Maria Greco

Simon Watts

Modeling and Processing of Radar Signals for Earth Observation

Along-track interferometric synthetic aperture radar (AT-InSAR) systems are used to estimate the radial velocity of targets moving on the ground, starting from the interferometric phases, obtained by the combinations of two complex SAR images acquired by two antennas spatially separated along the platform moving direction. Since the radial velocity estimation obtained from a single-phase interferogram (single-channel) suffers from ambiguities, multichannel AT-InSAR systems using more than one interferogram can be used. In this paper, we first analyze the moving target detection problem, evaluating the systems performance in terms of probability of detection and probability of false alarm obtained with different values of target radial velocity, signal-to-clutter ratio, and clutter-to-thermal noise ratio. Then, we analyze the radial velocity estimation accuracy in terms of Cramer-Rao lower bounds and of mean square error values, obtained by using a maximum likelihood estimation technique. We consider the cases of single-baseline and dual-baseline satellite systems, and we evaluate the detection and estimation performance improvement obtained in the dual-baseline case with respect to the single-baseline one. Sensitivity of the presented method with respect to the involved target and system parameters is also discussed.

Alessandra Budillon

Vito Pascazio

Gilda Schirinzi

Multichannel Along-Track Interferometric SAR Systems: Moving Targets Detection and Velocity Estimation

We review experimental evidence for the nonlinearity of sea clutter
and the role of the -parameter or Mann-Whitney rank-sum statistic in
quantifying this nonlinear behavior in the context of a hybrid AM/FM model
for sea clutter, viewed as a cyclostationary process. An independent theoretical
derivation of the stochastic dynamics of radar scattering in a sea clutter
environment, in terms of a pair of coupled stochastic differential equations for
the received envelope and radar cross-section (RCS), enables the identification
of nonlinearity in terms of the shape parameter for the RCS. We are led
to conclude that, from both experimental and theoretical points of view, the
dynamics of sea clutter are nonlinear with a consistent degree of nonlinearity
that is determined by the sea state.

Timothy R. Field

Simon Haykin

Nonlinear Dynamics of Sea Clutter

The coherent temporal characteristics of medium-to-low grazing angle sea clutter and small boat reflectivity are considered for different radar waveforms under a range of environmental conditions and geometrical configurations. Accurate empirical modelling of sea clutter enables the inference of the local sea conditions from radar returns, pertinent for port safety and navigation. Understanding the dynamics and associated reflectivity of small boats, in addition to empirical sea clutter models, allows the development of advanced detection and tracking algorithms, which will improve the performance of surveillance and marine navigation radar against small boats. Work presented is based on the empirical analysis of data recorded with two calibrated, coherent, pulsed radar systems at X-band frequencies. Specifically, target echoes from small boats are included in the datasets and subsequent analysis.

P. L. Herselman

C. J. Baker

H. J. de Wind

An Analysis of X-Band Calibrated Sea Clutter and Small Boat Reflectivity at Medium-to-Low Grazing Angles

This paper is focused on the improvement and further validation of a recently proposed approach for the joint use of radar satellite imagery of an area affected by a major disaster and ancillary data. The study was carried out at different sites on imagery of two different earthquakes occurred one in the Mediterranean coast of Algeria on May 21st, 2003, which severely affected the city of Boumerdes, and one in the Pacific Coast of Peru on August, 15th, 2007. The combination of different radar-extracted features results in very fuzzy classification of the damage patterns, far less detailed than what available using optical imagery. However, focused results using the above-mentioned ancillary data provide enough detail and precision to be comparable with them. In particular, quantized damage level at the block level is achieved at enough detail using ALOS/PALSAR data and thus validates the original idea.

Giovanna Trianni

Paolo Gamba

Damage Detection from SAR Imagery: Application to  the 2003 Algeria and 2007 Peru Earthquakes

A new robust technique for high-resolution reconstructive imaging is developed as required for enhanced remote sensing (RS) with imaging array radar or/and synthetic aperture radar (SAR) operating in an uncertain RS environment. The operational scenario uncertainties are associated with the unknown statistics of perturbations of the signal formation operator (SFO) in turbulent medium, imperfect array calibration, finite dimensionality of measurements, uncontrolled antenna vibrations, and random carrier trajectory deviations in the case of SAR. We propose new descriptive experiment design regularization (DEDR) approach to treat the uncertain radar image enhancement/reconstruction problems. The proposed DEDR incorporates into the minimum risk (MR) nonparametric estimation strategy the experiment design-motivated operational constraints algorithmically coupled with the worst-case statistical performance (WCSP) optimization-based regularization. The MR objective functional is constrained by the WCSP information, and the robust DEDR image reconstruction operator applicable to the scenarios with the low-rank uncertain estimated data correlation matrices is found. We report and discuss some simulation results related to enhancement of the uncertain SAR imagery indicative of the significantly increased performance efficiency gained with the developed approach.

Yuriy Shkvarko

Hector Perez-Meana

Alejandro Castillo-Atoche

Enhanced Radar Imaging in Uncertain Environment: A Descriptive Experiment Design Regularization Approach

Inverse synthetic aperture radar (ISAR) images are often used for classifying and recognising targets. To reduce the amount of data processed by the classifier, scattering centres are extracted from the ISAR image and used for classifying and recognising targets. This paper addresses the problem of estimating the position and the scattering vector of target scattering centres from polarimetric ISAR images. The proposed technique is obtained by extending the CLEAN technique, which was introduced in radar imaging for extracting scattering centres from single-polarisation ISAR images. The effectiveness of the proposed algorithm, namely, the Polarimetric CLEAN (Pol-CLEAN) is tested on simulated and real data.

M. Martorella

A. Cacciamano

E. Giusti

F. Berizzi

B. Haywood

B. Bates

CLEAN Technique for Polarimetric ISAR

The modeling of complex target response in SAR imagery is the main subject of this paper. The analysis of a large database of SAR images with polarimetric and interferometric capabilities is used to accurately establish how the different structural parts of targets interact with the incident signal. This allows to relate the reflectivity information provided by SAR images with specific geometries and to fix variation reflectivity patterns in terms of different imaging parameters such  as image resolution, incidence angle, or operating frequency. Most of the used images have been obtained from the SAR simulator of complex targets developed at UPC, which is able to generate realistic data for a wide range of observation and environmental conditions. The result is a precise scattering-based SAR model that opens the door, among others, to an alternative way for reliable geometry retrieval. Under this approach, a novel SAR classification method for ships has been proposed. The preliminary evaluation in simulated scenarios shows a notable classification capability even under strong clutter and ship motion conditions. Due to these promising results, the same methodology is intended to be applied to urban areas. Concerns about possible model limitations and required improvements are preliminarily treated.

Gerard Margarit

Jordi J. Mallorqui

Scattering-Based Model of the SAR Signatures of Complex Targets for Classification Applications

This paper presents an overview of the research conducted at University of Birmingham. It highlights and briefly discusses various systems parameters (e.g., resolution, power budget), problems (e.g., interference, heterodyne channel Doppler compensation), and signal processing algorithms (imaging, synchronization) required for successfully obtaining an image. The GLONASS satellite is used for experiential confirmation of the main results. All these results are presented and briefly discussed.

M. Cherniakov

Rajesh Saini

Michael Antoniou

Rui Zuo

Eleftherios Plakidis

Experiences Gained during the Development of a Passive BSAR with GNSS Transmitters of Opportunity

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