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Journal ArticleDOI

A survey of ionospheric effects on space-based radar

01 Apr 2004-Waves in Random Media (Taylor & Francis)-Vol. 14, Iss: 2
TL;DR: In this paper, a survey of the potential ionospheric effects on the performance of space-based radar systems (SBRs) operating in the ambient ionosphere environment is presented.
Abstract: In this survey, we fully review almost all potential ionospheric effects on the performance of space-based radar systems (SBRs), which operate in the ambient ionosphere environment; in particular, we review the use of space-based synthetic aperture radar systems (SARs) for imaging. There are two families of effects involved. One is the effects of the background ionosphere (non-turbulent ionosphere), such as dispersion, group delay, refraction, Faraday rotation, and phase shift. The other is the effects due to ionospheric irregularities, such as refractive index fluctuation, phase perturbation, angle-of-arrival fluctuation, pulse broadening, clutter, and amplitude scintillation. These effects adversely affect SAR imaging in several respects, such as by causing image shift in the range, and degradations of the range resolution, azimuthal resolution, and/or the resolution in height (elevation). We also review ionospheric irregularity characteristics and descriptions, propagation channel statistics, ...
Citations
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Journal ArticleDOI
TL;DR: This paper provides first a tutorial about the SAR principles and theory, followed by an overview of established techniques like polarimetry, interferometry and differential interferometric as well as of emerging techniques (e.g., polarimetric SARinterferometry, tomography and holographic tomography).
Abstract: Synthetic Aperture Radar (SAR) has been widely used for Earth remote sensing for more than 30 years. It provides high-resolution, day-and-night and weather-independent images for a multitude of applications ranging from geoscience and climate change research, environmental and Earth system monitoring, 2-D and 3-D mapping, change detection, 4-D mapping (space and time), security-related applications up to planetary exploration. With the advances in radar technology and geo/bio-physical parameter inversion modeling in the 90s, using data from several airborne and spaceborne systems, a paradigm shift occurred from the development driven by the technology push to the user demand pull. Today, more than 15 spaceborne SAR systems are being operated for innumerous applications. This paper provides first a tutorial about the SAR principles and theory, followed by an overview of established techniques like polarimetry, interferometry and differential interferometry as well as of emerging techniques (e.g., polarimetric SAR interferometry, tomography and holographic tomography). Several application examples including the associated parameter inversion modeling are provided for each case. The paper also describes innovative technologies and concepts like digital beamforming, Multiple-Input Multiple-Output (MIMO) and bi- and multi-static configurations which are suitable means to fulfill the increasing user requirements. The paper concludes with a vision for SAR remote sensing.

1,614 citations

Journal ArticleDOI
TL;DR: A short review is presented on the recent trend and development of SAR and related techniques with selected topics, including the fields of applications, specifications of airborne and spaceborne SARs, and information contents in and interpretations of amplitude data, interferometric SAR (InSar) data, and polarimetric SAR (PolSAR) data.
Abstract: The present article is an introductory paper in this special issue on synthetic aperture radar (SAR). A short review is presented on the recent trend and development of SAR and related techniques with selected topics, including the fields of applications, specifications of airborne and spaceborne SARs, and information contents in and interpretations of amplitude data, interferometric SAR (InSAR) data, and polarimetric SAR (PolSAR) data. The review is by no means extensive, and as such only brief summaries of of each selected topics and key references are provided. For further details, the readers are recommended to read the literature given in the references theirin.

235 citations

Journal ArticleDOI
TL;DR: In this paper, satellite-based interferometric synthetic aperture radar (InSAR) was used to make the first systematic search for deformation in all volcanic arcs of Latin America (including Mexico, Central America, the Caribbean, and the northern and southern Andes), spanning 2006-2008.
Abstract: [1] We combine new observations of volcano deformation in Latin America with more than 100 previous deformation studies in other areas of the world to constrain the frequency, magnitude, and duration of subaerial volcano deformation events. We discuss implications for eruptive hazards from a given deformation event and the optimum repeat interval for proposed InSAR satellite missions. We use L band (23.6 cm wavelength) satellite-based interferometric synthetic aperture radar (InSAR) to make the first systematic search for deformation in all volcanic arcs of Latin America (including Mexico, Central America, the Caribbean, and the northern and southern Andes), spanning 2006–2008. We combine L and C band (5.6 cm wavelength) InSAR observations over the southern Andes volcanoes to extend the time series from 2002 to 2008 and assess the capabilities of the different radars: L band gives superior results in highly vegetated areas. Our observations reveal 11 areas of volcano deformation, some of them in areas that were thought to be dormant. There is a lack of observed deformation at several erupting volcanoes, probably due to temporal aliasing. The total number of deforming volcanoes in the central and southern Andes now totals 15 (from observations between 1992 and 2008), comparable to the Alaska/Aleutian arc. Globally, volcanoes deform across a variety of time scales (from seconds to centuries) often without eruption and with no apparent critical observation time scale, although observations made every minute are sometimes necessary to see precursors to eruption.

162 citations

Journal ArticleDOI
TL;DR: Improved coherence combined with similar or better accuracy and resolution suggests that L-band ALOS will outperform C-band ERS in the recovery of slow crustal deformation.
Abstract: We assess the spatial resolution and phase noise of interferograms made from L-band Advanced Land Observing Satellite (ALOS) synthetic-aperture-radar (SAR) data and compare these results with corresponding C-band measurements from European Space Agency Remote Sensing Satellite (ERS). Based on cross-spectral analysis of phase gradients, we find that the spatial resolution of ALOS interferograms is 1.3times better than ERS interferograms. The phase noise of ALOS (i.e., line-of-sight precision in the 100-5000-m wavelength band) is 1.6times worse than ERS (3.3 mm versus 2.1 mm). In both cases, the largest source of error is tropospheric phase delay. Vector deformation maps associated with the June 17, 2007 (Father's day) intrusion along the east rift zone of the Kilauea Volcano were recovered using just four ALOS SAR images from two look directions. Comparisons with deformation vectors from 19 continuous GPS sites show rms line-of-site precision of 14 mm and rms azimuth precision (flight direction) of 71 mm. This azimuth precision is at least 4times better than the corresponding measurements made at C-band. Phase coherence is high even in heavily vegetated areas in agreement with previous results. This improved coherence combined with similar or better accuracy and resolution suggests that L-band ALOS will outperform C-band ERS in the recovery of slow crustal deformation.

155 citations


Cites background from "A survey of ionospheric effects on ..."

  • ...As discussed earlier, we expect a significant new (not usually evident at C-band) error contribution from the ionosphere [10], [11]....

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Journal ArticleDOI
TL;DR: The results show how the split-spectrum method is able to systematically compensate the ionospheric phase in interferograms, with the expected accuracy, and can therefore be a valid element of the operational processor.
Abstract: The differential ionospheric path delay is a major error source in L-band interferograms. It is superimposed to topography and ground deformation signals, hindering the measurement of geophysical processes. In this paper, we proceed toward the realization of an operational processor to compensate the ionospheric effects in interferograms. The processor should be robust and accurate to meet the scientific requirements for the measurement of geophysical processes, and it should be applicable on a global scale. An implementation of the split-spectrum method, which will be one element of the processor, is presented in detail, and its performance is analyzed. The method is based on the dispersive nature of the ionosphere and separates the ionospheric component of the interferometric phase from the nondispersive component related to topography, ground motion, and tropospheric path delay. We tested the method using various Advanced Land Observing Satellite Phased-Array type L-band synthetic aperture radar interferometric pairs with different characteristics: high to low coherence, moving and nonmoving terrains, with and without topography, and different ionosphere states. Ionospheric errors of almost 1 m have been corrected to a centimeter or a millimeter level. The results show how the method is able to systematically compensate the ionospheric phase in interferograms, with the expected accuracy, and can therefore be a valid element of the operational processor.

141 citations


Cites background from "A survey of ionospheric effects on ..."

  • ...In SAR interferograms, topography and ground deformation signals are mixed with ionospheric disturbances [1]....

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References
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Book
01 Jan 1965
TL;DR: This chapter discusses the concept of a Random Variable, the meaning of Probability, and the axioms of probability in terms of Markov Chains and Queueing Theory.
Abstract: Part 1 Probability and Random Variables 1 The Meaning of Probability 2 The Axioms of Probability 3 Repeated Trials 4 The Concept of a Random Variable 5 Functions of One Random Variable 6 Two Random Variables 7 Sequences of Random Variables 8 Statistics Part 2 Stochastic Processes 9 General Concepts 10 Random Walk and Other Applications 11 Spectral Representation 12 Spectral Estimation 13 Mean Square Estimation 14 Entropy 15 Markov Chains 16 Markov Processes and Queueing Theory

13,886 citations


Additional excerpts

  • ...The fourth-order moment is obtained by using the following wellknown relationship (Papoulis 1965) for four stochastic Gaussian variables: 〈x1x2x∗3 x∗4 〉 =〈x1x∗3 〉〈x2x∗4 〉+ 〈x1x∗4 〉〈x2x∗3 〉+ 〈x1x2〉〈x∗3 x∗4 〉....

    [...]

Book
01 Jan 2002
TL;DR: In this paper, the meaning of probability and random variables are discussed, as well as the axioms of probability, and the concept of a random variable and repeated trials are discussed.
Abstract: Part 1 Probability and Random Variables 1 The Meaning of Probability 2 The Axioms of Probability 3 Repeated Trials 4 The Concept of a Random Variable 5 Functions of One Random Variable 6 Two Random Variables 7 Sequences of Random Variables 8 Statistics Part 2 Stochastic Processes 9 General Concepts 10 Random Walk and Other Applications 11 Spectral Representation 12 Spectral Estimation 13 Mean Square Estimation 14 Entropy 15 Markov Chains 16 Markov Processes and Queueing Theory

12,407 citations

Book
01 Jan 1978
TL;DR: This IEEE Classic Reissue presents a unified introduction to the fundamental theories and applications of wave propagation and scattering in random media and is expressly designed for engineers and scientists who have an interest in optical, microwave, or acoustic wave propagate and scattering.
Abstract: A volume in the IEEE/OUP Series on Electromagnetic Wave Theory Donald G. Dudley, Series Editor This IEEE Classic Reissue presents a unified introduction to the fundamental theories and applications of wave propagation and scattering in random media. Now for the first time, the two volumes of Wave Propagation and Scattering in Random Media previously published by Academic Press in 1978 are combined into one comprehensive volume. This book presents a clear picture of how waves interact with the atmosphere, terrain, ocean, turbulence, aerosols, rain, snow, biological tissues, composite material, and other media. The theories presented will enable you to solve a variety of problems relating to clutter, interference, imaging, object detection, and communication theory for various media. This book is expressly designed for engineers and scientists who have an interest in optical, microwave, or acoustic wave propagation and scattering. Topics covered include:

5,877 citations


"A survey of ionospheric effects on ..." refers background or methods in this paper

  • ...…the path, r0n the distance from the receiver to r0, ψd and ψu the downward and upward path complex phase fluctuations due to ionospheric turbulence (Fante 1985, Ishimaru 1997), di = ∫ ds is the ionospheric thickness along the path, and 0 gives the azimuthal resolution ( y ′), as shown in figure 10....

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  • ...Therefore, the resulting correlation function may be modelled as a frequency coherence function given by Knepp and Reinking (1989), Ishimaru (1997): CSS( fd) = 〈S( f )S( f + fd)〉 − 〈S〉2, (5.29) where S is assumed to be a stationary process over the frequency range of interest....

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  • ...There are available several books (Ishimaru 1978, 1997, Tatarskii 1971, Tatarskii et al 1993, Uscinski 1977), some earlier investigations (Shishov 1973, 1974, Fante 1974, 1980a, 1981, Hong and Ishimaru 1976, Hong et al 1977, Ishimaru 1975, Ishimaru and Hong 1975, Knepp 1983a, 1983b, Liu et al 1974,…...

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  • ...…equation (5.4), we see that the variance of the refractive index fluctuation due to the ionospheric turbulence is approximately proportional to f −4 (Ishimaru 1997), and this can reduce the coherent length of the wavefield below the effective aperture size of SAR, and thus the azimuthal resolution…...

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  • ...This conventional view is confirmed by transport theory (radiative transfer theory) (Ishimaru 1978, 1997)....

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Journal ArticleDOI
01 Mar 2000
TL;DR: In this paper, the authors present a review of the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering, including cartography, geodesy, land cover characterization, and natural hazards.
Abstract: Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristic of the surface. By exploiting the phase of the coherent radar signal, interferometry has transformed radar remote sensing from a largely interpretive science to a quantitative tool, with applications in cartography, geodesy, land cover characterization, and natural hazards. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

3,042 citations


"A survey of ionospheric effects on ..." refers background or methods in this paper

  • ...Chirp signals are widely used in high-performance radar applications for pulse compression (e.g. Rosen et al 2000)....

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  • ...The technical challenges and the applications of SAR interferometry (InSAR) for topographic mapping and deformation measurements from space have developed dramatically since the beginning of the 1990s (Gens and van Genderen 1996, Bamler and Hartl 1998, Rosen et al 2000)....

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  • ...…radar frequency (e.g. greater than 50 m ionospheric path delay at the L-band) and can be quite substantial in the difference phase that produces the interferogram (many centimetres of differential tropospheric delay, and metre-level ionospheric contributions at low frequencies) (Rosen et al 2000)....

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Book ChapterDOI
Minoru Nakagami1
01 Jan 1960
TL;DR: In this article, the authors summarized the principal results of a series of statistical studies in the last seven years on the intensity distributions due to rapid fading, and presented an extremely simplified method for estimating the improvement available from various systems of diversity reception.
Abstract: This paper summarizes the principal results of a series of statistical studies in the last seven years on the intensity distributions due to rapid fading The method of derivation and the principal characteristics of the m-distribution, originally found in our hf experiments and described by the author, are outlined Its applicability to both ionospheric and tropospheric modes of propagation is fairly well confirmed by some observations Its theoretical background is also discussed in detail A theoretical interpretation of the log-normal distribution is given on the basis of this formula An extremely simplified method is presented for estimating the improvement available from various systems of diversity reception The mutual dependences between the m-formula and other basic distributions are fully discussed Some generalized forms of the basic distributions are also investigated in relation to the m-formula Two methods of approximating a given function with the m-distribution are shown The joint distribution of two variables, each of which follows the m-distribution, is derived in two different ways Based on this, some useful associated distributions are also discussed

2,441 citations


"A survey of ionospheric effects on ..." refers background in this paper

  • ...(3.9) This can be expressed in terms of the one-way scintillation index, Sm (Nakagami 1960): S2m = m−1 = 〈(|eu|2 − 〈|eu|2〉)2〉....

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  • ...Nakagami (1960) summarized the derivation and principal characteristics of the m-distribution, which describes the intensity distributions due to rapid fading, and its applicability to both ionospheric and tropospheric modes of propagation has been fairly well confirmed by many observations....

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  • ...According to the Nakagami-m distribution, m is a positive number not less than 0.5, and m = 1 for a Rayleigh distribution (Nakagami 1960)....

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  • ...…distribution, for this case the PDF of the fluctuations of the S254 Z-W Xu et al received power caused by the disturbed propagation channel takes the form of equation (5.10) (Nakagami 1960, Knepp and Reinking 1989): p1(S) = m m Sm−1 (m)〈S〉m exp (−mS 〈S〉 ) , S 0, (5.14) where 〈S〉 is the mean value....

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