New SAR Target Imaging Algorithm based on Oblique Projection for Clutter Reduction

International audienceWe have developed a new Synthetic Aperture Radar (SAR) algorithm based on physical models for the detection of a Man-Made Target (MMT) embedded in strong clutter (trunks in a forest). The physical models for the MMT and the clutter are represented by low-rank subspaces and are based on scattering and polarimetric properties. Our SAR algorithm applies the oblique projection of the received signal along the clutter subspace onto the target subspace. We compute its statistical performance in terms of probabilities of detection and false alarms. The performances of the proposed SAR algorithm are improved compared to those obtained with existing SAR algorithms: the MMT detection is greatly improved and the clutter is rejected. We also studied the robustness of our new SAR algorithm to interference modeling errors. Results on real FoPen (Foliage Penetration) data showed the usefulness of this approach

Multidimensional Low-Rank Filter based on the AU-HOSVD for MIMO STAP

International audienceWe propose in this paper a new low rank filter for MIMO STAP (Multiple Input Multiple Output Space Time Adaptive Processing) based on the AU-HOSVD (Alternative Unfolding Higher Order Singular Value Decomposition). This decomposition called the AU-HOSVD is able to process data in correlated dimensions which is desirable for STAP methods. We apply the new filter to MIMO STAP simulated data. The results are encouraging and outperforms the conventional STAP 2D filter in terms of number of secondary data

SETHI / RAMSES-NG: New performances of the flexible multi-spectral airborne remote sensing research platform

International audienceSETHI is an airborne SAR/GMTI system developed by the French Aerospace Lab. ONERA, and integrating various sensors. In 2016 ONERA invested in upgrade and improvement of all SETHI components. The microwave ones cover from VHF-UHF to X Band, full polarimetric and very high resolution, along track and cross track interferometry and very high precision multi-baseline capacity for interferometry and tomography applications. The optronic sensors offer very high spatial resolution visible images and fine spectral scene analysis in VNIR and SWIR bands. This paper presents the upgrade and new performances of this flexible platform and the qualification campaign results with various sensor configurations

Algorithmes d’imagerie SAR polarimétrique basés sur des modèles à sous-espace.: Application à la détection de cible sous couvert forestier.

This thesis deals with the development of new SAR processors for detection of targets under foliage. For this application, classical SAR images are very noisy; the target has a low response and there are a lot of false alarms due to the interferences which are mainly the trunks of the forest. To detect target and reduce interferences, we reconsider the way processing a SAR image by using models which take into account the scattering properties of the target and the interferences. These models are developed for signals in sigle polarisation and in double polarisation (HH and VV) and are defined with low-rank subspaces generated from the responses of canonical elements. From this modeling, we develop new SAR processors. First, we focus on the detection of the target and on the reduction of false alarms. The performances of these processors in terms of detection and false alarms reduction are evaluated with realistic simulated data and we emphasize on the interest of using a polimetric information. We also apply these algorithms to real data that allows us to analyze the images in real-life context.Cette thèse porte sur le développement de nouveaux processeurs SAR pour la détection de cibles sous le feuillage. Pour cette application, les images SAR classiques sont très bruitées; la cible a une réponse faible et il y a beaucoup de fausses alarmes dues aux interférences qui sont principalement les troncs de la forêt. Pour détecter la cible et de réduire les interférences, nous reprenons le traitement d'une image SAR en utilisant des modèles qui prennent en compte les propriétés de diffusion de la cible et les interférences. Ces modèles sont développés pour les signaux en polarisation simple (HH ou VV) et en double polarisation (HH et VV). Ils sont définis avec des sous-espaces de rang faible générés à partir des réponses des éléments canoniques et nous pouvons en déduire de nouveaux processeurs SAR. Les performances de ces processeurs en termes de détection et de réduction des fausses alarmes sont évaluées avec des données simulées réalistes et nous illustrons l'intérêt d'utiliser l'information polarimétrique. Nous appliquons également ces algorithmes à des données ONERA aéroportées qui nous permettent d'analyser les images dans un contexte réel

Algorithmes d'imagerie SAR polarimétriques basés sur des modèles à sous-espace (application à la détection de cible sous couvert forestier)

Cette thèse traite du développement de nouveaux algorithmes de formation d'image SAR dédiés à la détection de cible sous couvert forestier. Pour cette application, l'imagerie SAR classique produit des images fortement bruitées dans lesquelles la cible a une réponse faible et les interférences, principalement les trocs des arbres, provoquent de nombreuses fausses alarmes. Pour pouvoir augmenter la détection de la cible et réduire les interférences, nous reconsidérons le principe de formation d'image SAR en utilisant des modèles qui prennent en compte les priorités de diffusion de la cible et des interférences. Ces modèles sont développés pour des signaux en simple polarisation et en double polarisation (HH et VV) et sont définis par des sous-espaces de rangs faibles générés à partir des réponses d'éléments canoniques. A partir de ces modélisations, nous développons de nouveaux algorithmes d'imagerie SAR. Nous nous concentrons d'abord sur la détection de la cible puis sur la réduction des interférences. Les performances de ces algorithmes en termes de détection et de réductions des fausses alarmes sont évaluées sur des données simulées mais réalistes et nous insistons l'apport de l'information polarimétrique pour l'amélioration de celles-ci. Nous appliquons également nous algorithmes sur des données réelles qui nous permettent d'analyser les images obtenues dans un cadre réel.This thesis deals with the development of new SAR processors for detection of targats under foliage. For this application, classical SAR images are very noisy; the target has a low response and there are a lot of false alarms due to the interferences which are mainly the trunks of the forest. To detect target and reduce interferences, we reconsider the way processing a SAR image by using models which take into account the scattering properties of the target and the interferences. These models are developed for signals in sigle polarisation and in double polarisation (HH and VV) and are defined with low-rank subspaces generated from the responses of canonical elements. From this modeling, we develop new SAR processors. First, we focus on the detection of the target and on the reduction of false alarms. The performances of these processors in terms of detection and false alarms reduction are evaluated with realistic simulated data and we emphasize on the interest of using a polimetric information. We also apply these algorithms to real data that allows us to analyze the images in real-life context.NANTERRE-BU PARIS10 (920502102) / SudocSudocFranceF

Reduced rank STAP techniques for MIMO

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Analysis and Comparison of MIMO Radar Waveforms

International audienceChoosing a proper waveform is a critical task for the implementation of multiple-input multiple-output (MIMO) radars. In addition to the general requirements for radar waveforms such as good resolution, low sidelobes, etc, MIMO radar waveforms also should possess good orthogonality. In this paper we give a brief overview of MIMO radar waveforms, which are classified into four categories: (1) time division multiple access (TDMA), (2) frequency division multiple access (FDMA), (3) Doppler division multiple access (DDMA), and (4) code division multiple access (CDMA). A special circulating MIMO waveform is also addressed The properties as well as application limitations of different waveforms are analyzed and compared. Some simulations results are also presented to illustrate the respective performance of different waveforms

Airborne MIMO investigation for STAP-GMTI applications

International audienceGround moving target indicator (GMTI) radar performance is strongly depending on the antenna geometry: length of the equivalent radar aperture (longer apertures enable lower minimum detectable velocity-MDV) and sparsity. Compact and sparse multiple-input multiple-output (MIMO) techniques have been investigated into this paper to point out potential benefits compared to SIMO configuration. In 2016 an experiment was conducted with ONERA BUSARD motoglider to collect MIMO GMTI dataset on instrumented ground vehicles. DDMA waveform has been operated as orthogonal pattern on transmit. Analysis of the data indicates improved clutter nulling and resulting MDV with the MIMO techniques compared to the conventional SIMO one

New Low-Rank Filters for MIMO-STAP based on an Orthogonal Tensorial Decomposition

International audienceWe develop in this paper a new adaptive LR filter for MIMO-STAP application based on a tensorial modelling of the data. This filter is based on an extension of the HOSVD (which is also one possible extension of SVD to the tensor case), called AU-HOSVD, which allows to consider the combinations of dimensions. This property is necessary to keep the advantages of the STAP and the MIMO characteristics of the data. We show that the choice of a good partition (as well as the tensorial modelling) is not heuristic but have to follow several features. Thanks to the derivation of the theoretical formulation of multimode ranks for all partitions, the tensorial LR filters are easy to compute. Results on simulated data show the good performance of the AU-HOSVD LR filters in terms of secondary data and clutter notch