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D'Aria D.,ARESYS | Ferretti A.,Tele Rilevamento Europa TRE | Ferretti A.,TRE Canada Inc. | Guarnieri A.M.,ARESYS | And 2 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

We propose a calibration method suitable for a set of repeated synthetic aperture radar (SAR) acquisitions that uses both absolute calibrated devices (such as corner reflectors) and stable targets identified in the scene [the permanent scatterers (PSs)]. Precisely, the role of the PS is to extend the initial calibration sequence by monitoring the radiometric stability of the system throughout the whole mission life span. At a first step, this paper approaches the problem of PS-based normalization by an iterative maximum-likelihood method that exploits the stack of complex interferometric SAR images. Two solutions are given based on different assumptions on the PS phases. As a second step, the merging of these estimates with the available calibration information is discussed. Results achieved by experimental acquisitions are shown in two different SAR systems: 1) a C-band spaceborne SAR and 2) a Ku-band ground-based SAR. © 2009 IEEE.

Belotti M.,Polytechnic of Milan | D'Aria D.,Aresys | Guccione P.,Polytechnic of Bari | Miranda N.,European Space Agency | And 2 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

This paper proposes a set of tests that provide necessary and, as far as possible, sufficient conditions for verifying the phase preservation of synthetic aperture radar (SAR) processors. This paper discusses two different test families composed of self-consistency and point-Target-based tests. The set of self-consistent tests extends the well-known CEOS-OFFSET to very different acquisition modes, namely, StripMAP, ScanSAR, TopSAR, and SPOTLIGHT, and introduces a new complementary test to check the consistency of the space-variant implementation of a processor. The set of point target tests, based on the analysis of point target simulated data, completes the self-consistent tests by providing a verification of phase accuracy between different bursts and swaths. © 1980-2012 IEEE.

Belotti M.,Polytechnic of Milan | D'Aria D.,Aresys | Iannini L.,Polytechnic of Milan | Guarnieri A.M.,Polytechnic of Milan | Scirpoli S.,Polytechnic of Milan
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2011

The aim of this paper is the definition of a series of quantitative phase preserving tests that would be a necessary tool to evaluate the performance of different focusing algorithms and to define some necessary conditions to validate their efficacy and precision. The tests have been thought and defined to form a general tool that can cope with a wide number of systems and acquisition geometries. © 2011 IEEE.

Recchia A.,Aresys | Giudici D.,Aresys | Miranda N.,Earth Observation Directorate | Monti Guarnieri A.,Polytechnic of Milan
European Space Agency, (Special Publication) ESA SP | Year: 2016

A technique for the calibration of the pointing of a SAR sensor from the Doppler Centroid estimates over still land is presented. The technique is validated over real Sentine-1 data and results of the sensor calibration are provided. Finally a possible application of the technique to geophysical parameters retrieval is described.

Giudici D.,Aresys | Piantanida R.,Aresys | Rocca F.,Polytechnic of Milan | Monti Guarnieri A.,Polytechnic of Milan | Recchia A.,Aresys
European Space Agency, (Special Publication) ESA SP | Year: 2016

The paper introduces a technique for the enhanced processing of TOPSAR data. It is based on repeated passes of the sensor over the same area and is aimed at obtaining "enhanced resolution" images of coherent scatterers in the scene by combining two "de-synchronized" acquisitions, useless for interferometric purposes. The paper introduces the STAGTOPS concept and provides a first demonstration exploiting a couple of 12 days apart Sentinel-1A TOPSAR IW images with a synchronization issue. The proposed technique could be further tested by exploiting the novel Sentinel-1B sensor (launch 25th April 2016), reducing the revisit time to 6 days.

Bienati N.,ENI S.p.A | Mazzucchelli P.,Aresys | Codazzi M.,ENI S.p.A
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

3D multiple elimination plays a fundamental role in marine data processing. 3D SRME algorithm has some manifest advantages with respect to other multiple elimination techniques: in particular its accuracy and its fully data-driven nature that allows the application in the early stages of processing propose it as the benchmark for surface related multiple estimation and elimination. In this abstract we address the problem of the automatic optimization of SRME operator aperture. We exploit the valuable information hidden in the Multiple Contribution Gather to define the summation area that contains the Downward Reflection Points for the different multiple generators. The computation of 3D stacking volumes allows to remove some of the aliasing artifacts that contaminate the estimated multiples. Moreover, as a pleasant side-effect, the overall computational cost of 3D SRME task can be lowered by carefully exploiting this technique. Results on a 3D narrow azimuth dataset prove the correctness and feasibility of the proposed approach.

Costagliola S.,Aresys | Mazzucchelli P.,Aresys | Bienati N.,ENI S.p.A
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

In this paper we outline a new method to improve the solution of the filter set estimation problem applied to the separation of two interfering wave-fields. The problem is well described in [Guitton, 2005] where the two data components are assumed to be non-Gaussian and the cost function is minimized by using a Hybrid L1/L2 norm. Another kind of hybrid-norm solver has been derived in [Costagliola et al, 2011]. Here we want to extend the latter by introducing an uncorrelation assumption. Our aim is to use this tool to better separate the fullwavefield starting from a preliminary estimation of its components. The problem can be casted as the minimization over the set of Stiefel matrices and it can be solved by SVD decomposition (plus additional iterations in a gradient based algorithm if the set is orthogonal but not necessary orthonormal). However, this procedure is not only non-linear and non-convex, but also numerically expensive. Thus, we reformulate the problem as a constrained optimization solved by a gradient based method that searches for the solution in the neighborhood of the unconstrained optimization solution. Results on synthetic and field data show that introducing orthogonality constraints can improve the wavefield component separation.

Adamo A.,ARESYS | Mazzucchelli P.,ARESYS | Bienati N.,ENI S.p.A
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014

Radon transforms are integral operators widely used in seismic exploration for multiple attenuation, velocity analysis and data interpolation. A reasonable assumption about the Radon transform applied to seismic images is sparseness, where the image energy focuses into clusters in the Radon model space. In this paper we apply the Weak Orthogonal Matching Pursuit framework (WOMP) to exploit sparseness and implement a High Resolution Radon Transform: in particular, we introduce a new automatic selection criterion for the Weak Orthogonal Matching Pursuit algorithm based on the physical model underlying the problem (called GeOMP). Results on real data prove the effectiveness of the method over general purpose selection criteria in terms of both reconstruction quality and decreased computational cost.

Fioretti L.,Aresys | Mazzucchelli P.,Aresys | Bienati N.,ENI S.p.A
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2015

Recently, technical results from the theory of Compressive Sensing have been applied to the Fourier class of algorithms for solving the ever-increasing seismic data interpolation problem while handling potentially irregularly sampled geometries. The method we here propose makes use of the so-called Conjugate Gradient Pursuit with the Stagewise Selection Strategy, a novel general purpose algorithm for sparse representation, which brings advantages in terms of computational costs when compared to the well-known Matching Pursuit, while not affecting accuracy. The effectiveness and efficiency of the derived interpolation method is proved and compared to the performances of the Matching Pursuit-based interpolation method when applied on a real dataset showing, in turns, intrinsic sampling irregularity and heavy manual trace decimation. © 2015 IEEE.

Scagliola M.,Aresys | Fornari M.,European Space Agency | Tagliani N.,Aresys
IEEE Geoscience and Remote Sensing Letters | Year: 2015

This letter describes a novel approach to retrieve the pitch of the CryoSat satellite by the analysis of Synthetic Interferometric Radar ALtimeter (SIRAL) acquisitions in synthetic aperture radar (SAR) or SAR-interferometric mode over ocean. The power distribution of the single-look echoes, which are gathered for each sample location on the Earth surface, has been verified to be modulated by the along-track antenna pattern. Thus, the actual antenna pointing direction can be retrieved by fitting the model of the along-track antenna pattern on the power distribution of a stack, which is a collection of single-look echoes referred to the same ground location but acquired from different look angles. With the pitch measurement being independent of the attitude information returned by the onboard star trackers, by comparison of the pitch measured from data and of the pitch from the star tracker, the existence of a bias on the pitch can be verified. Exploiting the proposed approach, the pitch returned by star trackers on CryoSat has been found to be biased by about 0.0533°, confirming similar results obtained by other methods proposed in the literature. It is worth noticing that the method for pitch estimation here described is not limited to CryoSat but can be applied to any SAR altimeter without loss of generality. © 2004-2012 IEEE.

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