agreement (i.e., at the level of a few tenths of ns) with those reported independently with other techniques from hundreds of ground-based receivers exclusively, by JPL and CODE analysis centers.

Published
2023

34. Topside ionospheric tomography exclusively based on LEO POD GPS carrier phases: application to autonomous LEO DCB estimation

Author

Universitat Politècnica de Catalunya. Departament de Matemàtiques, Universitat Politècnica de Catalunya. IonSAT - Grup de determinació Ionosfèrica i navegació per SAtèl·lit i sistemes Terrestres, Hernández Pajares, Manuel, Olivares Pulido, Germán, Hoque, Mainul, Prol, Fabricio dos Santos, Yuan, Liangliang, Notarpietro, Riccardo, Graffigna, Victoria, Universitat Politècnica de Catalunya. Departament de Matemàtiques, Universitat Politècnica de Catalunya. IonSAT - Grup de determinació Ionosfèrica i navegació per SAtèl·lit i sistemes Terrestres, Hernández Pajares, Manuel, Olivares Pulido, Germán, Hoque, Mainul, Prol, Fabricio dos Santos, Yuan, Liangliang, Notarpietro, Riccardo, and Graffigna, Victoria

Abstract

This paper presents a novel technique to estimate DCBs from GPS transmitters and receivers on-board Low Earth Orbit (LEO) satellites. The technique consists of obtaining the DCBs as residuals from the difference between the ionospheric combination of the code and the associated ionospheric delay. The ionospheric delay is computed with TOMION, a background-model-free ionospheric tomographic technique based on dual-frequency GPS carrier phase data only, and solved with a Kalman filter. Thus, DCBs are also estimated epoch-wise from the LEO Precise Orbit Determination (POD) GPS receiver as a secondary product. The results for GPS satellite DCBs, obtained exclusively from the three MetOp LEO POD GPS receivers over four consecutive weeks, are in full agreement (i.e., at the level of a few tenths of ns) with those reported independently with other techniques from hundreds of ground-based receivers exclusively, by JPL and CODE analysis centers., The work has been performed coinciding with the execution of the PITHIA-NRF H2020 project (H2020-INFRAIA-2018-2020101007599), Peer Reviewed, Postprint (published version)

Published
2023

35. Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from Space.

Author

Moreno, Mario, Semmling, Maximilian, Stienne, Georges, Hoque, Mainul, and Wickert, Jens

Subjects
GLOBAL Positioning System, REFLECTOMETRY, GRAZING, ELECTRON density, SOLAR activity, DOPPLER effect
Abstract

Coherent observations in GNSS reflectometry are prominent in regions with smooth reflecting surfaces and at grazing elevation angles. However, within these lower elevation ranges, GNSS signals traverse a more extensive atmospheric path, and increased ionospheric effects (e.g., delay biases) are expected. These biases can be mitigated by employing dual-frequency receivers or models tailored for single-frequency receivers. In preparation for the single-frequency GNSS-R ESA "PRETTY" mission, this study aims to characterize ionospheric effects under variable parameter conditions: elevation angles in the grazing range (5° to 30°), latitude-dependent regions (north, tropic, south) and diurnal changes (day and nighttime). The investigation employs simulations using orbit data from Spire Global Inc.'s Lemur-2 CubeSat constellation at the solar minimum (F10.7 index at 75) on March, 2021. Changes towards higher solar activity are accounted for with an additional scenario (F10.7 index at 180) on March, 2023. The electron density associated with each reflection event is determined using the Neustrelitz Electron Density Model (NEDM2020) and the NeQuick 2 model. The results from periods of low solar activity reveal fluctuations of up to approximately 300 TECUs in slant total electron content, 19 m in relative ionospheric delay for the GPS L1 frequency, 2 Hz in Doppler shifts, and variations in the peak electron density height ranging from 215 to 330 km. Sea surface height uncertainty associated with ionospheric model-based corrections in group delay altimetric inversion can reach a standard deviation at the meter level. [ABSTRACT FROM AUTHOR]

Published
2023
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45. 3D ionospheric imaging for space weather monitoring at low-latitudes

Author

Prol, Fabricio, Camargo, Paulo, Muella, Marcio, Hoque, Mainul, Hernández-Pajares, Manuel, Ana, Souza, Bhuiyan, Zahidul, and Kaasalainen, Sanna

Abstract

Three-dimensional (3D) ionospheric imaging at Low-Latitudes is challenging due to the high ionospheric variability and dynamics in the region. The region is characterized by the presence of the Equatorial Ionization Anomaly (EIA), plasma bubbles, layered structures, and strong vertical drifts upwards during the evening pre-reversal enhancement. Aiming to better understand the ionosphere at low latitudes, this study shows the latest developments conducted by the authors to map the region with 3D inversion algorithms based on Global Navigation Satellite Systems (GNSS), ionosondes, GNSS radio-occultation, and empirical models, such as the International Reference Ionosphere (IRI). We address the capabilities of the developed 3D imaging methods to disclose the main morphologies and dynamics of the ionospheric electron density in the region. Limitations are also discussed since data assimilation schemes are still ill-conditioned for a complete 3D reconstruction. Based on the experiments conducted by the authors, the main conclusions have outlined that better 3D representation of the ionosphere in the region of particular interest requires three main improvements: 1) denser GNSS networks on ground and space; 2) better representation by empirical models to be used as background to the inversion technique, mainly to better represent the plasmasphere, topside ionosphere, and during the pre-reversal enhancements; and 3) ionosphere sounding using GNSS or beacon like signals transmitted by Low Earth Orbit (LEO) satellites., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

46. A new plasmapause model based on IMAGE RPI and Van Allen probe data via automatic detection

Author

Banyś, Daniela, Feltens, Joachim, Jakowski, Norbert, and Hoque, Mainul

Abstract

The plasmapause, i.e. the outer boundary of the plasmasphere, is characterised by a sharp electron density gradient. The Neustrelitz ESOC PlasmaPause Model (NEPPM) is a newly developed model of the plasmapause location Lpp. The actual plasmapause positions are derived from the electron density measurements recorded onboard the IMAGE satellite between 2000 and 2005 and the Van Allen probes between 2012 and 2018. An automatic algorithm is developed for detecting plasmapause location along electron density versus altitude profile. The NEPPM model functions are fitted to the Lpp measurements in a least squares sense and model parameters are determined. In our NEPPM approach an ellipse is assumed to describe the principal plasmapause shape in the geomagnetic equatorial plane. This is aligned with the bulge that follows the level of solar activity. Embedded into a 3D approach, the NEPPM allows non-dipole B vectors, providing 3D positions on the plasmapause torus for given latitude, longitude, epoch and Dst. The underlying fitting procedures recreate the varying Lpp as a function of the Dst index and magnetic local time, which gives a better conformity than the GCPM (Global Core Plasma Model).We thank ESOC (ESA/ESOC/OPS-GN) for their active support in developing the model., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

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