Compared with traditional simultaneous algebraic reconstruction, this method facilitates. Robertson and gerald l mader national geodetic survey, nosnoaa and cooperative institute for research in environmental sciences cires and noaa space environment center university of coloradonoaa, boulder, colorado 803090216, usa. Alternating minimization algorithms for transmission tomography joseph a. The nature of these limitations is described in this paper. The tec, which is the main input to cit, is defined. Constrained simultaneous algebraic reconstruction technique. Convergent incremental optimization transfer algorithms. Tomographic reconstruction of the ionosphere using ground.
Some inversion techniques are based on 2 minimization algorithms i. Orthogonal decomposition framework for ionospheric tomography algorithms orthogonal decomposition framework for ionospheric tomography algorithms sutton, eric. According to the actual detecting condition of sparse receiver and limited projecting angle, polynomial interpolation method and projecting angle expansion method. Tomographic analysis of ionosphere and plasmasphere. A modified threedimensional ionospheric tomography algorithm. In order to cope with such illconditioning, a new tomographic algorithm, termed twostep algorithm tsa, is presented. This paper presents a modelindependent algorithm for tomography of the. Dissertations and theses electrical and computer engineering. Prior knowledge consists of the following pieces of information. Department of geomatics engineering the university of calgary calgary, alberta, canada t2n 1n4. Ionospheric tomography inverse algorithms are usually an illconditioned problem because the geometric distribution of continuously operating reference gps stations is not ideal for this task. A modelindependent algorithm for ionospheric tomography.
Ionospheric imaging using computerized tomography ideals. This new method is called ionospheric tomography based on the neural network itnn. A new ionospheric estimation algorithm for sbas combining. Na, hua lee, and jian shen tomographic imaging of the ionosphere using bidirectional extrapolation algorithm, proc. Application of generalized singular value decomposition to. Global positioning system gps radio occultation signals received by a low earth orbit leo satellite provide information about the global distribution of electron density in the ionosphere. Precise ionosphere modeling using regional gps network data. At present, in the problems of ray radio tomography of the ionosphere, iterative algorithms are most popular, although noniterative algorithms are also used. Tomographic reconstruction is a type of multidimensional inverse problem where the challenge is to yield an estimate of a specific system from a finite number of projections. Algorithms and basis functions in tomographic reconstruction. We applied the computerized ionospheric tomography cit algorithm to the tec dataset from this gps network for monitoring the regional ionosphere over. In ionospheric tomography, when used to reconstruct the electron density pro. Due to the nonuniform and sparsity of ground gnss observation stations, the input data of the.
Pdf our work addresses ionospheric radio tomography rt based on the low orbital lo and high orbital ho navigational systems and the radio. To resolve it, an adaptive smoothness constraint ionospheric tomography algorithm is proposed in this work. A new twostep algorithm for ionospheric tomography solution. Adaptive smoothness constraint ionospheric tomography algorithm. I is the brightness in units of rayleighs megaphotons s. Simulation studies on the tomographic reconstruction of. According to the actual detecting condition of sparse receiver and limited projecting angle, polynomial interpolation method and projecting angle expansion. On the other hand, the performance of the existing reconstruction algorithms based on the adaptive adjustment of the relaxation parameters needs to be further improved. Ionospheric tomography algorithms, international journal of. A new ionospheric tomographic algorithm taking into. Computerized ionospheric tomography algorithms traditionally ignore the time variations of ionospheric distributions. At first sight, tomography appears to be the right choice. Fullorbit ultraviolet ionospheric tomography and applications.
Pdf time varying computerized ionospheric tomography. The test cases chosen make use of experimental electron content observations obtained from a meridional chain of receivers in scandinavia at times when the european incoherent scatter radar facility provided independent measurements of electron density for. The new algorithm performs an adaptive adjustment for the constrained weight coefficients of the tomography system. A notable example of applications is the reconstruction of computed tomography ct where crosssectional images of patients are obtained. The ionosphere, as a medium for radio wave propagation, essentially influences the operation. Tomographic reconstruction of ionospheric electron density during the storm of 56 august 2011 using multisource data skip to main content thank you for visiting. Stanford university abstract one can divide the existing ionospheric methods for sbas in two categories. Rowaction methods for huge and sparse systems and their. Adaptive smoothness constraint ionospheric tomography. To overcome this geometric deficiency, constraints or initial conditions of the ionosphere are imposed in the reconstruction method wen et al. Ionospheric tomography reconstruction based on global navigation satellite system observations is usually an illposed problem. To test the accuracy of the ionospheric tomography algorithms, a truth ionosphere is needed, with an associated data set of gnss tecmeasurements.
A new approach is proposed for cit that aims to permit sparsity in the reconstruction coef. Tikhonov regularization and a standard approach is implemented here using spherical harmonics as a reference to compare the new method. A hybrid reconstruction algorithm for 3d ionospheric. A comparison of reconstruction techniques used in ionospheric. A case of study in a geomagnetic storm shuanggen jin1 and rui jin1, 2 1 shanghai astronomical observatory, chinese academy of sciences, shanghai 200030, china 2 graduate university of the chinese academy of sciences, beijing 49, china email. Applying the technique of computer tomography to ionosphere detection, computerized ionospheric tomography cit can produce the large scale distribution of electron density in a two dimentional longitudinal section of ionosphere. Numerical simulations to assess art and mart performance for. Computerized tomography provides valuable information for imaging the ionospheric electron density distribution. Owing to the system configuration, the resolving capability of these systems is still limited. In addition, a unified discussion of some of the various reconstruction algorithms is presented. Tomographic algorithms direct inversion discrete inverse theory dit many different mathematical techniques have been used by different workers finding an appropriate background ionosphere to initialise any algorithm is the key to ionospheric tomography use extension of dit method of fremouw et al.
A hybrid reconstruction algorithm for 3d ionospheric tomography debao wen, yunbin yuan, jikun ou, kefei zhang, and kai liu abstractin this paper, a hybrid reconstruction algorithm hra is presented to solve the illposed inverse problem associated with 3d ionospheric stochastic tomography. For emissions produced by radiative recombination of electrons. Reconstruction algorithm of computerized ionospheric. Related electron energization in the ionosphere and the plasma sheet. The midas algorithms are based upon the oceanographic imaging techniques of munk and wunsch 1979. Regardless of the tomographic algorithm in use, the infor mation provided by satellite to ground measurements is poor. The mathematical basis for tomographic imaging was laid down by johann radon. Development and applications of ionospheric tomography. Sensors 2020, 20, 2404 3 of 17 is the length of the th path in the th voxel. Development and applications of ionospheric tomography ideals. Computerized ionospheric tomography cit is a technique to reconstruct the 2d, 3d or 4d ionospheric images bust and mitchell, 2008, razin, 2016.
Since existing algorithms are static reconstruction algorithms, the motion of the ionosphere becomes a source of image. Electron density profiles derived from groundbased gps. Read ionospheric tomography algorithms, international journal of imaging systems and technology on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Precise ionosphere modeling using regional gpsnetwork data. In this study, a set of basis functions and reconstruction algorithms are used to investigate best fitting two dimensional tomographic images of ionosphere electron density in height and latitude for one satellite and one receiver pair. A new twostep algorithm for ionospheric tomography. Computerized ionospheric tomography with the iri model. Ionosphere tomography is a typical illposed problem, and using the ionosphere priori information as the constraints to improve the state of normal equation is an effective approach to solve this. However, the efficiency of the ionospheric tomography is an issue. Algorithms and basis functions in tomographic reconstruction of ionospheric electron density ersin yavuz 1, feza ar. A modified threedimensional ionospheric tomography. Meanwhile, some efficient algorithms have been proposed to improve the accuracy and resolution of the reconstructed ionospheric images 20,21. An improved iterative algorithm for ionospheric tomography.
Pdf an improved iterative algorithm for ionospheric. Tomographic imaging of the ionosphere using bidirectional. Abstract an improved ionospheric tomography algorithm is developed for the tomographic reconstruction of the ionospheric electron density. Using sparse regularization for multiresolution tomography. A simple and relatively fast method csart is presented for tomographic reconstruction of the electron density distribution in the ionosphere using smooth fields. A realistic simulation framework to evaluate ionospheric. Previous studies mainly focused on improving inversion algorithms to solve the illposed inversion functions, but they cannot be applied generally, moreover, the illposed problem has not been solved radically.
The threedimensional ionospheric tomography algorithm with side rays was first presented in 2016 and applied to gnss water vapor tomography yao et al. State key laboratory of geodesy and earths dynamics, institute of geodesy and geophysics, chinese academy of sciences, wuhan 430077, china. A new ionospheric estimation algorithm for sbas combining kriging and tomography juan blanch, todd walter, and per enge. Huo xingliang 1, yuan yunbin 1, ou jikun 1, li ying 1, li zishen 2, wang ningbo 1. Ionospheric tomography algorithms, international journal. In this paper, a regional ionospheric mapping and tomography rimt tool was developed, which can be used to retrieve 2d tec and 3d ionospheric electron density profiles using groundbased or spaceborne gps measurements.
Computerized tomography ct techniques can be used to produce a twodimensional image of the electron density in the ionosphere. To the lower ionosphere, occhipinti setted up a new method based on the raytracing tool tdr to invert the propagation time. This paper presents a modelindependent algorithm for tomography of the ionosphere. In this paper, a new fourier domain reconstruction algorithm is presented which utilizes the information contained in the known region of the spectrum to estimate the frequency samples in the missingcone area. Since it does not use matrix algebra, it can be implemented in a lowlevel programming language, which speeds up applications significantly. Introduction investigationsof ionospheric spatial plasma distributions are necessary in order to study the ionosphere and the physics of its processes.
Reconstruction algorithm of computerized ionospheric tomography. There are numerous algorithms, both direct and iterative, that solve sles 4 and 5. This was conventional tomographic imaging where the line integral data were approximated into a plane and inverted to reveal the electron density. This paper presents a new ionospheric reconstruction algorithm called the residual correction method rcm. In satellite radio tomography, now commonly referred to as computerized ionospheric tomography cit, total electron content tec measurements are inverted and reconstructed to obtain a twodimensional electron density profile. The rcm is a fast, efficient, and numerically stable ionospheric tomography algorithm. Ionospheric data assimilation methods for geodetic applications paul s. We examine two radio occultation inversion algorithms. Twodimensional ionospheric tomography over the low. We then discuss the use of tikhonov 1963 regularization in all four algorithms gcgls, mart,rl, and lspd and pre. In the problem of imaging a patient we shone xrays through their body.
Pdf ionospheric tomography using navigation systems. A hybrid reconstruction algorithm for 3d ionospheric tomography. The study highlights the critical role of the range of the background input to the algorithms. Ionospheric data assimilation methods for geodetic. Alternating minimization algorithms for transmission. Thus, the observation equationobtainedusingdualfrequencycodemeasurements. Electronic systems and signals research laboratory department of electrical and systems engineering washington university st. Since the sle is underdetermined, we incorporate a prior information initial guess through the use of local time dependent empirical orthogonal functions eofs derived from international reference ionosphere iri2016 model. Analysis and validation of gpsmet radio occultation data. Orthogonal decomposition framework for ionospheric tomography. Rowaction methods for huge and sparse systems and their applications.
Computerized ionospheric tomography with the iri model orhan arikan a, feza arikan b, cemil b. Erol c a bilkent university, department of electrical and electronics engineering, bilkent ankara 06800, turkey b hacettepe university, department of electrical and electronics engineering, beytepe ankara 06800, turkey c tubitak uekae, kavaklidere, ankara 06100, turkey. An improved ionospheric tomography algorithm is developed for the tomographic reconstruction of the ionospheric electron density distribution based on the automatic search technology of relaxation. A density value at a single grid cell provides sufficient additional a priori information to constrain the imaging of a horizontally stratified ionosphere. Therefore, it is very necessary to develop an ionospheric tomography algorithm with high ef.
This paper compares the performance of three different reconstruction algorithms used for tomographic imaging of the ionosphere. Usually the voxel technique needs less gps measurements to model than the tomography technique required. However, the single layer model only reflects the variation of the ionosphere in the horizontal plane but neglects the variation along the altitude. Aug 12, 2015 tomographic reconstruction of ionospheric electron density during the storm of 56 august 2011 using multisource data skip to main content thank you for visiting. This absolute phase approach to the ray tomography of the ionosphere suffers from the problem of. Application of generalized singular value decomposition to ionospheric tomography k. Satellite radio probing and radio tomography of the ionosphere.
A new ionospheric tomographic algorithm taking into account the variation of the ionosphere. We use a wavelet neural network with a particle swarm optimization training algorithm to solve pixelbased ionospheric tomography. Therefore the former method usually method has higher time resolution than the latter one. Ionospheric correction using tomography stanford university. Spie 2027, advanced signal processing algorithms, architectures, and implementations iv. In other words, no particular algorithm is able to give a unique solution to the problem of ionospheric tomography. The necessary data are transionospheric satellite beacon total electron content tec data recorded simultaneously at multiple ground stations. Erol c a bilkent university, department of electrical and electronics engineering, bilkent ankara 06800, turkey b hacettepe university, department of electrical and electronics engineering, beytepe ankara 06800, turkey. A new ionospheric tomographic algorithm indian academy of.
As a result, the ionosphere tomography method would allow for more precise exploration of the ionospheric characteristics and. Ionosphere tomography using wavelet neural network and. These tecmeasurements can be inverted using a tomographic algorithm, after which the reconstructions can be compared with the truth to assess accuracy. A notable example of applications is the reconstruction of computed tomography ct where. This item appears in the following collections graduate dissertations and theses at illinois graduate theses and dissertations at illinois. Pdf tomography reconstruction of ionospheric electron density. A new ionospheric tomographic algorithm constrained multiplicative algebraic reconstruction technique cmart. Ionospheric total electron content tec measurements, obtained simultaneously at several locations, can be processed using computerized tomography ct algorithms to. Bayesian statistical ionospheric tomography improved by. Gridbased tomography, electron density, ionospheric profile, chapman function, gnss. In this paper, isr scans are used to produce computer representations of the ionosphere that are then used to test an ionospheric imaging algorithm, with the aim of evaluating the accuracy and.
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