Alessandro Mori

A time-domain raw signal Simulator for interferometric SAR

In this paper, we present a time-domain (TD) raw signal simulator for an interferometric synthetic aperture radar (SAR). We consider the case of a spaceborne SAR operating in stripmap, spotlight, and hybrid modes, but the case of an airborne SAR can be considered as well. The spaceborne platform is considered as traveling on its nominal (Keplerian) orbit, and the targets are located on an ellipsoidal earth. We describe an accurate TD simulator, highlighting its usefulness in studying the effects on the SAR impulse response and on images from targets with limited extension due to operational conditions different from the nominal one.

Potentials and Limitations of Moon-Borne SAR Imaging

Moon exploitation is among the next space mission priorities. Earth observation (EO), which is traditionally implemented on artificial lower Earth orbit satellites, can be, in principle, extended to the platform constituted by the natural Earth satellite. With this regard, we investigate the features related to the EO by a possible Moon-borne synthetic aperture radar system in terms of imaging characteristics and potential applications, as well as of expected limitations.

Filtering of interferometric SAR phase images as a fuzzy matching-pursuit blind estimation

We present an original application of fuzzy logic to restoration of phase images from interferometric synthetic aperture radar (InSAR), which are affected by zero-mean uncorrelated noise, whose variance depends on the underlying coherence, thereby yielding a nonstationary random noise process. Spatial filtering of the phase noise is recommended, either before phase unwrapping is accomplished, or simultaneously with it. In fact, phase unwrapping basically relies on a smoothness constraint of the phase field, which is severely hampered by the noise. Space-varying linear MMSE estimation is stated as a problem of matching pursuit, in which the estimator is obtained as an expansion in series of a finite number of prototype estimators, fitting the spatial features of the different statistical classes encountered, for example, fringes and steep slope areas. Such estimators are calculated in a fuzzy fashion through an automatic training procedure. The space-varying coefficients of the expansion are stated as degrees of fuzzy membership of a pixel to each of the estimators. Neither a priori knowledge on the noise variance is required nor particular signal and noise models are assumed. Filtering performances on simulated phase images show a steady SNR improvement over conventional box filtering. Applications of the proposed filter to interferometric phase images demonstrate a superior ability of restoring fringes yet preserving their discontinuities, together with an effective noise smoothing performance, irrespective of locally varying coherence characteristics.

Comparison between different types of green's function factorization for the BMIA/AIM method

Three different formulations that allow to extend the BMIA/AIM method to the analysis of large dielectric stratified structures are introduced. These techniques lead to an approximate form of the multilayer Greens function, valid in the region where the thickness of the substrate can be considered small compared to its transverse dimension. This approximate form results as the product of three terms: two dependent by the source and observation longitudinal position, the other by its transverse distance. The first technique makes use of a suitable description of the Greens function in terms of discrete complex images. The remaining ones deal with the evaluation of the Greens function along the steepest descent path integration and a least-squares interpolation formulation, respectively.

COSMO/SkyMed AO projects - advanced 2D and 3D Focusing of COSMO/SkyMed SAR data

We present a research project, funded by the Italian Space Agency (ASI), aimed at performing 2D and 3D Focusing of COSMO/SkyMed (CSK) SAR Data. We describe the main objectives of the project, briefly illustrate employed techniques, and finally present the obtained results. The latter show that sub-meter resolution can be achieved in the enhanced spotlight CSK acquisition mode, and that by using 3D focusing it is possible to resolve scatterers at different slant heights within the same range-azimuth resolution cell, even in areas characterized by severe height discontinuities and large thermal dilations effects.

A modification of the canonical grid series expansion in order to increase the efficiency of the SMCG method

In this letter, we present a Greens function approximation valid in the weak-interaction region that can be used with the sparse-matrix canonical grid (SMCG) method. It can be easily introduced into existing SMCG codes, allowing a reduction in size of the neighborhood region and, consequently, of the dynamic memory and the computation time requirements.

An iterative method to improve phase unwrapping of noisy interferograms

Extraction of topographic Digital Elevation Model (DEM) by interferometric data requires the recovering of an interferometric phase absolute value from its principal value (measured). This is carried out by appropriate algorithms called phase unwrapping algorithms. The authors propose a phase unwrapping algorithm that estimates phase gradient by a multiresolution approach and computes the final interferometric phase by an iterative process. Several examples show that only a few iterative steps are enough to reach the maximum performance with respect to algorithms that compute absolute interferometric phase value directly from a gradient estimate.

Discovery of Electromagnetic Waves and Their Impact on Our Life-Style

The history of discovery of electromagnetic waves and its impact on our life style is presented in the framework of its historical context. Discovery of the relevant equations by James Clerk Maxwell are first commented, and the subsequent applications discussed: wired transmission of electric power, cable transmission of messages via telegraph and telephone, up to wireless propagation over the ground and via satellites. More recent preliminary experiments of wireless power transmission are also noted. We conclude with a conjecture about possible additional impacts of Maxwell’s discovery on the organization of our society.

A Radar Eye on the Moon: Potentials and Limitations for Earth Imaging

Among the next space missions goals the exploitation of the Moon, the natural Earth satellite, is gaining an increasing interest. Colonization of the Moon is along the usual track of human civilization and economic expansion; it is also related to a large number of scientiflc issues, including Earth Observation (EO). With respect to standard LEO satellite commonly used in remote sensing, Moon has speciflc features. In this work we analyze the potentials as well as the limitations related to active microwave remote sensing with Synthetic Aperture Radar in terms of imaging characteristics and potential applications.

Raw/SLC signal simulator for spaceborne interferometric SAR systems

(Interferometric) SAR signal simulation is very useful to test processing algorithms of real data. A simulator can provide a reliable version of signals received by a particular system, when the geometric and the electromagnetics characteristics of targets are fixed. The authors present a simulator for an interferometric (single-pass) SAR system placed on a spaceborne platform moving over an ideal Keplers orbit. Stripmap and spotlight operational mode can be considered, and, by describing system geometry in a platform frame of reference, mechanical deformation of structures can be easily modeled.