scholarly journals A satellite-based method for modeling ionospheric slant TEC from GNSS observations: algorithm and validation

GPS Solutions ◽  
2021 ◽  
Vol 26 (1) ◽  
Author(s):  
Wen Li ◽  
Zishen Li ◽  
Ningbo Wang ◽  
Ang Liu ◽  
Kai Zhou ◽  
...  
Keyword(s):  
Mapping Function ◽  
Satellite System ◽  
Ionospheric Delay ◽  
Electron Content ◽  
Observation Data ◽  
Total Electron ◽  
Observation Network ◽  
Different Seasons ◽  
Global Navigation Satellite ◽  
Validation Tests

AbstractTotal Electron Content (TEC) modeling is critical for Global Navigation Satellite System (GNSS) users to mitigate ionospheric delay errors. The mapping function is usually used for Vertical TEC ionospheric correction models for slant and vertical TEC conversion. But the mapping function cannot characterize TEC variation in different azimuths between the user and satellites. The ionospheric modeling error resulting from the mapping function tends to be bigger in middle and low latitudes. Therefore, a new algorithm for ionospheric Slant TEC (STEC) modeling with Satellite-based Ionospheric Model (SIM) is proposed in this contribution. Validation tests are carried out with GNSS observation data from the Crustal Movement Observation Network of China during different solar activities and in different seasons. The performance of SIM is compared with that of several commonly-used Global Ionospheric Map (GIM) and Regional Ionospheric Map (RIM) products. The results show that the STEC bias and STD of SIM are within 1.0 TECU and about 2.0 TECU, respectively, and SIM can correct over 90% STEC RMS errors, outperforming the GIM and RIM products. Consequently, the SIM algorithm can be a new option for high-accuracy ionospheric delay correction in regional and local GNSS networks.

scholarly journals Investigation of Pre-Earthquake Ionospheric and Atmospheric Disturbances for Three Large Earthquakes in Mexico

Geosciences ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 16
Author(s):  
Christina Oikonomou ◽  
Haris Haralambous ◽  
Sergey Pulinets ◽  
Aakriti Khadka ◽  
Shukra R. Paudel ◽  
...  
Keyword(s):  
Chemical Potential ◽  
Atmospheric Model ◽  
Satellite System ◽  
Seismic Events ◽  
Electron Content ◽  
Total Electron ◽  
Atmospheric Disturbances ◽  
Global Ionospheric Maps ◽  
Global Navigation Satellite ◽  
Large Earthquakes

The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hours to a few days prior to the seismic events may be linked to the forthcoming events and most of them are nearly concurrent with atmospheric anomalies happening during the same day. This analysis also highlights that even in low-latitude areas it is possible to discern pre-earthquake ionospheric disturbances possibly linked with the imminent seismic events.

scholarly journals Characterization of multi-scale ionospheric irregularities using ground-based and space-based GNSS observations

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
YuXiang Peng ◽  
Wayne A Scales ◽  
Michael D Hartinger ◽  
Zhonghua Xu ◽  
Shane Coyle
Keyword(s):  
Formation Flying ◽  
Satellite System ◽  
Ionospheric Irregularities ◽  
Mission Design ◽  
Electron Content ◽  
Total Electron ◽  
Spatial And Temporal Scales ◽  
Multi Scale ◽  
Global Navigation Satellite ◽  
Gnss Observations

AbstractIonospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). However, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fully understood. This paper reviews Virginia Tech’s recent studies on multi-scale ionospheric irregularities using ground-based and space-based GNSS observations. First, the relevant background of ionospheric irregularities and their impact on GNSS signals is reviewed. Next, three topics of ground-based observations of ionospheric irregularities for which GNSS and other ground-based techniques are used simultaneously are reviewed. Both passive and active measurements in high-latitude regions are covered. Modelling and observations in mid-latitude regions are considered as well. Emphasis is placed on the increased capability of assessing the multi-scale nature of ionospheric irregularities using other traditional techniques (e.g., radar, magnetometer, high frequency receivers) as well as GNSS observations (e.g., Total-Electron-Content or TEC, scintillation). Besides ground-based observations, recent advances in GNSS space-based ionospheric measurements are briefly reviewed. Finally, a new space-based ionospheric observation technique using GNSS-based spacecraft formation flying and a differential TEC method is demonstrated using the newly developed Virginia Tech Formation Flying Testbed (VTFFTB). Based on multi-constellation multi-band GNSS, the VTFFTB has been developed into a hardware-in-the-loop simulation testbed with external high-fidelity global ionospheric model(s) for 3-satellite formation flying, which can potentially be used for new multi-scale ionospheric measurement mission design.

scholarly journals Investigation of GIM-TEC disturbances before M ≥ 6.0 inland earthquakes during 2003–2017

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Fuying Zhu ◽  
Yingchun Jiang
Keyword(s):  
Rapid Development ◽  
Science Research ◽  
Satellite System ◽  
Statistical Investigation ◽  
Electron Content ◽  
Total Electron ◽  
Spatial And Temporal Distributions ◽  
Before And After ◽  
Global Ionosphere Map ◽  
Global Navigation Satellite

Abstract With the rapid development of the Global Navigation Satellite System (GNSS) and its wide applications to atmospheric science research, the global ionosphere map (GIM) total electron content (TEC) data are extensively used as a potential tool to detect ionospheric disturbances related to seismic activity and they are frequently used to statistically study the relation between the ionosphere and earthquakes (EQs). Indeed, due to the distribution of ground based GPS receivers is very sparse or absent in large areas of ocean, the GIM-TEC data over oceans are results of interpolation between stations and extrapolation in both space and time, and therefore, they are not suitable for studying the marine EQs. In this paper, based on the GIM-TEC data, a statistical investigation of ionospheric TEC variations of 15 days before and after the 276 M ≥ 6.0 inland EQs is undertaken. After eliminating the interference of geomagnetic activities, the spatial and temporal distributions of the ionospheric TEC disturbances before and after the EQs are investigated and compared. There are no particularly distinct features in the time distribution of the ionospheric TEC disturbances before the inland EQs. However, there are some differences in the spatial distribution, and the biggest difference is precisely in the epicenter area. On the other hand, the occurrence rates of ionospheric TEC disturbances within 5 days before the EQs are overall higher than those after EQs, in addition both of them slightly increase with the earthquake magnitude. These results suggest that the anomalous variations of the GIM-TEC before the EQs might be related to the seismic activities.

scholarly journals Methods of detection of changes in the distribution of observed statistics of time derivatives of the total electron content because of cycle slips in navigation satellite’s signals

2019 ◽  
Vol 30 ◽  
pp. 15007
Author(s):  
George Minasyan ◽  
Ivan Nesterov ◽  
Yaroslav Ilyushin
Keyword(s):  
Total Electron Content ◽  
Satellite System ◽  
Electron Content ◽  
Total Electron ◽  
Cycle Slips ◽  
Phase Data ◽  
Total Electronic Content ◽  
Global Navigation Satellite ◽  
Electronic Content ◽  
Derivatives Of

Based on the analysis of the phase data of the global navigation satellite system, distributions of time derivatives of the L1 phase frequency and the total electronic content are obtained. The change in the distributions of observed statistics of time derivatives of the total electron content was analyzed, because there are cycle slips in signals of navigation satellites. According to the analysis of the statistics of the phase of signals, an assumption about the physical and technical reasons for phase failures was made. The correlation between time derivatives of the phase signals and the total electron content has been obtained, despite the apparent dependence of the latter on the phase of the signal. This ratio showed that neither direct nor inverse dependence of the change in the distribution of time derivatives in both of quantities was found.

scholarly journals Ionospheric corrections tailored to the Galileo High Accuracy Service

2021 ◽  
Vol 95 (12) ◽  
Author(s):  
A. Rovira-Garcia ◽  
C. C. Timoté ◽  
J. M. Juan ◽  
J. Sanz ◽  
G. González-Casado ◽  
...  
Keyword(s):  
Satellite Orbit ◽  
Satellite System ◽  
High Accuracy ◽  
Integer Ambiguity ◽  
Electron Content ◽  
Confidence Bounds ◽  
Total Electron ◽  
Phase Measurements ◽  
Model Geometry ◽  
Global Navigation Satellite

AbstractThe Galileo High Accuracy Service (HAS) is a new capability of the European Global Navigation Satellite System that is currently under development. The Galileo HAS will start providing satellite orbit and clock corrections (i.e. non-dispersive effects) and soon it will also correct dispersive effects such as inter-frequency biases and, in its full capability, ionospheric delay. We analyse here an ionospheric correction system based on the fast precise point positioning (Fast-PPP) and its potential application to the Galileo HAS. The aim of this contribution is to present some recent upgrades to the Fast-PPP model, with the emphasis on the model geometry and the data used. The results show the benefits of integer ambiguity resolution to obtain unambiguous carrier phase measurements as input to compute the Fast-PPP model. Seven permanent stations are used to assess the errors of the Fast-PPP ionospheric corrections, with baseline distances ranging from 100 to 1000 km from the reference receivers used to compute the Fast-PPP corrections. The 99% of the GPS and Galileo errors in well-sounded areas and in mid-latitude stations are below one total electron content unit. In addition, large errors are bounded by the error prediction of the Fast-PPP model, in the form of the variance of the estimation of the ionospheric corrections. Therefore, we conclude that Fast-PPP is able to provide ionospheric corrections with the required ionospheric accuracy, and realistic confidence bounds, for the Galileo HAS.

scholarly journals MONITORING OF IONOSPHERIC SCINTILLATION PHENOMENA USING SYNTHETIC APERTURE RADAR (SAR)

2018 ◽  
Vol IV-5 ◽  
pp. 331-337
Author(s):  
S. Mohanty ◽  
C. Carrano ◽  
G. Singh
Keyword(s):  
Satellite System ◽  
Synthetic Aperture ◽  
Ionospheric Scintillation ◽  
Electron Content ◽  
Data Sets ◽  
Low Frequencies ◽  
Total Electron ◽  
Gnss Receiver ◽  
Synthetic Aperture Radars ◽  
Global Navigation Satellite

<p><strong>Abstract.</strong> The applications of synthetic aperture radars (SAR) have increased manifold in the past decade, which includes numerous Earth observation applications such as agriculture, forestry, disaster monitoring cryospheric- and atmospheric- studies. Among them, the potential of SAR for ionospheric studies is gaining importance. The susceptibility of SAR to space weather dynamics, and ionosphere in particular, comes at low frequencies of L- and P-bands. This paper discusses one such scintillation event that was observed by L-band Advanced Land Observation Satellite (ALOS)-2 Phased Array L-type SAR (PALSAR) over southern India on March 23, 2015. The sensors also acquired data sets on four other days on which the ionosphere was quiet. Ionospheric parameter measurements of total electron content (TEC) and amplitude scintillation (S<sub>4</sub>) index from ground-based Global Navigation Satellite System (GNSS) receiver at Tirunelveli was used to establish the ionospheric conditions on the days of SAR acquisition as well as to corroborate the S<sub>4</sub> estimated from SAR. Multi-temporal ALOS-2 data sets were utilized to calculate S<sub>4</sub> from two separate methods and the results have a good agreement with GNSS receiver measurements. This highlights the potential of SAR as an alternate technique of monitoring ionospheric scintillations that can be utilized as complementary to the highly accurate and dedicated measurements from the GNSS networks.</p>

Comparative analysis of global ionospheric models used in GNSS data processing based on selected stations

2021 ◽  
Author(s):  
Paulina Woźniak ◽  
Anna Świątek ◽  
Leszek Jaworski
Keyword(s):  
Total Electron Content ◽  
Satellite System ◽  
Ionospheric Delay ◽  
Satellite Orbits ◽  
Electron Content ◽  
Free Electrons ◽  
Total Electron ◽  
Ionospheric Models ◽  
Station Coordinates ◽  
The Difference

&lt;p&gt;Among the many error sources affecting GNSS &lt;em&gt;(Global Navigation Satellite System)&lt;/em&gt; positioning accuracy, the ionosphere is the cause of those of the greatest value. The ionized gas layer, where also free electrons are present, extends from the upper atmosphere to 1,000 km above the Earth's surface (conventionally). As the GNSS satellite orbits altitude is more than 20,000 km, the wave transmitted from the satellite to the receiver on the Earth&amp;#8217;s ground passes through this layer, but not unscathed. The ionosphere is a dispersive medium for the electromagnetic waves in the microwave band, including UHF &lt;em&gt;(Ultra High Frequency)&lt;/em&gt; waves transmitted by GNSS satellites. As a result, the group velocity of the wave decreases, while its phase velocity &amp;#8211; increases.&lt;/p&gt;&lt;p&gt;Ionospheric delay compensation methods include among others multi-frequency measurements;&amp;#160; however, when considering measurements on one frequency, the usage of ionospheric models is an option. The key element is the number of free electrons, its inclusion in the course of calculations is possible thanks to the TEC &lt;em&gt;(Total Electron Content)&lt;/em&gt; maps. Taking into account the variability of the coefficient in the daily and annual course, as well as depending on the activity of the Sun and its 11-year cycle, it is important to use the current value for a given place and time.&lt;/p&gt;&lt;p&gt;For the European Galileo satellite system a dedicated ionospheric model NeQuick-G was developed. As a simple modification of the formula allows it to be applied to other satellite systems, it can be considered in a broader context, regardless of the system and receiver location. In our study the TEC maps published by IGS are used as the comparative data. As a reference, the station located in Warsaw, Poland, is adopted.&lt;/p&gt;&lt;p&gt;The subject of this research is the reliability and validity of the model in equatorial region. The analysis is performed for the stations belonging to the IGS &lt;em&gt;(International GNSS Service)&lt;/em&gt; network, located in the discussed area. For each hour of the day, independently for each month of 2019, statistic parameters are determined for both models as well as for the difference between them. The results are analysed taking into account the local time of individual stations. The decisive element is the comparison of the station position time series during disturbed and quiet ionospheric conditions (selected based on the K-index), using each of the models (single-frequency observations). The station coordinates are determined from GPS &lt;em&gt;(Global Positioning System)&lt;/em&gt; data using the PPP &lt;em&gt;(Precise Point Positioning)&lt;/em&gt; method; the position determined for the iono-free combination (dual-frequency observations) is used as a reference.&lt;/p&gt;&lt;p&gt;The ionospheric delay is directly proportional to the value of the TEC parameter. The difference between the models, exceeding on average even 20 TECU &lt;em&gt;(Total Electron Content Unit)&lt;/em&gt; during some periods, translates into a station coordinate differences. The presented analysis may indicate the need for local improvement of global ionospheric models in the discussed region, which will consequently affect the GNSS positioning quality.&lt;/p&gt;

A New Approach to Monitoring the Interplanetary Shock Induced Pulse: TEC Measurements by the GNSS Receiver Network

2020 ◽  
Author(s):  
Xingran Chen ◽  
Quanhan Li ◽  
Qiugang Zong ◽  
Yongqiang Hao
Keyword(s):  
Propagation Speed ◽  
Interplanetary Shock ◽  
Satellite System ◽  
Wave Form ◽  
Electron Content ◽  
Shock Pulse ◽  
Total Electron ◽  
New Approach ◽  
Gnss Receivers ◽  
Global Navigation Satellite

&lt;p&gt;We revisit the typical interplanetary shock event on November 7, 2004, with high resolution total electron content (TEC) measurements obtained by the distributed Global Navigation Satellite System (GNSS) receivers. TEC impulses were observed after the IP shock impinged on the dayside agnetosphere at ~18:27 UT. In view of the similarity of the wave form and the time-delay characteristics, the TEC impulses were regarded as responses to the IP shock, despite the small amplitude (in the order of 0.4 TECU). Particularly, the peak of the TEC impulse was first observed by the receivers located around 120&amp;#176;W geographic longitude (corresponding to noon magnetic local time), while receivers at both sides recorded the impulse sequentially afterwards. From the timedelay of the TEC impulse, we derive the propagation velocity of the shock induced pulse. The angular velocity of the pulse is estimated to be ~2 degree per second, which is in the same order as the propagation speed of a typical shock pulse in the magnetosphere. Our results present global observational features of the shock pulse and provide new aspects to understand the ionospheric-magnetospheric dynamics in response to IP shocks.&lt;/p&gt;

scholarly journals Correlation between Ionospheric TEC and the DCB Stability of GNSS Receivers from 2014 to 2016

2019 ◽  
Vol 11 (22) ◽  
pp. 2657 ◽  
Author(s):  
Choi ◽  
Sohn ◽  
Lee
Keyword(s):  
Estimation Method ◽  
Satellite System ◽  
Electron Content ◽  
Strong Positive Correlation ◽  
Low Latitude ◽  
Total Electron ◽  
Gnss Receiver ◽  
Gnss Receivers ◽  
Global Navigation Satellite ◽  
The Relationship

The Global Navigation Satellite System (GNSS) differential code biases (DCBs) are a major obstacle in estimating the ionospheric total electron content (TEC). The DCBs of the GNSS receiver (rDCBs) are affected by various factors such as data quality, estimation method, receiver type, hardware temperature, and antenna characteristics. This study investigates the relationship between TEC and rDCB, and TEC and rDCB stability during a three-year period from 2014 to 2016. Linear correlations between pairs of variables, measured with Pearson’s coefficient (), are considered. It is shown that the correlation between TEC and rDCB is the smallest in low-latitude regions. The mid-latitude regions exhibit the maximum value of. In contrast, the correlation between TEC and rDCB root mean square (RMS, stability) was greater in low-latitude regions. A strong positive correlation (R≥0.90) on average between TEC and rDCB RMS was also revealed at two additional GNSS stations in low-latitude regions, where the correlation shows clear latitudinal dependency. We found that the correlation between TEC and rDCB stability is still very strong even after replacing a GNSS receiver.

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