The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform

A. Laurence Gray - One of the best experts on this subject based on the ideXlab platform.

  • Reducing Ionospheric Electron Density errors in satellite radar interferometry applications
    Canadian Journal of Remote Sensing, 2002
    Co-Authors: Karim E. Mattar, A. Laurence Gray
    Abstract:

    It has been demonstrated that Ionospheric Electron Density disturbances can influence multi-pass satellite radar interferometry (SRI). This has been observed to occur near the magnetic poles, particularly during strong magnetic disturbances. Ionospheric disturbances most clearly appear in interferometric synthetic aperture radar (InSAR) as a kilometre-scale modulation in the azimuth pixel shift needed for optimal registration of the interferometric pair. This modulation (also known as "azimuth streaks") also affects the InSAR phase, and consequently such SRI applications as digital elevation model (DEM) generation and displacement measurement, and may appear as "streaks" in the coherence map. The effect is worse for L-band systems (e.g., Japanese Earth resources satellite 1 (JERS-1) and Phased array type L-band synthetic aperture radar (PALSAR)), but can be significant even at C band (e.g., European remote sensing satellites ERS-1/2 and RADARSAT I and II). The influence of Ionospheric effects on interfero...

  • Influence of Ionospheric Electron Density fluctuations on satellite radar interferometry
    Geophysical Research Letters, 2000
    Co-Authors: A. Laurence Gray, Karim E. Mattar, George J. Sofko
    Abstract:

    Evidence is presented that auroral zone Ionospheric disturbances can influence satellite radar interferometry (SRI) obtained with the RADARSAT, ERS and JERS-1 satellites. Fluctuations in Ionospheric Electron Density can lead to an azimuth shift modulation in synthetic aperture radar (SAR) imagery, which can be detected using SRI. Measurements of azimuth shift in SRI can help to differentiate Ionospheric from tropospheric propagation problems, and to understand better the impact of the ionosphere on spaceborne SAR. Further, SRI azimuth shift modulation may be useful in mapping patterns of polar auroral zone Ionospheric disturbances over large distances.

George J. Sofko - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Ionospheric Electron Density fluctuations on satellite radar interferometry
    Geophysical Research Letters, 2000
    Co-Authors: A. Laurence Gray, Karim E. Mattar, George J. Sofko
    Abstract:

    Evidence is presented that auroral zone Ionospheric disturbances can influence satellite radar interferometry (SRI) obtained with the RADARSAT, ERS and JERS-1 satellites. Fluctuations in Ionospheric Electron Density can lead to an azimuth shift modulation in synthetic aperture radar (SAR) imagery, which can be detected using SRI. Measurements of azimuth shift in SRI can help to differentiate Ionospheric from tropospheric propagation problems, and to understand better the impact of the ionosphere on spaceborne SAR. Further, SRI azimuth shift modulation may be useful in mapping patterns of polar auroral zone Ionospheric disturbances over large distances.

Debao Wen - One of the best experts on this subject based on the ideXlab platform.

  • Radio Occultation Measurements From the Australian Microsatellite FedSat
    IEEE Transactions on Geoscience and Remote Sensing, 2012
    Co-Authors: Robert J. Norman, Debao Wen, Peter. Dyson, Endawoke Yizengaw, J. Le Marshall, Chuan-sheng Wang, Brett Carter, Kefei Zhang
    Abstract:

    The Australian Low Earth Orbit (LEO) microsatellite, FedSat (named to commemorate the centenary of the Australian Federation in 2001), was launched into orbit on December 14, 2002 from the Tanegashima Space Centre, Japan. A Global Positioning System (GPS) receiver was one of the instruments onboard. The received GPS signals can be used to investigate the Ionospheric Electron Density and the atmosphere below FedSat's orbiting altitude, using radio occultation (RO) techniques. The RO technique developed involves a simplified form of the Abel transform using the slant total Electron content (STEC) determined from radio signals that traverse below FedSat's orbiting altitude. Electron Density profiles from the GPS RO data, recorded by the GPS receiver onboard the FedSat satellite, are determined for the first time. The technique combined with simultaneous occultation Density profile extraction from different LEO satellites and satellite navigation systems has the potential to image near real-time 3-D structures of the Ionospheric Electron Density.

  • Tomographic reconstruction of Ionospheric Electron Density based on constrained algebraic reconstruction technique
    GPS Solutions, 2010
    Co-Authors: Debao Wen, Sanzhi Liu, Pingying Tang
    Abstract:

    A constrained algebraic reconstruction technique (CART) is proposed for the tomographic reconstruction of the Ionospheric Electron Density distribution. The method uses a popular two-dimensional multi-point finite difference approximation of the second order Laplace operator to provide the constraint matrix. The tomographic results of a numerical simulation show that the reconstruction accuracy of Electron Density distribution is significantly improved. A careful validation of the reliability and superiority of CART is made. Finally, we applied the new method to the analysis of actual Global Navigation Satellite Systems (GNSS) observations and compared the results with ionosonde observation of Wuhan station.

  • GNSS-based tomographic reconstruction of the Ionospheric Electron Density distribution using a combined algorithm
    Current Science, 2010
    Co-Authors: Debao Wen, Kefei Zhang, N Edwards
    Abstract:

    An algorithm is proposed to image Ionospheric Electron Density (IED) distribution. In this method, generalized singular value decomposition (GSVD) is first used to resolve the ill-conditioned problem in the computerized Ionospheric tomography system. Its estimate is then provided as the initial approximation required by the improved algebraic reconstruction technique (IART). Numerical simulation has demonstrated that the combined algorithm is superior to both GSVD and IART for tomographic inversion of IED. Finally, the method is applied to perform inversion of IED using a set of global navigation satellite system (GNSS) data during a magnetically disturbed period. The reconstructed results reveal two prominent features of the ionosphere under the disturbed condition. The reliability of the method is also validated by the ionosonde data recorded at Wuhan station, China.

  • monitoring the three dimensional Ionospheric Electron Density distribution using gps observations over china
    Journal of Earth System Science, 2007
    Co-Authors: Debao Wen, Yunbin Yuan
    Abstract:

    In this paper, an IRI model assisted GPS-based Computerized Ionospheric Tomography (CIT) technique is developed to inverse the Ionospheric Electron Density (IED) distribution over China. Essentially, an improved algebraic reconstruction technique (IART) is first proposed to reconstruct the Ionospheric images with high resolution and high efficiency. A numerical experiment is used to validate the reliability of the method and its advantages to the classical algebraic reconstruction technique (ART). This is then used to reconstruct the IED images using the GPS data in China. The variations of the IED during magnetically quiet and disturbed days are reported and analyzed here. Reconstructed results during magnetically quiet days show some prominent Ionospheric features such as the development of equatorial anomaly and the tilt of ionization crest. Meanwhile, Ionospheric storm phase effects and disturbed features can also be revealed from the reconstructed IED image under storm conditions. Research shows that the positive storm phase effects usually happen in southern China, and the negative storm phase effects mainly occur in northern China. The equatorial anomaly crest moved to the north in the main phase of the storm. Ionosonde data recorded at Wuhan station provides the verification for the reliability of GPS-based CIT technique.

Karim E. Mattar - One of the best experts on this subject based on the ideXlab platform.

  • Reducing Ionospheric Electron Density errors in satellite radar interferometry applications
    Canadian Journal of Remote Sensing, 2002
    Co-Authors: Karim E. Mattar, A. Laurence Gray
    Abstract:

    It has been demonstrated that Ionospheric Electron Density disturbances can influence multi-pass satellite radar interferometry (SRI). This has been observed to occur near the magnetic poles, particularly during strong magnetic disturbances. Ionospheric disturbances most clearly appear in interferometric synthetic aperture radar (InSAR) as a kilometre-scale modulation in the azimuth pixel shift needed for optimal registration of the interferometric pair. This modulation (also known as "azimuth streaks") also affects the InSAR phase, and consequently such SRI applications as digital elevation model (DEM) generation and displacement measurement, and may appear as "streaks" in the coherence map. The effect is worse for L-band systems (e.g., Japanese Earth resources satellite 1 (JERS-1) and Phased array type L-band synthetic aperture radar (PALSAR)), but can be significant even at C band (e.g., European remote sensing satellites ERS-1/2 and RADARSAT I and II). The influence of Ionospheric effects on interfero...

  • Influence of Ionospheric Electron Density fluctuations on satellite radar interferometry
    Geophysical Research Letters, 2000
    Co-Authors: A. Laurence Gray, Karim E. Mattar, George J. Sofko
    Abstract:

    Evidence is presented that auroral zone Ionospheric disturbances can influence satellite radar interferometry (SRI) obtained with the RADARSAT, ERS and JERS-1 satellites. Fluctuations in Ionospheric Electron Density can lead to an azimuth shift modulation in synthetic aperture radar (SAR) imagery, which can be detected using SRI. Measurements of azimuth shift in SRI can help to differentiate Ionospheric from tropospheric propagation problems, and to understand better the impact of the ionosphere on spaceborne SAR. Further, SRI azimuth shift modulation may be useful in mapping patterns of polar auroral zone Ionospheric disturbances over large distances.

Jian Kong - One of the best experts on this subject based on the ideXlab platform.

  • Tomographic reconstruction of Ionospheric Electron Density during the storm of 5-6 August 2011 using multi-source data
    Scientific reports, 2015
    Co-Authors: Jun Tang, Yibin Yao, Liang Zhang, Jian Kong
    Abstract:

    The insufficiency of data is the essential reason for ill-posed problem existed in computerized Ionospheric tomography (CIT) technique. Therefore, the method of integrating multi-source data is proposed. Currently, the multiple satellite navigation systems and various Ionospheric observing instruments provide abundant data which can be employed to reconstruct Ionospheric Electron Density (IED). In order to improve the vertical resolution of IED, we do research on IED reconstruction by integration of ground-based GPS data, occultation data from the LEO satellite, satellite altimetry data from Jason-1 and Jason-2 and ionosonde data. We used the CIT results to compare with incoherent scatter radar (ISR) observations, and found that the multi-source data fusion was effective and reliable to reconstruct Electron Density, showing its superiority than CIT with GPS data alone.

  • application of hybrid regularization method for tomographic reconstruction of midlatitude Ionospheric Electron Density
    Advances in Space Research, 2013
    Co-Authors: Yibin Yao, Jun Tang, Jian Kong, Liang Zhang, Shun Zhang
    Abstract:

    Abstract Reconstructing Ionospheric Electron Density (IED) is an ill-posed inverse problem, with classical Tikhonov regularization tending to smooth IED structures. By contrast, total variation (TV) regularization effectively resists noise and preserves discontinuities of the IED. In this paper, we regularize the inverse problem by incorporating both Tikhonov and TV regularization. A specific formulation of the proposed method, called hybrid regularization, is introduced and investigated. The method is then tested using simulated data for the actual positions of the GPS satellites and ground receivers, and also applied to the analysis of real observation data under quiescent and disturbed Ionospheric conditions. Experiments demonstrate the effectiveness, and illustrate the validity and reliability of the proposed method.