The Experts below are selected from a list of 16902 Experts worldwide ranked by ideXlab platform
J W Holt - One of the best experts on this subject based on the ideXlab platform.
-
along track focusing of Airborne Radar sounding data from west antarctica for improving basal reflection analysis and layer detection
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: M E Peters, D D Blankenship, S P Carter, Scott D Kempf, Duncan A Young, J W HoltAbstract:This paper presents focused synthetic aperture Radar (SAR) processing of Airborne Radar sounding data acquired with the High-Capability Radar Sounder system at 60 MHz. The motivation is to improve basal reflection analysis for water detection and to improve layer detection and tracking. The processing and reflection analyses are applied to data from Kamb Ice Stream, West Antarctica. The SAR processor correlates the Radar data with reference echoes from subsurface point targets. The references are 1-D responses limited by the pulse nadir footprint or 2-D responses that include echo tails. Unfocused SAR and incoherent integration are included for comparison. Echoes are accurately preserved from along-track slopes up to about 0.5deg for unfocused SAR, 3deg for 1-D correlations, and 10deg for 2-D correlations. The noise/clutter levels increase from unfocused SAR to 1-D and 2-D correlations, but additional gain compensates at the basal interface. The basal echo signal-to-noise ratio improvement is typically about 5 dB, and up to 10 dB for 2-D correlations in rough regions. The increased noise degrades the clarity of internal layers in the 2-D correlations, but detection of layers with slopes greater than 3deg is improved. Reflection coefficients are computed for basal water detection, and the results are compared for the different processing methods. There is a significant increase in the detected water from unfocused SAR to 1-D correlations, indicating that substantial basal water exists on moderately sloped interfaces. Very little additional water is detected from the 2-D correlations. The results from incoherent integration are close to the focused SAR results, but the noise/clutter levels are much greater.
-
along track focusing of Airborne Radar sounding data from west antarctica for improving basal reflection analysis and layer detection
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: M E Peters, D D Blankenship, S P Carter, Scott D Kempf, Duncan A Young, J W HoltAbstract:This paper presents focused synthetic aperture Radar (SAR) processing of Airborne Radar sounding data acquired with the High-Capability Radar Sounder system at 60 MHz. The motivation is to improve basal reflection analysis for water detection and to improve layer detection and tracking. The processing and reflection analyses are applied to data from Kamb Ice Stream, West Antarctica. The SAR processor correlates the Radar data with reference echoes from subsurface point targets. The references are 1-D responses limited by the pulse nadir footprint or 2-D responses that include echo tails. Unfocused SAR and incoherent integration are included for comparison. Echoes are accurately preserved from along-track slopes up to about 0.5deg for unfocused SAR, 3deg for 1-D correlations, and 10deg for 2-D correlations. The noise/clutter levels increase from unfocused SAR to 1-D and 2-D correlations, but additional gain compensates at the basal interface. The basal echo signal-to-noise ratio improvement is typically about 5 dB, and up to 10 dB for 2-D correlations in rough regions. The increased noise degrades the clarity of internal layers in the 2-D correlations, but detection of layers with slopes greater than 3deg is improved. Reflection coefficients are computed for basal water detection, and the results are compared for the different processing methods. There is a significant increase in the detected water from unfocused SAR to 1-D correlations, indicating that substantial basal water exists on moderately sloped interfaces. Very little additional water is detected from the 2-D correlations. The results from incoherent integration are close to the focused SAR results, but the noise/clutter levels are much greater.
-
echo source discrimination in single pass Airborne Radar sounding data from the dry valleys antarctica implications for orbital sounding of mars
Journal of Geophysical Research, 2006Co-Authors: J W Holt, M E Peters, Scott D Kempf, David L Morse, D D BlankenshipAbstract:The interpretation of Radar sounding data from Mars where significant topographic relief occurs will require echo source discrimination to avoid the misinterpretation of surface echoes as arising from the subsurface. This can be accomplished through the identification of all Radar returns from the surface in order to positively identify subsurface echoes. We have developed general techniques for this using Airborne Radar data from the Dry Valleys of Antarctica. These data were collected in a single pass, including Taylor Glacier, ice-covered Lake Bonney, and an ice-free area of Taylor Valley. The pulsed Radar (52.5-67.5 MHz) was coherently recorded. Our echo discrimination techniques included a Radar simulator using a digital elevation model (DEM) to predict the location and shape of surface echoes in the Radar data. Real and simulated echo strengths were used to calculate a signal-to-clutter ratio. This was complemented by the cross-track migration of Radar echoes onto the surface. These migrated echoes were superimposed on the DEM and imagery in order to correlate with surface features. Using these techniques enabled us to identify a number of echoes in the Radar data as arising from the surface and to identify subsurface echoes, including a continuous reflector under the main trunk of Taylor Glacier and multiple reflectors beneath the terminus of Taylor Glacier. Surface-based Radar confirms the thickness of the glacier at three crossing points. The results illustrate the importance of using complementary techniques, the usefulness of a DEM, and the limitations of single-pass Radar sounding data.
M E Peters - One of the best experts on this subject based on the ideXlab platform.
-
along track focusing of Airborne Radar sounding data from west antarctica for improving basal reflection analysis and layer detection
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: M E Peters, D D Blankenship, S P Carter, Scott D Kempf, Duncan A Young, J W HoltAbstract:This paper presents focused synthetic aperture Radar (SAR) processing of Airborne Radar sounding data acquired with the High-Capability Radar Sounder system at 60 MHz. The motivation is to improve basal reflection analysis for water detection and to improve layer detection and tracking. The processing and reflection analyses are applied to data from Kamb Ice Stream, West Antarctica. The SAR processor correlates the Radar data with reference echoes from subsurface point targets. The references are 1-D responses limited by the pulse nadir footprint or 2-D responses that include echo tails. Unfocused SAR and incoherent integration are included for comparison. Echoes are accurately preserved from along-track slopes up to about 0.5deg for unfocused SAR, 3deg for 1-D correlations, and 10deg for 2-D correlations. The noise/clutter levels increase from unfocused SAR to 1-D and 2-D correlations, but additional gain compensates at the basal interface. The basal echo signal-to-noise ratio improvement is typically about 5 dB, and up to 10 dB for 2-D correlations in rough regions. The increased noise degrades the clarity of internal layers in the 2-D correlations, but detection of layers with slopes greater than 3deg is improved. Reflection coefficients are computed for basal water detection, and the results are compared for the different processing methods. There is a significant increase in the detected water from unfocused SAR to 1-D correlations, indicating that substantial basal water exists on moderately sloped interfaces. Very little additional water is detected from the 2-D correlations. The results from incoherent integration are close to the focused SAR results, but the noise/clutter levels are much greater.
-
along track focusing of Airborne Radar sounding data from west antarctica for improving basal reflection analysis and layer detection
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: M E Peters, D D Blankenship, S P Carter, Scott D Kempf, Duncan A Young, J W HoltAbstract:This paper presents focused synthetic aperture Radar (SAR) processing of Airborne Radar sounding data acquired with the High-Capability Radar Sounder system at 60 MHz. The motivation is to improve basal reflection analysis for water detection and to improve layer detection and tracking. The processing and reflection analyses are applied to data from Kamb Ice Stream, West Antarctica. The SAR processor correlates the Radar data with reference echoes from subsurface point targets. The references are 1-D responses limited by the pulse nadir footprint or 2-D responses that include echo tails. Unfocused SAR and incoherent integration are included for comparison. Echoes are accurately preserved from along-track slopes up to about 0.5deg for unfocused SAR, 3deg for 1-D correlations, and 10deg for 2-D correlations. The noise/clutter levels increase from unfocused SAR to 1-D and 2-D correlations, but additional gain compensates at the basal interface. The basal echo signal-to-noise ratio improvement is typically about 5 dB, and up to 10 dB for 2-D correlations in rough regions. The increased noise degrades the clarity of internal layers in the 2-D correlations, but detection of layers with slopes greater than 3deg is improved. Reflection coefficients are computed for basal water detection, and the results are compared for the different processing methods. There is a significant increase in the detected water from unfocused SAR to 1-D correlations, indicating that substantial basal water exists on moderately sloped interfaces. Very little additional water is detected from the 2-D correlations. The results from incoherent integration are close to the focused SAR results, but the noise/clutter levels are much greater.
-
echo source discrimination in single pass Airborne Radar sounding data from the dry valleys antarctica implications for orbital sounding of mars
Journal of Geophysical Research, 2006Co-Authors: J W Holt, M E Peters, Scott D Kempf, David L Morse, D D BlankenshipAbstract:The interpretation of Radar sounding data from Mars where significant topographic relief occurs will require echo source discrimination to avoid the misinterpretation of surface echoes as arising from the subsurface. This can be accomplished through the identification of all Radar returns from the surface in order to positively identify subsurface echoes. We have developed general techniques for this using Airborne Radar data from the Dry Valleys of Antarctica. These data were collected in a single pass, including Taylor Glacier, ice-covered Lake Bonney, and an ice-free area of Taylor Valley. The pulsed Radar (52.5-67.5 MHz) was coherently recorded. Our echo discrimination techniques included a Radar simulator using a digital elevation model (DEM) to predict the location and shape of surface echoes in the Radar data. Real and simulated echo strengths were used to calculate a signal-to-clutter ratio. This was complemented by the cross-track migration of Radar echoes onto the surface. These migrated echoes were superimposed on the DEM and imagery in order to correlate with surface features. Using these techniques enabled us to identify a number of echoes in the Radar data as arising from the surface and to identify subsurface echoes, including a continuous reflector under the main trunk of Taylor Glacier and multiple reflectors beneath the terminus of Taylor Glacier. Surface-based Radar confirms the thickness of the glacier at three crossing points. The results illustrate the importance of using complementary techniques, the usefulness of a DEM, and the limitations of single-pass Radar sounding data.
-
analysis techniques for coherent Airborne Radar sounding application to west antarctic ice streams
Journal of Geophysical Research, 2005Co-Authors: M E Peters, D D Blankenship, David L MorseAbstract:[1] Analysis of coherent Radar sounding echoes from polar ice sheets can provide information suitable for classifying the subglacial environment. Echoes from a general interface consist of both specularly reflected and diffusely scattered contributions. Specular reflection results from smooth uniform interfaces, whereas diffuse scattering results from rough nonuniform interfaces and inhomogeneous media. This article discusses how these phenomena are important to the acquisition and analysis of coherent Radar sounding data. Reflection results are presented from Airborne surveys conducted in 1987 over the downstream portions of Whillans Ice Stream and Ice Stream C, West Antarctica. Additionally, reflection and scattering analyses along with new results are presented for repeat profiles flown in 2001 over Ice Stream C. Analysis methods include using echo amplitudes to compute reflection coefficients which are used for inferring the dielectric properties of the subglacial material. Echo phase analysis provides the locations of dominant scattering centers which relate to reflection or scattering from the interface as well as provide interface roughness estimates. Comparison of low- and high-resolution imaging obtained from synthetic aperture Radar techniques indicates a reflecting and/or scattering interface. Combining the results from these independent analyses provides classification of the subglacial environment. Classified regions include smooth seawater, smooth saturated sediments, accreted marine ice, rough bottom crevasses, mixed conditions with partial subglacial water, and dry frozen conditions.
Zhaocheng Yang - One of the best experts on this subject based on the ideXlab platform.
-
space time adaptive processing for clutter suppression in coprime array and coprime pulse repetition interval Airborne Radar
International Symposium on Intelligent Signal Processing and Communication Systems, 2017Co-Authors: Xiaoye Wang, Zhaocheng Yang, Jianjun HuangAbstract:This paper develops two novel space-time adaptive processing (STAP) filters for clutter suppression in Airborne Radar with the coprime space-time sampling, which is realized by the coprime array and coprime pulse repetition interval (PRI). Different from the conventional STAP filters, the proposed STAP filters are derived by three steps. Firstly, a virtual space-time snapshot is constructed using the property of the coprime sampling. Secondly, an equivalent covariance matrix with enhanced degrees of freedom is computed by using spatial-temporal smoothing approach. Thirdly, two optimal STAP filters are derived based on the estimated covariance matrix. Simulations are conducted to validate the effectiveness of the proposed filters.
-
space time adaptive processing Airborne Radar with coprime pulse repetition interval
IEEE International Radar Conference, 2016Co-Authors: Zhaocheng Yang, Jingxiong Huang, Jianjun Huang, Li KangAbstract:In this paper, motivated by the success of coprime array in the direction-of-arrival (DOA) estimation, we introduce the idea of coprime pulse repetition interval (PRI) into the space-time adaptive processing (STAP) Airborne Radar. Through transmitting and receiving the pulses with coprime PRI, we can reduce the transmitting energy and improve the capabilities of electronic counter-countermeasures (ECCM). We use the lags between the receiving pulses to construct virtual pulses. By using the virtual pulses, we can obtain a new snapshot with a larger dimension than the real one. The constructed snapshots are exploited to estimate the clutter-plus-noise covariance matrix and then to form the STAP filter. Simulation results show that the proposed coprime PRI strategy STAP Radar can achieve a good performance with reduced pulses.
-
compressive space time adaptive processing Airborne Radar with random pulse repetition interval and random arrays
International Workshop on Compressed Sensing Theory and its Applications to Radar Sonar and Remote Sensing, 2016Co-Authors: Zhaocheng Yang, Guihua Quan, Jianjun HuangAbstract:This paper proposes a compressive space-time adaptive processing (CSTAP) Airborne Radar by reducing the samples in one coherence processing interval with random pulse repetition interval and random arrays, termed as the RPRI-RA Radar. We firstly detail the compressive sampling in spatial and Doppler domain and develop a rule for the clutter rank estimation for the RPRI-RA Radar. Then, CSTAP using the compressed samples without sparse reconstruction is proposed to mitigate the clutter. Additionally, from the point view of degrees of freedom, we perform a preliminary investigation about the configuration design for the target detection. Simulation results illustrate the effectiveness of above contents of the developed RPRI-RA Radar.
-
on clutter sparsity analysis in space time adaptive processing Airborne Radar
IEEE Geoscience and Remote Sensing Letters, 2013Co-Authors: Zhaocheng Yang, Hongqiang Wang, Weidong JiangAbstract:To have a further understanding of the recently developed space-time adaptive processing (STAP) methods based on sparse representation (SR-STAP), this letter details the clutter sparsity observed by STAP Radar systems. First, we review the principle and discuss the existing problems about clutter sparsity of the SR-STAP-type algorithms. Then, a theoretical analysis on clutter sparsity for a side-looking uniform linear array with constant pulse repetition frequency, constant velocity, and no crab is performed. Some important conclusions are obtained, and simulations are used to validate the correctness of them.
-
l_1 regularized stap algorithms with a generalized sidelobe canceler architecture for Airborne Radar
IEEE Transactions on Signal Processing, 2012Co-Authors: Zhaocheng Yang, Rodrigo C De LamareAbstract:In this paper, we propose novel l1-regularized space-time adaptive processing (STAP) algorithms with a generalized sidelobe canceler architecture for Airborne Radar applications. The proposed methods suppose that a number of samples at the output of the blocking process are not needed for sidelobe canceling, which leads to the sparsity of the STAP filter weight vector. The core idea is to impose a sparse regularization (l1-norm type) to the minimum variance criterion. By solving this optimization problem, an l1-regularized recursive least squares (l1-based RLS) adaptive algorithm is developed. We also discuss the SINR steady-state performance and the penalty parameter setting of the proposed algorithm. To adaptively set the penalty parameter, two switched schemes are proposed for l1-based RLS algorithms. The computational complexity analysis shows that the proposed algorithms have the same complexity level as the conventional RLS algorithm (O((NM)2)), where NM is the filter weight vector length), but a significantly lower complexity level than the loaded sample covariance matrix inversion algorithm (O((NM)3)) and the compressive sensing STAP algorithm (O((NsNd)3), where N8Nd >; NM is the angle-Doppler plane size). The simulation results show that the proposed STAP algorithms converge rapidly and provide a SINR improvement using a small number of snapshots.
D D Blankenship - One of the best experts on this subject based on the ideXlab platform.
-
along track focusing of Airborne Radar sounding data from west antarctica for improving basal reflection analysis and layer detection
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: M E Peters, D D Blankenship, S P Carter, Scott D Kempf, Duncan A Young, J W HoltAbstract:This paper presents focused synthetic aperture Radar (SAR) processing of Airborne Radar sounding data acquired with the High-Capability Radar Sounder system at 60 MHz. The motivation is to improve basal reflection analysis for water detection and to improve layer detection and tracking. The processing and reflection analyses are applied to data from Kamb Ice Stream, West Antarctica. The SAR processor correlates the Radar data with reference echoes from subsurface point targets. The references are 1-D responses limited by the pulse nadir footprint or 2-D responses that include echo tails. Unfocused SAR and incoherent integration are included for comparison. Echoes are accurately preserved from along-track slopes up to about 0.5deg for unfocused SAR, 3deg for 1-D correlations, and 10deg for 2-D correlations. The noise/clutter levels increase from unfocused SAR to 1-D and 2-D correlations, but additional gain compensates at the basal interface. The basal echo signal-to-noise ratio improvement is typically about 5 dB, and up to 10 dB for 2-D correlations in rough regions. The increased noise degrades the clarity of internal layers in the 2-D correlations, but detection of layers with slopes greater than 3deg is improved. Reflection coefficients are computed for basal water detection, and the results are compared for the different processing methods. There is a significant increase in the detected water from unfocused SAR to 1-D correlations, indicating that substantial basal water exists on moderately sloped interfaces. Very little additional water is detected from the 2-D correlations. The results from incoherent integration are close to the focused SAR results, but the noise/clutter levels are much greater.
-
along track focusing of Airborne Radar sounding data from west antarctica for improving basal reflection analysis and layer detection
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: M E Peters, D D Blankenship, S P Carter, Scott D Kempf, Duncan A Young, J W HoltAbstract:This paper presents focused synthetic aperture Radar (SAR) processing of Airborne Radar sounding data acquired with the High-Capability Radar Sounder system at 60 MHz. The motivation is to improve basal reflection analysis for water detection and to improve layer detection and tracking. The processing and reflection analyses are applied to data from Kamb Ice Stream, West Antarctica. The SAR processor correlates the Radar data with reference echoes from subsurface point targets. The references are 1-D responses limited by the pulse nadir footprint or 2-D responses that include echo tails. Unfocused SAR and incoherent integration are included for comparison. Echoes are accurately preserved from along-track slopes up to about 0.5deg for unfocused SAR, 3deg for 1-D correlations, and 10deg for 2-D correlations. The noise/clutter levels increase from unfocused SAR to 1-D and 2-D correlations, but additional gain compensates at the basal interface. The basal echo signal-to-noise ratio improvement is typically about 5 dB, and up to 10 dB for 2-D correlations in rough regions. The increased noise degrades the clarity of internal layers in the 2-D correlations, but detection of layers with slopes greater than 3deg is improved. Reflection coefficients are computed for basal water detection, and the results are compared for the different processing methods. There is a significant increase in the detected water from unfocused SAR to 1-D correlations, indicating that substantial basal water exists on moderately sloped interfaces. Very little additional water is detected from the 2-D correlations. The results from incoherent integration are close to the focused SAR results, but the noise/clutter levels are much greater.
-
echo source discrimination in single pass Airborne Radar sounding data from the dry valleys antarctica implications for orbital sounding of mars
Journal of Geophysical Research, 2006Co-Authors: J W Holt, M E Peters, Scott D Kempf, David L Morse, D D BlankenshipAbstract:The interpretation of Radar sounding data from Mars where significant topographic relief occurs will require echo source discrimination to avoid the misinterpretation of surface echoes as arising from the subsurface. This can be accomplished through the identification of all Radar returns from the surface in order to positively identify subsurface echoes. We have developed general techniques for this using Airborne Radar data from the Dry Valleys of Antarctica. These data were collected in a single pass, including Taylor Glacier, ice-covered Lake Bonney, and an ice-free area of Taylor Valley. The pulsed Radar (52.5-67.5 MHz) was coherently recorded. Our echo discrimination techniques included a Radar simulator using a digital elevation model (DEM) to predict the location and shape of surface echoes in the Radar data. Real and simulated echo strengths were used to calculate a signal-to-clutter ratio. This was complemented by the cross-track migration of Radar echoes onto the surface. These migrated echoes were superimposed on the DEM and imagery in order to correlate with surface features. Using these techniques enabled us to identify a number of echoes in the Radar data as arising from the surface and to identify subsurface echoes, including a continuous reflector under the main trunk of Taylor Glacier and multiple reflectors beneath the terminus of Taylor Glacier. Surface-based Radar confirms the thickness of the glacier at three crossing points. The results illustrate the importance of using complementary techniques, the usefulness of a DEM, and the limitations of single-pass Radar sounding data.
-
analysis techniques for coherent Airborne Radar sounding application to west antarctic ice streams
Journal of Geophysical Research, 2005Co-Authors: M E Peters, D D Blankenship, David L MorseAbstract:[1] Analysis of coherent Radar sounding echoes from polar ice sheets can provide information suitable for classifying the subglacial environment. Echoes from a general interface consist of both specularly reflected and diffusely scattered contributions. Specular reflection results from smooth uniform interfaces, whereas diffuse scattering results from rough nonuniform interfaces and inhomogeneous media. This article discusses how these phenomena are important to the acquisition and analysis of coherent Radar sounding data. Reflection results are presented from Airborne surveys conducted in 1987 over the downstream portions of Whillans Ice Stream and Ice Stream C, West Antarctica. Additionally, reflection and scattering analyses along with new results are presented for repeat profiles flown in 2001 over Ice Stream C. Analysis methods include using echo amplitudes to compute reflection coefficients which are used for inferring the dielectric properties of the subglacial material. Echo phase analysis provides the locations of dominant scattering centers which relate to reflection or scattering from the interface as well as provide interface roughness estimates. Comparison of low- and high-resolution imaging obtained from synthetic aperture Radar techniques indicates a reflecting and/or scattering interface. Combining the results from these independent analyses provides classification of the subglacial environment. Classified regions include smooth seawater, smooth saturated sediments, accreted marine ice, rough bottom crevasses, mixed conditions with partial subglacial water, and dry frozen conditions.
Scott D Kempf - One of the best experts on this subject based on the ideXlab platform.
-
along track focusing of Airborne Radar sounding data from west antarctica for improving basal reflection analysis and layer detection
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: M E Peters, D D Blankenship, S P Carter, Scott D Kempf, Duncan A Young, J W HoltAbstract:This paper presents focused synthetic aperture Radar (SAR) processing of Airborne Radar sounding data acquired with the High-Capability Radar Sounder system at 60 MHz. The motivation is to improve basal reflection analysis for water detection and to improve layer detection and tracking. The processing and reflection analyses are applied to data from Kamb Ice Stream, West Antarctica. The SAR processor correlates the Radar data with reference echoes from subsurface point targets. The references are 1-D responses limited by the pulse nadir footprint or 2-D responses that include echo tails. Unfocused SAR and incoherent integration are included for comparison. Echoes are accurately preserved from along-track slopes up to about 0.5deg for unfocused SAR, 3deg for 1-D correlations, and 10deg for 2-D correlations. The noise/clutter levels increase from unfocused SAR to 1-D and 2-D correlations, but additional gain compensates at the basal interface. The basal echo signal-to-noise ratio improvement is typically about 5 dB, and up to 10 dB for 2-D correlations in rough regions. The increased noise degrades the clarity of internal layers in the 2-D correlations, but detection of layers with slopes greater than 3deg is improved. Reflection coefficients are computed for basal water detection, and the results are compared for the different processing methods. There is a significant increase in the detected water from unfocused SAR to 1-D correlations, indicating that substantial basal water exists on moderately sloped interfaces. Very little additional water is detected from the 2-D correlations. The results from incoherent integration are close to the focused SAR results, but the noise/clutter levels are much greater.
-
along track focusing of Airborne Radar sounding data from west antarctica for improving basal reflection analysis and layer detection
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: M E Peters, D D Blankenship, S P Carter, Scott D Kempf, Duncan A Young, J W HoltAbstract:This paper presents focused synthetic aperture Radar (SAR) processing of Airborne Radar sounding data acquired with the High-Capability Radar Sounder system at 60 MHz. The motivation is to improve basal reflection analysis for water detection and to improve layer detection and tracking. The processing and reflection analyses are applied to data from Kamb Ice Stream, West Antarctica. The SAR processor correlates the Radar data with reference echoes from subsurface point targets. The references are 1-D responses limited by the pulse nadir footprint or 2-D responses that include echo tails. Unfocused SAR and incoherent integration are included for comparison. Echoes are accurately preserved from along-track slopes up to about 0.5deg for unfocused SAR, 3deg for 1-D correlations, and 10deg for 2-D correlations. The noise/clutter levels increase from unfocused SAR to 1-D and 2-D correlations, but additional gain compensates at the basal interface. The basal echo signal-to-noise ratio improvement is typically about 5 dB, and up to 10 dB for 2-D correlations in rough regions. The increased noise degrades the clarity of internal layers in the 2-D correlations, but detection of layers with slopes greater than 3deg is improved. Reflection coefficients are computed for basal water detection, and the results are compared for the different processing methods. There is a significant increase in the detected water from unfocused SAR to 1-D correlations, indicating that substantial basal water exists on moderately sloped interfaces. Very little additional water is detected from the 2-D correlations. The results from incoherent integration are close to the focused SAR results, but the noise/clutter levels are much greater.
-
echo source discrimination in single pass Airborne Radar sounding data from the dry valleys antarctica implications for orbital sounding of mars
Journal of Geophysical Research, 2006Co-Authors: J W Holt, M E Peters, Scott D Kempf, David L Morse, D D BlankenshipAbstract:The interpretation of Radar sounding data from Mars where significant topographic relief occurs will require echo source discrimination to avoid the misinterpretation of surface echoes as arising from the subsurface. This can be accomplished through the identification of all Radar returns from the surface in order to positively identify subsurface echoes. We have developed general techniques for this using Airborne Radar data from the Dry Valleys of Antarctica. These data were collected in a single pass, including Taylor Glacier, ice-covered Lake Bonney, and an ice-free area of Taylor Valley. The pulsed Radar (52.5-67.5 MHz) was coherently recorded. Our echo discrimination techniques included a Radar simulator using a digital elevation model (DEM) to predict the location and shape of surface echoes in the Radar data. Real and simulated echo strengths were used to calculate a signal-to-clutter ratio. This was complemented by the cross-track migration of Radar echoes onto the surface. These migrated echoes were superimposed on the DEM and imagery in order to correlate with surface features. Using these techniques enabled us to identify a number of echoes in the Radar data as arising from the surface and to identify subsurface echoes, including a continuous reflector under the main trunk of Taylor Glacier and multiple reflectors beneath the terminus of Taylor Glacier. Surface-based Radar confirms the thickness of the glacier at three crossing points. The results illustrate the importance of using complementary techniques, the usefulness of a DEM, and the limitations of single-pass Radar sounding data.
