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ABSTRACT: Tandem-L is a mission proposal for an innovative interferometric L-band radar instrument that enables the systematic monitoring of dynamic Earth processes using advanced techniques and technologies. The mission is science driven aiming to provide a unique data set for climate and environmental research, geodynamics, hydrology and oceanography. Important application examples are global forest height and biomass inventories, measurements of Earth deformation due to tectonic processes and/or anthropogenic factors, observations of ice/glacier velocity field and 3-D structure changes, and the monitoring of soil moisture and ocean surface currents. The Tandem-L mission concept consists of two cooperating satellites flying in close formation. The Pol-InSAR and repeat-pass acquisition modes provide a unique data source to observe, analyse and quantify a wide range of mutually interacting processes in the bio-, litho-, hydroand cryosphere. The systematic observation of these processes benefits from the high data acquisition capacity and the novel high-resolution wide-swath SAR imaging modes that combine digital beamforming with a large reflector antenna. This paper provides an overview of the Tandem-L mission concept and its main application areas. It is planned to realise the Tandem-L mission in cooperation with NASA/JPL. The mission concept was developed in detail in a joint two-year pre-phase A study and it will be further studied in the next 18 months. This will allow a cost-effective implementation, whereby each partner contributes its predevelopments and experience. According to current planning, the Tandem-L satellites could be launched in 2019.
Geoscience and Remote Sensing Symposium (IGARSS), 2011 IEEE International; 08/2011
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ABSTRACT: In recent years, there has been increased interest in using synthetic aperture radar (SAR) to study and monitor glaciers and ice sheets for glaciological and climate change research. However, due to the medium's complexity, SAR backscattering from ice remains poorly understood, including the relative importance of scattering from surface and volume layers and also dependences on frequency and glacier zone. Extreme weather conditions can result in quickly changing surface conditions influencing backscatter signatures while leaving the underlying volume of interest unchanged. Surface and volume components must thus be separated in order to infer information regarding the properties of the ice volume. This paper describes a three-component scattering model to decompose polarimetric SAR (PolSAR) images of glacier ice. Total backscatter is modeled as the incoherent summation of surface, volume, and sastrugi (wind-induced feature) components. The proposed model adapts and extends the Freeman and Durden decomposition for an ice volume scenario in which the volume is a dielectric medium. Forms of the model for both random and oriented volumes are considered, and a new oriented sastrugi component is introduced which is able to explain backscatter behavior between different winter scenes. Validation is performed with airborne PolSAR data at L- and P-band collected using the E-SAR system of the German Aerospace Center over the Austfonna ice cap in Svalbard, Norway, as part of the ICESAR campaign.
IEEE Transactions on Geoscience and Remote Sensing 02/2011; · 2.89 Impact Factor
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G. Krieger,
I. Hajnsek,
K. Papathanassiou,
M. Eineder,
M. Younis,
F. De Zan,
S. Huber,
P. Lopez-Dekker,
P. Prats,
M. Werner,
Y. Shen,
A. Freeman,
P. Rosen,
S. Hensley,
W. Johnson,
L. Veilleux,
B. Grafmueller,
R. Werninghaus,
R. Bamler, A. Moreira
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ABSTRACT: Tandem-L is a proposal for an innovative interferometric and polarimetric radar mission that enables the systematic monitoring of dynamic processes on the Earth surface. Important mission objectives are global forest height and biomass inventories, large scale measurements of millimetric displacements due to tectonic shifts, and systematic observations of glacier movements. The innovative mission concept and the high data acquisition capacity of Tandem-L provide a unique data source to observe, analyze and quantify the dynamics of a wide range of mutually interacting processes in the bio-, litho-, hydro- and cryosphere. By this, Tandem-L will be an essential step to advance our understanding of the Earth system and its intricate dynamics.
Geoscience and Remote Sensing Symposium (IGARSS), 2010 IEEE International; 08/2010
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ABSTRACT: The success of current spaceborne Synthetic Aperture Radar (SAR) is boosting the performance requirement of next generation systems. In order to cope with the evolution of SAR the design of the new systems will need to meet higher requirements for spatial and radiometric resolution together with an increased availability. This tendency is recognized nearly independently of the application area and manifests itself through several study programs initiated by space agencies aiming at the design of future SAR systems. In this context the use of large reflectors combined with digital feed arrays for SAR is considered a possible alternative to planar array antennas. This paper suggests an X-band spaceborne SAR system utilizing a deployable reflector together with a digital feed array, analyzes its performance and highlights its advantages compared to other systems based on direct radiating arrays.
Geoscience and Remote Sensing Symposium (IGARSS), 2010 IEEE International; 08/2010
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T. Borner,
F. De Zan,
P. Lopez-Dekker,
G. Krieger,
I. Hajnsek,
K. Papathanassiou,
M. Villano,
M. Younis,
A. Danklmayer,
W. Dierking,
T. Nagler,
H. Rott,
S. Lehner,
T. Fugen, A. Moreira
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ABSTRACT: SIGNAL is an innovative earth exploration mission proposal with the main objective to estimate accurately and repeatedly topography and topographic changes associated with mass change or other dynamic effects on glaciers, ice caps and polar ice sheets. Elevation measurements are complemented with glacier velocity measurements, providing valuable additional information for a better understanding of the hydrology of glacierized basins and of the Arctic and Antarctic water cycle. SIGNAL is capable of monitoring all critical regions with a high spatial resolution and an adequate revisit time. This paper gives an overview about the actual mission design status and provides a brief description of the topography (DEM - digital elevation map) self-calibration strategy and the estimated global interferometric performance.
Geoscience and Remote Sensing Symposium (IGARSS), 2010 IEEE International; 08/2010
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ABSTRACT: This paper reviews advanced multi-channel SAR system concepts for the imaging of wide swaths with high resolution. Several novel system architectures employing both direct radiating arrays and reflector antennas fed by a digital array are introduced and compared to each other with regard to their imaging performance. In addition, innovative SAR imaging modes are proposed which enable the mapping of ultra-wide swaths with high azimuth resolution. The new techniques and technologies have the potential to enhance the imaging performance of future SAR systems by one order of magnitude if compared to state of the art SAR sensors like TerraSAR-X, ALOS, Radarsat-2 or Sentinel-1.
Geoscience and Remote Sensing Symposium (IGARSS), 2010 IEEE International; 08/2010
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ABSTRACT: Due to a system-inherent limitation, conventional synthetic aperture radar (SAR) is incapable of imaging a wide swath with high geometric resolution. This restriction can be overcome by systems with multiple receive channels in combination with an additional digital signal processing network. So far, the application of such digital beamforming algorithms for high-resolution wide-swath SAR imaging has been restricted to multichannel systems in stripmap operation. However, in stripmap mode, the overall azimuth antenna length restricts the achievable swath width, thus preventing very wide swaths as requested by future SAR missions. Consequently, new concepts for ultrawide-swath imaging are needed. A promising candidate is a SAR system with multiple azimuth channels being operated in burst mode. This paper analyzes innovative ScanSAR and Terrain Observation by Progressive Scans (TOPS) system concepts with regard to multichannel azimuth processing. For this, the theoretical analyses, performance figures, and SAR signal processing, which had previously been derived for multichannel stripmap mode, are extended to systems operating in burst modes. The investigations reveal that multichannel ScanSAR systems enable the imaging of ultrawide swaths with high azimuth resolution and compact antenna lengths. These considerations are embedded in a multichannel ScanSAR system design example to demonstrate its capability to image an ultrawide swath of 400 km with a high geometric resolution of 5 m. In a next step, this system is adapted to TOPS mode operation, including an innovative “staircase” multichannel processing approach optimized for TOPS.
IEEE Transactions on Geoscience and Remote Sensing 08/2010; · 2.89 Impact Factor
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ABSTRACT: This paper reviews advanced multi-channel SAR system concepts for the imaging of wide swaths with high resolution. Several novel system architectures employing both direct radiating arrays and reflector antennas fed by a digital array are introduced and compared to each other with regard to their imaging performance. In addition, innovative SAR imaging modes are proposed which enable the mapping of ultra-wide swaths with high azimuth resolution. The new techniques and technologies have the potential to enhance the imaging performance of future SAR systems by one order of magnitude if compared to state of the art SAR sensors like TerraSAR-X, ALOS, Radarsat-2 or Sentinel-1.
Synthetic Aperture Radar (EUSAR), 2010 8th European Conference on; 07/2010
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G. Krieger,
I. Hajnsek,
K. Papathanassiou,
M. Eineder,
M. Younis,
F. De Zan,
P. Lopez-Dekker,
S. Huber,
M. Werner,
P. Prats,
H. Fiedler,
A. Freeman,
P. Rosen,
S. Hensley,
W. Johnson,
L. Veilleux,
B. Grafmueller,
R. Werninghaus,
R. Bamler, A Moreira
[show abstract]
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ABSTRACT: Tandem-L is a proposal for an innovative interferometric and polarimetric radar mission that enables the systematic monitoring of dynamic processes on the Earth surface. Important mission objectives are global forest height and biomass inventories, large scale measurements of millimetric displacements due to tectonic shifts, and systematic observations of glacier movements. The irmovative mission concept and the high data acquisition capacity of Tandem-L provide a unique data source to observe, analyze and quantity the dynamics of a wide range of mutually interacting processes in the bio-, litho-, hydro- and cryosphere. By this, Tandem-L will be an essential step to advance our understanding of the Earth system and its intricate dynamics.
Synthetic Aperture Radar (EUSAR), 2010 8th European Conference on; 07/2010
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ABSTRACT: This paper presents an overview of single-pass interferometric Synthetic Aperture Radar (SAR) missions employing two or more satellites flying in a close formation. The simultaneous reception of the scattered radar echoes from different viewing directions by multiple spatially distributed antennas enables the acquisition of unique Earth observation products for environmental and climate monitoring. After a short introduction to the basic principles and applications of SAR interferometry, designs for the twin satellite missions TanDEM-X and Tandem-L are presented. The primary objective of TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is the generation of a global Digital Elevation Model (DEM) with unprecedented accuracy as the basis for a wide range of scientific research as well as for commercial DEM production. This goal is achieved by enhancing the TerraSAR-X mission with a second TerraSAR-X like satellite that will be launched in spring 2010. Both satellites act then as a large single-pass SAR interferometer with the opportunity for flexible baseline selection. Building upon the experience gathered with the TanDEM-X mission design, the fully polarimetric L-band twin satellite formation Tandem-L is proposed. Important objectives of this highly capable interferometric SAR mission are the global acquisition of three-dimensional forest structure and biomass inventories, large-scale measurements of millimetric displacements due to tectonic shifts, and systematic observations of glacier movements. The sophisticated mission concept and the high data-acquisition capacity of Tandem-L will moreover provide a unique data source to systematically observe, analyze, and quantify the dynamics of a wide range of additional processes in the bio-, litho-, hydro-, and cryosphere. By this, Tandem-L will be an essential step to advance our understanding of the Earth system and its intricate dynamics. Enabling technologies and techniques are described in detail. An ou-
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tlook on future interferometric and tomographic concepts and developments, including multistatic SAR systems with multiple receivers, is provided.
Proceedings of the IEEE 06/2010; · 6.81 Impact Factor
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ABSTRACT: We report about the first X-band spaceborne-airborne bistatic synthetic aperture radar (SAR) experiment, conducted early November 2007, using the German satellite TerraSAR-X as transmitter and the German Aerospace Center's (DLR) new airborne radar system F-SAR as receiver. The importance of the experiment resides in both its pioneering character and its potential to serve as a test bed for the validation of nonstationary bistatic acquisitions, novel calibration and synchronization algorithms, and advanced imaging techniques. Due to the independent operation of the transmitter and receiver, an accurate synchronization procedure was needed during processing to make high-resolution imaging feasible. Precise phase-preserving bistatic focusing can only be achieved if time and phase synchronization exist. The synchronization approach, based on the evaluation of the range histories of several reference targets, was verified through a separate analysis of the range and Doppler contributions. After successful synchronization, nonstationary focusing was performed using a bistatic backprojection algorithm. During the campaign, stand-alone TerraSAR-X monostatic as well as interoperated TerraSAR-X/F-SAR bistatic data sets were recorded. As expected, the bistatic image shows a space-variant behavior in spatial resolution and in signal-to-noise ratio. Due to the selected configuration, the bistatic image outperforms its monostatic counterpart in almost the complete imaged scene. A detailed comparison between monostatic and bistatic images is given, illustrating the complementarity of both measurements in terms of backscatter and Doppler information. The results are of fundamental importance for the development of future nonsynchronized bistatic SAR systems.
IEEE Transactions on Geoscience and Remote Sensing 03/2010; · 2.89 Impact Factor
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ABSTRACT: The 34 papers in this special issue provide an overview of the TerraSAR-X mission, commissioning phase, calibration, data processing, and applications.
IEEE Transactions on Geoscience and Remote Sensing 03/2010; · 2.89 Impact Factor
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ABSTRACT: This paper presents an efficient phase preserving processor for the focusing of data acquired in sliding spotlight and Terrain Observation by Progressive Scans (TOPS) imaging modes. They share in common a linear variation of the Doppler centroid along the azimuth dimension, which is due to a steering of the antenna (either mechanically or electronically) throughout the data take. Existing approaches for the azimuth processing can become inefficient due to the additional processing to overcome the folding in the focused domain. In this paper, a new azimuth scaling approach is presented to perform the azimuth processing, whose kernel is exactly the same for sliding spotlight and TOPS modes. The possibility to use the proposed approach to process data acquired in the ScanSAR mode, as well as a discussion concerning staring spotlight, is also included. Simulations with point targets and real data acquired by TerraSAR-X in sliding spotlight and TOPS modes are used to validate the developed algorithm.
IEEE Transactions on Geoscience and Remote Sensing 03/2010; · 2.89 Impact Factor
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ABSTRACT: This paper presents an efficient phase preserving processor for the focusing of data acquired in sliding spotlight, TOPS (Terrain Observation by Progressive Scans) and ScanSAR imaging modes. They share in common a linear variation of the Doppler centroid along the azimuth dimension, which is due to a steering of the antenna (either mechanically or electronically) throughout the data take for the first two modes, and due to the burst mode in the ScanSAR case. Existing approaches for the azimuth processing can become inefficient due to the additional processing to overcome the folding in the focused domain. In this paper an azimuth scaling approach is presented to perform the azimuth processing, whose kernel is the same for all three modes. Data acquired by TerraSAR-X in sliding spotlight, TOPS and ScanSAR modes are used to validate the developed algorithm.
Geoscience and Remote Sensing Symposium,2009 IEEE International,IGARSS 2009; 08/2009
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E. Pottier,
L. Ferro-Famil,
S. Allain,
S. Cloude,
I. Hajnsek,
K. Papathanassiou, A. Moreira,
M. Williams,
A. Minchella,
M. Lavalle,
Y.-L. Desnos
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ABSTRACT: The objective of this paper is to make a review of the current status of the PolSARpro v4.0 Software (Polarimetric SAR Data Processing and Educational Toolbox), developed under contract to ESA by a consortium comprising I.E.T.R at the University of Rennes 1, AELc, DLR-HR and Dr mark Williams from Adelaide. The objective of this current project is to provide Educational Software that offers a tool for self-education in the field of Polarimetric SAR data analysis at University level and a comprehensive suite of functions for the scientific exploitation of fully and partially polarimetric multi-data sets and the development of applications for such data. The PolSARpro v4.0 Software establishes a foundation for the exploitation of Polarimetric techniques for scientific developments and stimulates research and applications developments using PolSAR and PolInSAR data.
Geoscience and Remote Sensing Symposium,2009 IEEE International,IGARSS 2009; 08/2009
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ABSTRACT: This paper presents the very first assessment of the permanent scatterer (PS) technique for airborne data. A data set of 14 SAR images at L-band, acquired over the Oberpfaffenhofen area on the same day with the E-SAR system of the German Aerospace Center (DLR), is used for the first airborne time series analysis with PS. The paper shows the importance of mitigating the residual motion errors through the use of precise motion compensation strategy before PS analysis. The target velocity and DEM error results are obtained by a periodogram-based estimation considering the linear displacement model. Due to the small number of images in our data set, the displacement velocity and DEM error results are presented on a PS basis. Target structures related to selected reliable PSs are shown and the corresponding periodograms highlighted.
Geoscience and Remote Sensing Symposium,2009 IEEE International,IGARSS 2009; 08/2009
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ABSTRACT: Following the success of the first bistatic spaceborne-airborne experiment between TerraSAR-X and F-SAR carried out in November 2007, DLR has performed a second bistatic experiment in July 2008 with new challenging acquisitions. Furthermore, the existing bistatic processing chain has been updated with two significant improvements: a) clock offset synchronisation is now performed without the use of reference targets, and b) SAR imaging is done using a fast focussing technique. The new SAR imaging algorithm, based on the fast factorised backprojection algorithm, has proved very good focussing qualities while dramatically reducing (up to a factor 100 with respect to direct backprojection) the overall computational load. The new processing chain is tested using the image of the first TerraSAR-X experiment. Results of a dualpol acquisition performed during the second TerraSAR-X/F-SAR experiment and showing the first dual-pol bistatic spaceborne-airborne images are also presented in this paper.
Geoscience and Remote Sensing Symposium,2009 IEEE International,IGARSS 2009; 08/2009
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G. Krieger,
I. Hajnsek,
K. Papathanassiou,
M. Eineder,
M. Younis,
F. De Zan,
P. Prats,
S. Huber,
M. Werner,
H. Fiedler,
A. Freeman,
P. Rosen,
S. Hensley,
W. Johnson,
L. Veilleux,
B. Grafmueller,
R. Werninghaus,
R. Bamler, A. Moreira
[show abstract]
[hide abstract]
ABSTRACT: Tandem-L is a proposal for an innovative interferometric and polarimetric radar mission that enables the systematic monitoring of dynamic processes on the Earth surface. Important mission objectives are global forest height and biomass inventories, large scale measurements of millimetric displacements due to tectonic shifts, and systematic observations of glacier movements. The innovative mission concept and the high data acquisition capacity of Tandem-L provide a unique data source to observe, analyze and quantify the dynamics of a wide range of mutually interacting processes in the bio-, litho-, hydro- and cryosphere. By this, Tandem-L will be an essential step to advance our understanding of the Earth system and its intricate dynamics. This paper provides an overview of the Tandem-L mission concept and its main application areas. Performance predictions show the great potential of Tandem-L to acquire a wide range of bio- and geophysical parameters with high accuracy on a global scale. Innovative aspects like the employment of advanced digital beamforming techniques to improve performance and coverage are discussed in detail.
Radar Conference, 2009 IEEE; 06/2009
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G. Krieger,
M. Zink,
H. Fiedler,
I. Hajnsek,
M. Younis,
S. Huber,
M. Bachmann,
J.H. Gonzalez,
D. Schulze,
J. Boer,
M. Werner, A. Moreira
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ABSTRACT: TanDEM-X (TerraSAR-X add-on for digital elevation measurements) is an innovative spaceborne radar interferometer mission that will be launched in autumn 2009. This paper gives an overview of the TanDEM-X mission concept, summarizes the basic products, illustrates the achievable performance, and provides some examples for new imaging modes and applications.
Radar Conference, 2009 IEEE; 06/2009
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ABSTRACT: We have seen in the above that the SweepSAR technique offers the potential for significant reductions in the transmit peak and average power required for a SAR system. This is achieved by making full use of the areal extent of a reflector antenna on receive. The SweepSAR rate is not as big a problem as it might appear initially: note that in the 30 years since Seasat launched downlink rates for LEO satellites have increased significantly - from ~85 Mbps up to ~640 Mbps. In addition, analog-to digital converters (ADCs) have increased in bandwidth from ~ 20 MHz to several GHz. In this paper, an alternative approach is described that is suited for longer wavelength SARs in particular, employing a large, deployable reflector antenna and a much simpler phased array feed. To illuminate a wide swath, a substantial fraction of the phased array feed is excited on transmit to sub-illuminate the reflector. Shorter transmit pulses are required than for conventional SAR. On receive, a much smaller portion of the phased array feed is used to collect the return echo, so that a greater portion of the reflector antenna area is used. The locus of the portion of the phased array used on receive is adjusted using an analog beam steering network, to 'sweep' the receive beam(s) across the illuminated swath, tracking the return echo. This is similar in some respects to the whiskbroom approach to optical sensors, hence the name: SweepSAR. SweepSAR has advantages over conventional SAR in that it requires less transmit power, and if the receive beam is narrow enough, it is relatively immune to range ambiguities. Compared to direct radiating arrays with digital beam-forming, it is much simpler to implement, uses currently available technologies, is better suited for longer wavelength systems, and does not require extremely high data rates or onboard processing.
Radar Conference, 2009 IEEE; 06/2009
