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Vorträge im Institutsseminar 2012
Marc Rodriguez Cassola "Bistatic Synthetic Aperture Radar Data Processing"
Dienstag, 11. Dezember 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Bistatic SAR systems offer a number of operational advantages when compared to their monostatic counterparts, e.g., flexible imaging geometries, possibility of sharing a common transmitter, better cost efficiency, increased performance, simplicity of hardware, or silent operation. The previous benefits are very interesting for both military and civilian systems, including among others, improved target detection and classification systems, forward-looking or stationary imaging, single-pass SAR interferometric or tomographic systems, as well as super-resolution or wide-swath systems. Due to these reasons, bistatic SAR systems will play a major role in the next generation of spaceborne SAR systems.
The primary purpose of the thesis has been to develop algorithms for the precise and efficient processing of bistatic SAR data, understood as the ensemble of mathematical operations necessary to reconstruct an accurate bistatic complex reflectivity image. Similarly, the previous formulation can be separated in four different tasks:
• Identification of the essential aspects of bistatic SAR having an impact on the final quality of the reconstructed images.
• Development of precise and efficient algorithms accurately coping with the particularities of the bistatic acquisitions.
• Analysis of the performance of the developed algorithms..
• Validation of the algorithms with actual bistatic data..
The thesis addresses the essential aspects of bistatic SAR processing for both airborne and spaceborne systems. Although the core of the research is the development of processing algorithms, the thesis also concentrates on other interesting aspects of bistatic SAR like performance analysis tools or the presentation of innovative bistatic SAR experiments. Last but not least, the proposed algorithms are tested with real bistatic data, which illustrates and demonstrates the appropriateness of the approaches for actual bistatic SAR missions. As I see it, the main original contributions of this work to the existing literature on bistatic SAR are the following:.
• The presentation of innovative airborne and spaceborne bistatic SAR experiments, including the evaluation of the acquired data. These experiments encompass the first cross-platform bistatic airborne SAR interferometric acquisition with RAMSES and E-SAR, the first high-resolution bistatic spaceborne-airborne SAR acquisition between TerraSAR-X and F-SAR, and the first bistatic SAR interferometric experiments in space with TanDEM-X..
• The development of algorithms for the automatic synchronisation of bistatic SAR data. The synchronisation of bistatic SAR data with the only help of the analysis of the received data is addressed in this work for the first time. Analytical expressions of the performance of the proposed algorithms are also included..
• The development of a precise and efficient image formation algorithm for general bistatic SAR configurations with exact accommodation of azimuth-variance and terrain topography. The presented algorithm is the first in the literature capable of focussing general bistatic SAR data in a precise manner..
All the individual contributions considered, the present work puts forward a sound formulation for the data processing of existing and future bistatic SAR systems in general configurations.
Daniel Rudolf, Stephan Dill "SUMIRAD – A fast imaging MMW radiometer system"
Dienstag, 04. Dezember 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
In the frame of the SUM project (Surveillance in an urban environment using mobile sensors) a cost-effective multi-sensor vehicle based surveillance system was developed in order to enhance situational awareness of patrol vehicles. For reliable system operation under various sight conditions (dust, fog, smoke, rain) and enhanced information gathering, different types of sensors are applied, the complementarities of which are exploited through an advanced data fusion engine. The sensor suite includes an optical and an infrared camera, millimeter-wave radar and a millimeter-wave imaging radiometer. The latter SUM Imaging Radiometer (SUMIRAD) has been developed by DLR Microwaves and Radar Institute and is able to provide quasi-optical two-dimensional microwave images in almost real-time.
The SUMIRAD system offers the advantage to detect and localize objects and persons under atmospheric obstacles and also extents the surveillance capabilities behind non-metallic materials like clothing or thin walls and thin vegetation. SUMIRAD is an innovative and light-weight fully mechanical scanner using two W-band radiometer receivers. It accomplishes the demand to cover a large field of view at high performance for reasonable cost.
The presentation will give an overview on the development of the SUM imaging radiometer system and its key components. Furthermore the image processing of the final image product and the fast automatic object detection algorithm will be described. Imaging results from several measurement campaigns (e.g. threat detection, weather observation, through wall imaging) will be presented.
Jovana Balkoski "Nadir Echo Properties and Suppression in Spaceborne Synthetic Aperture Radar Systems - a Study Based on TerraSAR-X Data"
Dienstag, 30. Oktober 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
In images obtained by spaceborne Synthetic Aperture Radar (SAR) systems the Nadir echo, i.e. the signal received from the area surrounding the point with the closest distance to the satellite, is an unwanted effect. For a known altitude and ground geometry, it is possible to avoid Nadir echo by carefully choosing the pulse repetition frequency (PRF). This constraint reduces the degrees of freedom and represents a significant drawback especially for the forthcoming generation SAR systems, conceived for high resolution and wide swath imaging. This has recently motivated on one side the development of digital filter techniques for Nadir echo suppression and on the other side the studies on Nadir echo physical features.
This work investigates the properties of the Nadir echo. The analysis is based on a selected spaceborne SAR data set, obtained with the TerraSAR-X system. The Nadir features in terms of duration, amplitude, phase, frequency and its behaviors, as point or distributed target, are studied and examined based on raw, range compressed and image data analysis.
SeungKuk Lee "Forest Parameter Estimation Using Polarimetric SAR Interferometry Techniques at Low Frequencies"
Freitag, 19. Oktober 2012
10.30 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Polarimetric Synthetic Aperture Radar Interferometry (Pol-InSAR) is an active radar remote sensing technique, based on the coherent combination of both polarimetric and interferometric observables. The Pol-InSAR technique provided a step forward in quantitative forest parameter estimation. In the last decade, airborne SAR experiments evaluated the potential of Pol-InSAR techniques to estimate forest parameters (e.g. forest height and biomass) with high accuracy over various local forest test sites.
This dissertation addresses the actual status, the potentials and limitations of Pol-InSAR inversion techniques for 3-D forest parameter estimations on a global scale using lower frequencies, like L- and P-band.
The multi-baseline Pol-InSAR inversion technique is applied to optimize the performance with respect to the actual level of the vertical wave number and to mitigate the impact of temporal decorrelation on the Pol-InSAR forest parameter inversion.
Temporal decorrelation is a critical issue for the successful Pol-InSAR inversion in the case of repeat-pass Pol-InSAR data, as provided by conventional satellites or airborne SAR systems. Despite the limiting impact of temporal decorrelation in the Pol-InSAR inversion, it remains a poorly understood factor in the forest height inversion. Therefore, one main goal of this dissertation is to provide a quantitative estimation of temporal decorrelation effects by using multi-baseline Pol-InSAR data. A new approach to quantify different temporal decorrelation components is proposed and discussed. Temporal decorrelation coefficients are estimated for temporal baselines ranging from 10 minutes to 54 days and are converted to height inversion errors.
Besides, the potential of Pol-InSAR forest parameter estimation techniques are addressed and projected onto future spaceborne system configurations and mission scenarios (Tandem-L and BIOMASS satellite missions at L- and P-band). The impact of system parameters (e.g. bandwidth, NESZ, ambiguities) and operation scenario (e.g. temporal decorrelation due to repeat-pass orbit) is evaluated and discussed with respect to the retrieval of forest parameters.
The study is supported and validated by using repeat-pass Pol-InSAR data at L- and P-band acquired by DLR’s E-SAR system over Remningstorp (BioSAR 2007, hemi-boreal forest) and Krycklan (BioSAR 2008, boreal forest) as well as over Traunstein (TempoSAR 2008 and 2009, temperate forest) test sites. The simulated spaceborne data sets generated during the BioSAR 2007 campaign are used to carry out the performance analysis.
Gordon Farquharson of Applied Physics Laboratory - University of Washington "Microwave remote sensing at APL-UW"
Montag, 30. Juli 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Microwave remote sensing in the Air-sea Interaction Remote Sensing Department (AIRS) at APL-UW focuses mainly on ocean physics. This talk will focus on two projects currently in progress. First, results from a newly developed C-band dual-beam along-track synthetic aperture radar for nearshore ocean and riverine measurements will be presented. The results will focus on the data we collected data over the New River Inlet in North Carolina in May earlier this year. Then, a new shipborne radar designed for wave retrieval will be discussed. This instrument will be the primary sensor in a ship motion prediction system being prototyped for the Office of Naval Research. The presentation will focus on the sensor, and the wave field retrieval algorithm, and present results from simulated and field data.
Vinicius Queiroz de Almeida "Study of Medium Earth Orbit and Geostationary Synthetic Aperture Radar"
Mittwoch, 18. Juli 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
In the latest few decades, satellite based Earth observation has established itself as an irreplaceable tool to monitor a wide range of geophysical phenomena. The steadily growing use and interest in these space-borne measurements naturally leads to increasingly demanding observational requirements, converging towards a demand for global coverage with high spatial resolution and fine temporal sampling.
Most Earth observation satellites operate in Low Earth Orbits (LEO), typically with orbit heights between 500 km and 800 km. For optical and hyperspectral systems or microwave radiometers, low orbit heights are favorable in terms of spatial resolution, which is given by the aperture-driven angular resolution multiplied by the distance to the observed area. In the case of Synthetic Aperture Radar (SAR), low orbit heights are favorable in terms of system sensitivity (or power budget), since the free space propagation loss term in then minimized.
A clear drawback of LEO is that the field of view for a given spacecraft is small. As a result, global coverage can only be obtained after a relatively long orbit repeat cycle. This limits the capability of LEO SAR systems to provide observations over large areas with a high temporal sampling.
Several works have studied the possibility of overcoming this shortcomings, thus obtaining wide area coverage and fine temporal sampling, using a SAR system in a Medium Earth Orbit (MEO) or even in geosynchronous orbits. The main enabling concept is that as the orbit height increases, the angular velocity of the spacecraft with respect to a target on the Earth surface decreases, which leads to a longer integration time. In the extreme case of geostationary orbits, where the spacecraft drifts around a nominal fixed position with 24 hours periodicity, this integration can be of hours (in comparison, the integration time for a typical LEO SAR system in in the order of 1 second). These long integration times compensate, to a large extent, large propagation losses, leading to feasible system requirements.
The objective of this work was to study in detail the system performance trade-offs for MEO and GEO SAR-systems. Besides this general study, and output of this project was some mission concepts, which will be shown in the presentation.
Thomas Jagdhuber "Soil parameter retrieval under vegetation cover using SAR polarimetry"
Dienstag, 03. Juli 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Soil conditions under vegetation cover and their spatial and temporal variations from point to catchment scale are crucial for understanding hydrological processes within the vadose zone, for managing irrigation and consequently maximizing yield by precision farming. Soil moisture and soil roughness are the key parameters that characterize the soil status. In order to monitor their spatial and temporal variability on large scales, remote sensing techniques are required. Therefore the determination of soil parameters under vegetation cover was approached by means of (multi-angular) polarimetric SAR acquisitions at a longer wavelength (L-band). The penetration capabilities of L-band are combined with newly developed (multi-angular) polarimetric decomposition techniques to separate the different scattering contributions, which are occurring in vegetation and on ground. Subsequently, the ground components are inverted to estimate the soil characteristics.
The developed algorithms are validated with fully polarimetric SAR data acquired by the airborne E-SAR sensor for three different study areas in Germany. The achieved results reveal inversion rates up to 99% for the soil moisture and soil roughness retrieval in agricultural areas. The validation against simultaneously acquired field measurements indicates an estimation accuracy (root mean square error) of 5-10vol.% for the soil moisture (range of in situ values: 1-46vol.%) and of 0.37-0.45cm for the soil roughness (range of in situ values: 0.5-4.0cm) within the catchment. Hence, a continuous monitoring of soil parameters along the growing season is possible within the obtained precision.
Carolina Tienda Herrero "Analysis and design of antennas in dual-reflectarrray configuration"
Donnerstag, 21. Juni 2012
11.30 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Reflectarrays antennas have demonstrated their benefits with respect to classic reflector antennas for certain applications. Reflectarrays exhibit capabilities to provide high-gain focused beams in large apertures, contoured beams for DBS applications or beam scanning. They provide a low profile solution for all these applications since they use printed-circuit technology which reduce the manufacturing cost in particular for shaped-beam space antennas.
Dual-reflectarray antennas comprising a main reflectarray and an offset-placed sub-reflectarray present some other additional advantages, since the additional degrees of freedom of adjusting the phase on both surfaces can be used to improve the antenna performance. This seminar will show a dual-reflectarray antenna demonstrator designed to provide broad-band operation and very low levels of cross-polarization by exploiting the degrees of freedom of adjusting the patch dimensions on both reflectarray surfaces.
Dr. Keith Morrison "Distinguishing Between Surface and Sub-Surface Features in SAR Imagery"
Dienstag, 19. Juni 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
We report on SubSAR, a new application of DInSAR for the discrimination between surface and sub-surface features, at large stand-off distances applicable to airborne and satellite measurements. This is in sharp contrast to current techniques, where discrimination relies on close-in measurement of the scene, usually by scanning across the surface with a ground-penetrating radar to spatially isolate, vertically, the surface and sub-surface backscatter returns. As such, range-layover severely limits practical stand-off distances. The new scheme utilises the natural variation in soil moisture above a buried feature, and the concomitant changes in signal retardation measured through phase, to discriminate between surface and sub-surface returns.
Verena Huber Garcia "Physical Reasons for Outliers in TanDEM-X DEMs"
Mittwoch, 2. Mai 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The TanDEM-X mission, now in its second year, is designed to generate a high resolution Digital Elevation Model of the Earth with unprecedented accuracy. Even if statistical analyses are routinely conducted to assess the quality of the products, we still lack a detailed understanding of DEM errors on a local scale.
In this work some raw DEM products were analyzed in detail in order to identify possible errors. The analyses were conducted by inspecting single DEMs, or by comparing them with optical imagery or with other DEMs of the same area (either with a second TanDEM-X DEM or with SRTM).
In a second step, the physical reasons for these differences and outliers were investigated in a field work in order to improve the understanding of errors that can occur in TanDEM-X data. Several examples of outliers in TanDEM-X DEMs and their probable causes will be shown in the presentation.
Andreas Hölderlin "Road to Market – ein Werkzeug zur Steigerung der Innovationsfähigkeit"
Dienstag, 17. April 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
In dem Innovations-System des DLR sind unsere Innovationsziele und Innovationsprozesse verankert. Ein Innovationsziel ist es, möglichst viele DLR- Kompetenzen und –Technologien in den Markt zu bringen. Um die Organisationseinheiten des DLR bei ihrer Innovationstätigkeit und bei dem Erreichen der Innovationsziele zu unterstützen, sind in der Abteilung Technologiemarketing (TM) Werkzeuge entwickelt worden und auch bereits in der erfolgreiche Anwendung.
Heute möchten wir Ihnen das Werkzeug Road to Market (R2M) vorstellen. R2M ist ein Werkzeug, welches das Innovations- bzw. das Marktpotential von (Forschungs-)Themen systematisch und transparent analysiert und quantifiziert und damit eine diesbezügliche Wertung und Rangfolge von Themen ermöglicht. Weiterhin unterstützt R2M dabei, Kompetenzen oder Technologien effektiv und effizient in den Markt zu bringen.
R2M wird im Allgemeinen operativ durch TM für Sie als Dienstleistung erbracht, wobei natürlich Ihre Beiträge bei der Aufnahme und Bewertung Ihrer fallspezifischen Daten erforderlich sind.
Miguel Kohling "Validation of Soil Moisture Retrieval from Fully Polarimetric F-SAR L-Band Data"
Dienstag, 03. April 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Soil moisture is of great importance for land-atmosphere feedbacks, affecting evaporation rates as well as the conversion of incoming radiation into heat, and for allocation of precipitation into surface runoff, infiltration and percolation within the pedosphere. The knowledge of its spatial distribution and temporal variability enhances drought prediction in agriculture and forestry, optimizes agricultural irrigation, supports flooding hazard control and can be used as input in hydrological and climate models. Therefore soil moisture is considered as an essential climate variable by the Global Climate Observing System (GCOS).
In this master thesis soil moisture retrieval under vegetation cover is studied and validated using fully polarimetric SAR data. The data were acquired at L-band over three different TERENO (Terrestrial Environmental Observatories) test sites by DLR’s novel airborne F-SAR sensor within the TERENO measurement campaign in May and June 2011. Simultaneously to the aerial survey, in-situ data were collected by mobile soil moisture probes and by SoilNet clusters within the three observatories (Ammer, Bode and Rur catchment). Due to the different catchment conditions several hydrological situations could be captured and analysed.
For the soil moisture retrieval newly developed, polarimetric decomposition and inversion algorithms are applied. A model-based and a hybrid decomposition algorithm were compared and validated for their potentials and limitations to invert soil moisture under vegetation cover.
Dr. Junghyo Kim "An Overview of Multi-Channel Airborne SAR Systems"
Dienstag, 13. März 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Airborne Synthetic Aperture Radar (SAR) has been contributing to measuring physical parameters of targets and supporting spaceborne SAR missions in preliminary system design, signal processing and technology development. Furthermore, recent airborne SAR systems play an important role in the development and demonstration of novel SAR techniques, such as digital beamforming (DBF). For this purpose, several institutions and industries in Europe, America and Asia are accelerating new airborne system development, which employ multiple antennas combined with DBF capability.
In this presentation, we make a review of these existing and developing airborne DBF SAR systems in terms of design goal, system architectures and operation modes. The review is going to tell us that the DBF enables to the implementation of multimodal operation in airborne SAR systems as well as new radar imaging modes. Based on the review, we also discuss a potential airborne DBF SAR system concept and operation modes in order to support the F-SAR DBF system design.
Prof. Ingmar Kallfass (KIT) "Advanced MMIC-Based Frontends for Millimeter-Wave Sensing and Communication"
Dienstag, 7. Februar 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Active monolithic integrated circuits today cover the entire millimeter-wave frequency range, bringing important advantages such as compactness and cost effectiveness to the implementation of analog frontends for high resolution sensing and high data rate communication applications. This presentation covers the design and performance of advanced MMIC-based analog frontends in state-of-the-art GaAs and millimeter-wave GaN HEMT technologies.
The first part describes monolithic integrated active cold and hot loads for the calibration of radiometric sensors in W-band.
In the second part, ongoing work in the frame of the DLR-funded project GISALI will be presented, which investigates the feasibility of future satellite communication links in E-band (71-84 GHz). Link budget calculations and a high performance E-band communication chip-set will be discussed.
Annalisa Della Corte "Snow Properties Retrieval using TerraSAR-X Dual-Polarization Data"
Donnerstag, 19. Januar 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Snow properties and snow cover change monitoring on global scale are needed for a better understanding of the role of the cryosphere in the climate system. Snow plays also an important role in biogeochemical cycles since it is a basic water resource for many densely populated areas of the planet. Snow Water Equivalent (SWE) has been selected as primary parameter to be retrieved in this kind of investigations.
In this work, the capabilities of the SWE (and snowflakes size) retrieval algorithm proposed for the CoReH2O satellite mission are investigated using TerraSAR-X dual-pol data. Experimental airborne SAR data (SnowSAR) are also employed for comparison, while ground measurements from the NoSREx campaign are used for validation.
The considered test site is the Intensive Observation Area (IOA) in the south region of the city of Sodankylae, Lapland, where snowfall can occur between October and May. Our investigation is based on TerraSAR-X acquisitions performed between October 2010 and March 2011. The images were acquired in the strip map mode in the dual-pol (VV - VH) configuration, with an incidence angle of 33°.
A preliminary sensitivity analysis of the CoReH2O radiative transfer model for snowpack characterization has been performed. Then, three dates corresponding to very different values of measured SWE have been chosen to test the CoReH2O algorithms. Both, model and retrieval procedure are adapted for the one frequency (X-band) case.
Results of retrieved SWE and grain size will be shown and discussed in the presentation.
Jens Reimann (Ph.D. TU-Chemnitz) "Calibration and Recent Work on the DLR Weather Radar PolDiRad"
Dienstag, 17. Januar 2012
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The development of the POLDIRAD C-Band weather radar was a joined project between the DLR microwaves and radar institute and the institute for atmospheric physics. It was set up 25 years ago and still has some unique features. Its polarization network enables the radar to transmit any full polarized waves and to switch the polarization basis for each radar pulse independently for receive and transmit. This empowers the radar not only to measure the full scattering matrix of a target, but also to do polarimetric propagation research using a great variety of polarization. The disadvantage of the radar is its complicated design that lacks reciprocity. To overcome this drawback a new polarimetric active radar calibrator (PARC) was developed. Beside this calibration work, other ongoing projects using the POLDIRAD radar will be briefly presented.
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