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Institute Seminar - Presentations 2013

Anton Patyuchenko "Advanced Antenna Concepts for Multi-Modal Radar Systems"

Dienstag, 17. September 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Coming soon.

Rafaela Lopes Melo "Hardware Extension and Experiments for the Digital Beamforming Radar Ground "

Dienstag, 16. Juli 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Coming soon.

Jan Eilers "Systemtechnik Simulation Framework"

Dienstag, 09. Juli 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
The Systemtechnik Simulation Framework (S-SF) is a software suit, which contains an analysis tool set. The idea behind the S-SF is to describe one space related scenario and do the analysis in one environment. This is to avoid failures by using different software modules to analyze a scenario and to increase the speed of a study. The scenario contains definitions of different objects (targets, ground stations, satellites, sensors, subsystems, image products,…). For the celestial calculations like a satellite orbit, contact times or angles it is possible to choose between two engines. One is AGI-STK the other is VENI. AGI-STK is commercial software to model, analyze and visualize space, defense and intelligence systems with an interface for different program languages. VENI is in-house developed software to model and analyze space systems. A small subset from this toolbox is the mission analysis, mission planning and interferometry analysis for satellite constellations.

Werner Wiesbeck "Systemkonzepte für das Radar 2020"

Freitag, 05. Juli 2013
10.30 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Die Radartechnik ist inzwischen fast 110 Jahre für die unterschiedlichsten Aufgaben und Anwendungen eingesetzt worden. In dieser Zeit hat sich die Systemtechnik des Radars den Innovationszyklen der Technologie und des Bedarfs angepasst. Typische Beispiele waren das Pulsradar oder Phased Array, um nur zwei zu nennen. In den nächsten Jahren ist ein nahe zu revolutionärer Technologiesprung in der Radartechnik zu erwarten. Die erforderlichen und sich geradezu aufdrängenden Technologien resultieren weitgehend aus der Kommunikationstechnik. Sie werden in die Radarsystemtechnik einfließen und vollkommen neue Möglichkeiten eröffnen. Im Einzelnen sind die zu erwartenden Systemideen: - Intelligente Signalcodierung - MIMO Radar - Digitale Strahlformung - Array Imaging - Kombination Radar x Kommunikation = RadCom In dem Vortrag werden diese neuen Technologien von der Systemseite betrachtet und integriert. Durch diese neuen Systemtechnologien werden die Radare leistungsfähiger, flexibler und auch kostengünstiger werden. Ihre mögliche Anwendung erstreckt sich auf nahezu alle Bereiche der Radartechnik und erschließt zudem neue Anwendungen.

Michele Martone "Decorrelation Effects in Bistatic TanDEM-X Acquisitions"

Dienstag, 25. Juni 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Coming soon.

Harald Anglberger "The usage of SAR simulation for practical applications"

Dienstag, 18. Juni 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
In the past few years a SAR simulator called SAREF has been developed in the institute mainly for the design of future high resolution SAR systems and for the analysis of existing ones. This end-to-end simulation chain makes it possible to study the impact on image quality by a variation of system parameters not only on point scatterers, but also on complex objects or small scenes. Initially, SAREF was specifically designed as a toolset for the expert radar scientist. Recently, the simulator has been made applicable for the actual user of SAR remote sensing data. This presentation will illustrate the major achievements by giving application examples for the simulator in the fields of signature analysis, user assisted object recognition, image acquisition planning and merging of optical and SAR data in the radar slant-range space.

Timo Kempf "title coming soon"

Dienstag, 04. Juni 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Coming soon.

Paola Rizzoli "Radar Backscatter Modelling with TanDEM-X Data"

Dienstag, 14. Mai 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Radar backscatter knowledge represents a valuable input for many remote sensing applications. The amount of data acquired within the TanDEM-X mission allows for the characterization of X-band backscatter on a global scale. A method for the characterization of radar backscatter behavior using a global statistical approach will be presented. A series of models can be derived, focusing on the backscatter dependency on polarization, local incidence angle, ground classification, and seasonal time. The developed approach for the algorithm’s verification is presented as well, together with some preliminary results obtained from TanDEM-X data. The generation of up to-date backscatter models for X-Band will provide a useful data base for the development of a large number of scientific applications and for the optimization of future radar systems.

Carolina Tienda Herrero "Reflectarray Antennas in Dual Reflector Configuration"

Dienstag, 07. Mai 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Recent work on dual-reflector antennas involving reflectarrays is reviewed. Both dual-reflector antenna with a reflectarray subreflector and dual-reflectarrays antennas with flat or parabolic main reflectarray are considered. First, a general analysis technique for these two configurations is described. Second, results for beam scanning and contoured-beam applications in different frequency bands are shown and discussed. The performance and capabilities of these antennas are shown by describing some practical design cases for radar, satellite communications and direct broadcast satellite (DBS) applications.

Ulrich Steinbrecher "WideScanSAR - ein neuer Aufnahmemode für TerraSAR-X"

Dienstag, 30. April 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Bald soll es für die TerraSAR-X Mission zwei neue Aufnahmemoden geben, Staring-Spotlight und Wide-ScanSAR. Hier werden das Design des Wide-ScanSAR Modes und erste Testaufnahmen präsentiert. Zu optimieren galt es die Steifenbreite in Abhängigkeit der klassischen SAR Parameter, Range Ambiguity Ratio, Azimuth Ambiguty Ratio und des Noise Equivalent Sigma Zero unter Berücksichtigung der Einschränkungen, die durch die TSX-1 und TDX-1 Satelliten gegeben sind. Durch Wechseln von festen zu variablen Beambreiten und der Minimierung von Reserven konnte ein Mode designed werden, der eine variable Streifenbreite von 200-250 km hat, ohne die Robustheit bzgl. Topografievariation zu verschlechtern.

Martina Gabele "Synthetic Aperture Radar / Ground Moving Target Indication for Spacebased Radar with Two-Dimensional Antenna Arrays"

Freitag, 26. April 2013
15.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Synthetic Aperture Radar / Ground Moving Target Indication (SAR / GMTI) is an active radar remote sensing technique, based on the coherent combination of SAR imaging and antenna array processing. The SAR / GMTI technique provided a step forward in quantitative ground motion parameter estimation. In the last two decades, airborne SAR / GMTI experiments, and in the last years also spaceborne SAR / GMTI experiments evaluated the potential of the SAR / GMTI techniques to estimate ground motion parameters (i.e. target position, velocity, and motion direction). This dissertation addresses the actual status, the potentials and limitations of spaceborne SAR / GMTI with single / monostatic platforms carrying two-dimensional antenna arrays. The SAR processing is applied in order to generate high resolution images of the target signals, antenna array processing in along-track direction is applied for GMTI and antenna array processing in across-track direction in order to cover large swathes. This trade-off between SAR imaging capability, GMTI capability and swath coverage requires a careful design of radar systems and operation modes. Therefore, one main goal of this dissertation is to provide new spaceborne radar system designs and operation modes which provide a good trade-off between GMTI capability and swath coverage, and furthermore a high flexibility in adjusting between SAR capability and GMTI capability. One considered future SAR system is Astrium’s High Resolution Wide Swath Reference System. Another system is a radar design which is characterized mainly by a largely increased beamsteering capability. Besides, one secondary objective of this dissertation were to extend the signal modeling for combining SAR imaging and antenna array processing in spaceborne geometries. Another secondary objective was to calibrate the first available spaceborne SAR / along-track array experimental data, namely the data from the TerraSAR-X dual receive antenna mode. Lastbut not least, another secondary objective of this dissertation was to demonstrate the validity of the signal and performance modeling by processing the data from airborne and spaceborne experimental campaigns.

Rolf Scheiber "Multi Phase Center Antenna Processing of Ice Sounding Radar Signals for Across Track Surface Clutter Cancellation"

Dienstag, 23. April 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
ESA’s POLarimetric Airborne Radar Ice Sounder demonstrator (POLARIS) – built, maintained and deployed by the Technical University of Denmark (DTU) - operates at P-band and features a multi-phase-center antenna for the purpose of surface clutter suppression. The first data suitable for the development and demonstration of surface clutter cancellation methods were acquired in February 2011 during the IceGrav campaign in Antarctica. The purpose of the present study was to investigate and compare different methods for surface clutter cancellation and to implement a Processing Tool to augment the along-track POLARIS processor developed by ESA, thus improving bedrock detectability. Four algorithms have been selected for implementation and analysis: the standard beamformer, two different clutter nulling algorithms and the optimum beamformer. Prior to the analysis with real POLARIS data the algorithms have been implemented in a simulation environment, allowing for a performance analysis concerning the different input parameters. These included pulse bandwidth, aircraft roll, cross-track terrain slopes, as well as POLARIS antenna patterns. The improved performance of the nulling and optimum beamformer techniques for surface clutter suppression compared to standard beamformer has been demonstrated and requirements on the knowledge of slope and roll parameters have been quantified. By means of simulation it was shown that the relatively large separation of the POLARIS phase centers (~lambda) is responsible for regions of high noise scaling around +/- 45deg off-nadir angle, which turned out to be annoying in particular for the application of the nulling techniques. The optimum beamformer instead is able to better handle these angular regions. The clutter suppression performance has also been demonstrated with the available POLARIS data from the IceGrav 2011 campaign. For all 4 available data takes a clear improvement in clutter suppression performance could be achieved, independent of the signal bandwidth. It was shown that, in terms of clutter suppression, the advanced methods (nulling and optimum beamformer) outperform the standard beamformer by up to 15 dB. However, it was also shown that a major limitation for the performance is the lack of a highly accurate ice surface model. For the purpose of this study it was necessary to rely on ASTER2 GDEM, as no Laser altimetry data from IceGrav were available in time.

Michelangelo Villano "Staggered-SAR: High-Resolution Wide-Swath Imaging by Continuous PRI Variation"

Tuesday, 05 March 2013
2 p.m. Large seminar room at HR Institute, Building 102

Abstract:
Synthetic aperture radar (SAR) is a remote sensing technique, capable of providing high resolution images independent of weather conditions and sunlight illumination. This makes SAR very attractive for the systematic observation of dynamic processes on the Earth’s surface. However, conventional SAR systems are limited, in that a wide swath can only be achieved at the expense of a degraded azimuth resolution. This limitation can be overcome by using systems with multiple receive apertures, displaced in along-track, but a very long antenna is required to map a wide swath. If a relatively short antenna with a single aperture in along-track is available, it is still possible to map a wide area using multiple elevation beams, but “blind ranges” are present across the swaths. Staggered-SAR is an innovative concept, based on the continuous variation of the pulse repetition interval (PRI), which allows high-resolution imaging of a wide continuous swath without the need for a long antenna with multiple apertures.
The presentation will introduce the Staggered-SAR concept and then focus on the design of PRI sequences, the pre-processing of the raw data and the resulting system performance.

Christopher Wecklich "DEM_Library: Generic DEM Access Library for IDL"

Dienstag, 09. April 2013
14.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
Correctly accessing Digital Elevation Models (DEM) can be a difficult challenge. Various DEMs exist, most of them with the corresponding Height Error Model (HEM) files, but some not. These DEM/HEM pairs contain various pixel sizes (in arcseconds), various height systems (Ellipsoid/Geoid), and various file sizes. To support the correct accessing of DEMs, the DEM Library IDL Object is a handy tool to access common DEMs and HEMs, for example, the SRTM. In addition to easy DEM data retrieval, this tool provides more sophisticated functions for SAR analysis, for example, a ray-intersection calculation function with the DEM surface. In this seminar, a general introduction to the DEM Library will be presented along with several examples demonstrating how the functions could be utilized. This will be followed with an introduction to the updates and new features in the last revision of the DEM Library. In order to better understand the overall DEM-Database, we will finish off with a review the various available DEMs therein, and finally review the two different height systems used in the DEM database.

Tilo Wiese "Potentielle Anwendungen moderner Inpainting-Algorithmen für die Verarbeitung von Höhenmodellen in der Fernerkundung"

Dienstag, 19. März 2013
10.00 h Großer Besprechungsraum HR, Gebäude 102

Abstract:
In der Fernerkundung spielen digitale Höhenmodelle eine wichtige Rolle. Sie werden auch in vielen weiteren Bereichen der Forschung und der Industrie für die Weiterverarbeitung und Herstellung von hoch genauen Produkten verwendet. Besonders in der Forschung ist man aber darauf bedacht, stets die höchstmögliche Qualität zur Verfügung zu haben, um weiterführende Ergebnisse bestmöglich umsetzen zu können. Was soll man aber machen, wenn das Testgebiet größere Ausmaße hat, als das zur Verfügung stehende hoch genaue Höhenmodell? Soll auf das niedriger aufgelöste Modell zurückgegriffen werden? Man kann Höhenmodelle unterschiedlicher Genauigkeit zusammenrechnen. Ein Problem stellt hierbei nur die Kante der unterschiedlichen Höhenmodelle dar, da dort ein Höhenversatz auftritt. Hier kann man mit klassischen Interpolations-Algorithmen Abhilfe schaffen und diese Bereiche miteinander verrechnen. Oder was soll man machen, wenn in der SAR-Interferometrie schlechte Kohärenz auftritt, man aber trotzdem ein bestmögliches Höhenmodell benötigt? Auch hier helfen Interpolationsalgorithmen. Ein moderner Ansatz kommt aus der digitalen Bildverarbeitung. Die sogenannten Inpainting-Verfahren benutzen umfassende Kanteninformationen, um den fehlerhaften Bereich im Bild zu rekonstruieren. Sie rekonstruieren Texturen, oder versuchen Linien gleicher Helligkeit zu vervollständigen. Im Laufe dieser Arbeit wird einer dieser Inpainting-Algorithmen näher vorgestellt und für die Verwendbarkeit in der Fernerkundung überprüft. Für eine generelle Verwendbarkeit werden Anpassungen an verschiedenen Parametern des Algorithmus vorgenommen, und es wird die Verwendung einer Bildpyramide umgesetzt. Um die Rekonstruktionseigenschaften zu überprüfen, werden direkte Vergleiche zwischen klassischen Interpolations-Algorithmen und dem gewählten Inpainting-Algorithmus basierend auf den unterschiedlichsten Datensätzen durchgeführt, um die Genauigkeit bei wechselnder Topographie zu untersuchen. Es werden weiterhin reale Beispiele durchgerechnet, um Qualitätsunterschiede zwischen den synthetischen Beispielen und der Realität auszuschließen, oder sichtbar zu machen. Zuletzt soll die Eignung auf zuvor erwähnte Fusion digitaler Höhenmodelle untersucht werden und in einem qualitativen Vergleich validiert werden.

Ali Eren Culhaoglu "Microwave Metamaterials: Superlensing and Design of Low Reflection Coatings"

Tuesday, 12 March 2013
2 p.m. Large seminar room at HR Institute, Building 102

Abstract:
Metamaterials are artificially engineered materials that have properties not attainable with naturally occurring materials, such as a negative refractive index. They enable the design of novel microwave devices, which cannot be realized on the basis of naturally occurring materials. The imaging properties of a metamaterial superlens and the design of metamaterial low reflection coatings are investigated in this work. A planar negative refractive index metamaterial slab focuses waves emitted from a Hertzian dipole to an image plane behind the slab. A resolution beyond that of conventional imaging systems is thereby achieved. The imaging characteristics of the superlens are investigated analytically in the spectral domain by expressing the fields as a Fourier integral. A novel approach for the realization of Drude and Lorentz dispersive metamaterial radar absorbers is presented. A metamaterial based anti-reflection coating is realized and studied experimentally.

Julia Stockamp "Multi-Frequency Analysis of Snow covered Areas using SAR Polarimetry"

Tuesday, 26 February 2013
2 p.m. Large seminar room at HR Institute, Building 102

Abstract:
Monitoring of Earth‘s snow reservoirs and their dynamic over time is increasingly important in the context of climate change. The large scale retrieval of snow parameters, such as snow water equivalent (SWE), can provide essential information about fresh water resources. In this multi-frequency analysis of C-band (quad-pol), X-band (dual-pol) and Ku-band (dual-pol) data of snow cover in Sodankylä, Finland, SWE is retrieved for a time series within the winter season 2011/2012. For that purpose, the CoReH2O forward model and inversion techniques are used. It is analyzed, how the different frequencies perform in a single frequency approach, and in particular, what C-band can contribute to a SWE inversion. By comparing dual-pol with quad-pol data, it is examined, whether there is an advantage of decomposing the total backscatter into volume and ground surface components and, subsequently, of using only the volume backscattering in the inversion process for SWE. The multi-frequency SAR data are complemented by ground measurements of SWE, snow depth and various meteorological and hydrological parameters for analysis and validation. Results show that in X-band the measured upward trend of SWE is partly reproduced in the dual-pol approach. It was found that C-band in dual-pol as well as quad-pol configuration performs unsatisfactorily in comparison to X-band for SWE retrieval. A polarimetric eigen-analysis of the quad-pol C-band data, however, reveals a significant correlation to the underlying soil and its freezing and thawing processes and not to snow cover. Hence, it is easily possible to establish a robust correlation between the polarimetric entropy/alpha values and the dielectric constant of the (snow covered) soil including the entire winter period.

Anita Pollner "DEM based shadow & layover detection using Python"

Tuesday, 29 January 2013
2 p.m. Large seminar room at HR Institute, Building 102

Abstract:
The generation of Digital Elevation Models (DEMs) is one of the biggest applications for SAR interferometry. While SAR DEMs generally have highly accurate landscapes with high relief energy, they are subject to shadow/layover effects originating from the acquisition geometry. In the course of a 3-month internship, a software for the identification of shadow/layover areas based on reference DEMs was implemented. Python was chosen as the programming language for this software in order to gather first-hand experience.