Helmut Süß

Efficient and precise processing for squinted spotlight SAR through a modified stolt mapping

Processing of squinted SAR spotlight data is a challenge because of the significant range migration effects of the raw data over the coherent aperture time. Although in theory the ()-algorithm takes care of these aspects, its digital implementation requires a time-consuming interpolation step. Moreover, the limited precision of this interpolation can introduce distortions at the edges of the final image especially for squinted geometries. A wave number domain processing using a modified Stolt mapping will be developed and analyzed to enhance the quality of the final SAR image. Additionally, the proposed algorithm has a decreased computational load compared to the original ()-algorithm. Simulation results will validate the focusing and efficiency performances of the modified wave number domain algorithm.

Study of passive MMW personnel imaging with respect to suspicious and common concealed objects for security applications

Microwaves in the range of 1-300 GHz are used in many respects for remote sensing applications. Besides radar sensors particularly passive measurement methods are used for two-dimensional imaging. The imaging of persons and critical infrastructures for security purposes is of increasing interest particularly for transportation services or public events. Personnel inspection with respect to weapons and explosives becomes an important mean concerning terrorist attacks. Microwaves can penetrate clothing and a multitude of other materials and allow the detection of hidden objects by monitoring dielectric anomalies. Passive microwave remote sensing allows a daytime independent non-destructive observation and examination of the objects of interest under nearly all weather conditions without artificial exposure of persons or areas. Some millimeter-wave radiometric imaging devices with respect to low cost are investigated. Measurement results of some typical personnel screening scenarios are discussed. Requirements for future operational systems are outlined.

An end-to-end simulator for high-resolution spaceborne SAR systems

The purpose of this paper is to present an end-to-end simulator for spaceborne high-resolution SAR systems that is capable of simulating realistic raw data and focused images of extended three-dimensional scenes. The simulator is based on precise mathematical modeling of an overall SAR system chain and generates information on the quality of the image data and its suitability to interpret target and background signatures. The principal components of the simulator are: - the generation of an extended scene, including the fully polarimetric scattering behavior of the three-dimensional surfaces, man made objects, and the typical SAR effects like overlay, speckle noise, shadowing;-an accurate SAR sensor simulation (antenna, transmit and receive path);-the generation of the raw data depending on the desired SAR mode (stripmap, spotlight mode);-the image processing and evaluation. The flexible and modular structure allows for adjustment and extension to fulfill different tasks. The most important modules reflecting the basic physical models will be described and simulation results will be demonstrated.

The monitoring of critical infrastructures using microwave radiometers

Microwaves in the range of 1-300 GHz are used in many respects for remote sensing applications. Besides radar sensors particularly passive measurement methods are used for two-dimensional imaging. The imaging of persons and critical infrastructures for security purposes is of increasing interest particularly for transportation services or public events. Personnel inspection with respect to weapons and explosives becomes an important mean concerning terrorist attacks. Microwaves can penetrate clothing and a multitude of other materials and allow the detection of hidden objects by monitoring dielectric anomalies. Passive microwave remote sensing allows a daytime independent non-destructive observation and examination of the objects of interest under nearly all weather conditions without artificial exposure of persons or areas. The performance of millimeter-wave radiometric imaging with respect to wide-area surveillance is investigated. Measurement results of some typical critical infrastructure scenarios are discussed. Requirements for future operational systems are outlined exploring a radiometric range equation.

Fully-polarimetric passive MMW imaging systems for security applications

Increasing terroristic attacks raise the danger to the public and create a new and more complex dimension of threat. This evolution must and can only be combat by the application of new counter-measures like advanced imaging technologies for wide-area surveillance and the detection of concealed dangerous objects. Passive microwave remote sensing allows a daytime independent non-destructive observation and examination of the objects of interest under nearly all weather conditions. The acquisition of polarimetric object characteristics can increase the detection capability by gathering complementary object information. Over years the DLR Microwaves and Radar Institute developed several problem-orientated radiometer imaging systems covering nearly the whole frequency spectrum between 1 GHz and 100 GHz for a multitude of applications. Actually a fully-polarimetric radiometer receiver at W band is developed in order to explore the polarimetric information content of interesting objects simultaneously. Some important theoretical characteristics of polarimetric radiometry at millimeterwaves are introduced and discussed. The actual design and construction of the receiver system is outlined and first experimental imaging results are presented.

Analysis of SAR images by simulation

Accurate simulation tools for the design of space borne synthetic aperture radar systems (SAR) are compulsory for the analysis of the systems capabilities, because ground based experimental tests are in most cases impossible and very costly. Through a simulation process it is possible to analyze the image quality parameters for a given system configuration or evaluating the effects in SAR images when this configuration is changed. A new fast SAR image simulator (SARIS) is currently under development on the basis of an existing toolset called SAR end-to-end simulator (SETES). This image simulator produces SAR images by using the point spread function (PSF) of a focused point target response in contrast to SETESs very expensive raw data generation module. In SARIS the SAR image is produced through a convolution of the PSF with the so-called reflectivity map of the scene. In this paper first simulation results with a prototype of SARIS are given to show effects like motion errors and low peak-to-side-lobe ratios.

Detection of anti-personnel landmines using microwave radiometry techniques

At present many million anti-personnel (AP) mines are polluting our environment in many countries. They cause a considerable limitation of the living space and make the land unuseable for agricultural purposes. Because the mine clearance procedures are much slower than the mine laying operations the number of polluting mines and the related contanimated areas are nowadays still increasing. Many mine polluted regions are former combat areas or belong to formerly highly frequented places. Thus the ground is contaminated additionally by many artificial impurities. For the current mine detection technologies and for the most modern mines, which become continuously smaller and have less metal content, a high false alarm rate of up to 1000 to 1 is therefore very likely.

Results and experiences from the NATO Common Shield DAT#7 experiment for the Defence Against Terrorism program

Passive microwave imaging allows a daytime independent observation and examination of objects and persons without artificial exposure under nearly all weather conditions. The penetration capability of microwaves allows the detection of hidden objects like weapons and explosive devices under the clothing. In August/September 2008 a comprehensive military experiment was conducted by the German armed forces at the naval base Eckernfoerde, Germany. One activity in the Eckernfoerde trial was the simulation of a military entrance portal by a tent including various imaging and a chemical sensor suite. Besides commercial optical and infrared cameras various passive millimeter-wave imagers have been used from different German research institutions. The DLR Microwaves and Radar Institute, Department for Reconnaissance and Security (HR-AS), provided an imaging radiometer scanner operating at W band. A multitude of situations have been simulated and many persons carrying hidden objects under their clothing have been scanned. Some exemplary results from the trial are shown and discussed in the paper.