Hélène Oriot

The French Aerospace Lab ONERA | ONERA · DEMR - Department of Electromagnetism and Radar

The electromagnetic congestion due to the continuous growth of spectral demand has been skyrocketing for the past years. Joint radar-communication systems are thus attracting attention as they can alleviate the spectrum occupancy by using the same bandwidth to perform both applications. In this context, a cooperative radar-communication system, whi...

Joint radar-communication systems are attracting attention as they can alleviate the frequency spectrum by utilizing the same bandwidth. To design such systems, continuous phase frequency-shift keying codes are chosen, in order to transmit information and generate high-resolution images. However, such codes require sidelobe energy mitigation which...

p>The electromagnetic congestion due to the continuous growth of spectral demand has been skyrocketing for the past years. Joint radar-communication systems are thus attracting attention as they can alleviate the spectrum occupancy by using the same bandwidth to perform both applications. In this context, a cooperative radar-communication system, w...

p>The electromagnetic congestion due to the continuous growth of spectral demand has been skyrocketing for the past years. Joint radar-communication systems are thus attracting attention as they can alleviate the spectrum occupancy by using the same bandwidth to perform both applications. In this context, a cooperative radar-communication system, w...

SAR (Synthetic Aperture Radar) tomography reconstructs 3-D volumes from stacks of SAR images. High-resolution satellites such as TerraSAR-X provide images that can be combined to produce 3-D models. In urban areas, sparsity priors are generally enforced during the tomographic inversion process in order to retrieve the location of scatterers seen wi...

On 30 September 2017, an Air France Airbus A380-800 suffered a failure of its fourth engine while over Greenland. This failure resulted in the loss of the engine fan hub, fan blades and surrounding structure. An initial search recovered 30 pieces of light debris, but the primary part of interest, a ~220 kg titanium fan hub, was not recovered becaus...

SAR (Synthetic Aperture Radar) tomography reconstructs 3-D volumes from stacks of SAR images. High resolution satellites such as TerraSAR-X provide images that can be combined to produce 3-D models. In urban areas, sparsity priors are generally enforced during the tomographic inversion process in order to retrieve the location of scatterers seen wi...

The resolution achieved by current synthetic aperture radar (SAR) sensors provides a detailed visualization of urban areas. Spaceborne sensors such as TerraSAR-X can be used to analyze large areas at a very high resolution. In addition, repeated passes of the satellite give access to temporal and interferometric information on the scene. Because of...

When using STAP on (range, Doppler) high resolution SAR images to detect moving targets, strong scatterers (corner reflectors, double bounces) tend to be detected as moving targets. In this paper, a method to discriminate strong scatterers from an actual moving target is presented. It uses the fact that on a SAR image, a moving target appears at a...

In this paper, the problem of estimating complex-valued proportional covariance matrices is addressed. The obtained estimate generalizes the Fixed Point Estimate to scaled packets of data, and is hence called the Generalized Fixed Point Estimate (GFPE). The statistical properties (bias, consistency, asymptotical distributions) of the estimate are p...

When using multichannel synthetic aperture radar (MSAR) to perform moving target detection, the coherence between the received signals is closely linked to the detection capacities of the system. In airborne MSAR context, because of the platform movement, the antenna patterns, as well as the phase shifts between the channels, evolve in different wa...

In this paper, the problem of proportional covariance matrices estimation for random Gaussian complex vectors is investigated. The maximum likelihood estimates of the matrix and the scale factors are derived, and their statistical performances are studied, through bias, consistency and asymptotic distribution. It is also shown that the problem trea...

Synthetic aperture radar (SAR) has become an important technique for generating high-resolution images of the ground because of its all-weather capabilities. SAR imaging of stationary scenes is nowadays well mastered. Moving targets induce a delocalization and a defocusing effect in the azimuth direction in a SAR image. This latter effect can be us...

The principal instrument of the NASA/CNES wide-swath altimetry mission Surface Water and Ocean Topography (SWOT) is the Ka-band Radar Interferometer (KaRIn), a bistatic synthetic aperture radar (SAR) system operating on near-nadir swaths on both sides of the satellite track. There are limited reports on backscattering from natural surfaces at this...

In order to support SWOT and future altimetry space missions at Ka-band, an airborne measurement campaign has been done by ONERA. A large Ka band radar dataset has been recorded and processed, leading to backscattering measurements over different kinds of water surfaces, and with different wind regimes. For the first time at this frequency band and...

The TropiSAR campaign has been conducted in August 2009 in French Guiana with the ONERA airborne radar system SETHI. The main objective of this campaign was to collect data to support the Phase A of the 7th Earth Explorer candidate mission, BIOMASS. Several specific questions needed to be addressed to consolidate the mission concept following the P...

Digital elevation model (DEM) extraction in urban areas, using synthetic aperture radar (SAR) imagery, has become a subject of interest with the increased availability of high-resolution SAR images. One of the main advantages of SAR imagery is that, except from very peculiar situations, the radiometry of these images does not depend on weather cond...

Ground moving targets detection and tracking using airborne radar data is a subject of increasing interest. Multiple aperture antenna radars allow detecting and tracking slow targets even in strong clutter environments. On the other hand, high resolution SAR images obtained with one single antenna are of interest for detecting moving targets with a...

We present results from a bistatic SAR experiment conducted with two airborne radars operating in the band 222–460 MHz using HH-polarization. The systems used a step-frequency chirp waveform and were synchronized using GPS 1PPS signals. The processed and analysed data were collected during four flight missions over a test site including forested te...

ONERA, the French Aerospace Lab, has been designing airborne radar for more than two decades for Defence oriented applications, as well as for science applications. In the past six years, the SETHI instrument, hosted on board a Falcon 20 aircraft, has been developed with a main focus on science applications. In this paper, the philosophy of this de...

This paper provides an overview of the airborne SAR systems developed by the French Aerospace Lab ONERA over the past five years. The first system, called SETHI, is presented in the first section. It has been developed according to the standard FAR25 applied to civil application. The main improvement compared to the previous ONERA airborne radar sy...

In order to support future altimetry space missions in Ka-band, an airborne campaign has been realized with the ONERA BUSARD platform and its DRIVE radar. The particularity of this campaign is the line of sight geometry, with very steep incidence angles, using a Ka-band SAR interferometer instrument. The area of interest was the Camargue region in...

SETHI: The Flying Lab This paper presents the new-generation test bench SETHI, developed by ONERA, the French Aerospace Lab. SETHI is a medium range platform dedicated to environmental, scientific and security applications. The first part of this paper describes the system architecture, the development state and the future capabilities. A set of re...

During the last years, the interest in maritime surveillance has been growing up, and spaceborne SAR systems may contribute to the improvement of security and safety at sea. As such, to allow observation of non-cooperative boats with revisit times compatible with the objectives of reactivity of maritime surveillance, the solutions proposed by CNES...

Very impressive results of coherent change detection have been presented for the past ten years. Car tracks or even footprints may be seen on the coherence images as demonstrated by Sandia National Labs with Ka SAR images. Usually these results come from prepared experiments during which all changes are monitored. On the other hand, it has been sho...

The TropiSAR campaign has been conducted in August 2009 in French Guiana with the ONERA airborne system SETHI. The main objective of this campaign was to collect data to support the Phase A of the Earth Explorer candidate mission, Biomass. Several specific questions need to be addressed to answer the recommendations of the ESAC group and the data c...

Building extraction using SAR imagery has been a subject of interest since the availability of high resolution SAR images. In 2008, a new method of DEM extraction using circular imagery has been proposed. This paper uses the main ideas of "Bolter, Reconstruction of man-made objects from high-resolution SAR images", and gives a deeper insight of how...

The TropiSAR campaign has been conducted in August 2009 in French Guiana with the ONERA airborne system SETHI. The main objective of this campaign was to collect data to support the Phase A of the Earth Explorer candidate mission, Biomass. Several specific questions need to be addressed to answer the recommendations of the ESAC group and the data c...

The SETHI sensor from ONERA is an airborne radar equipped with difierent bands (UHF-VHF, L, X) on a Falcon 20. The UHF-VHF band is fully polarimetric and can operate between 225MHz up to 460MHz. In August 2009, this system was used in French Guiana for the TROPISAR experiment. Data were acquired from 0 - incidence angle up to 65 - incidence angle a...

SETHI is the airborne SAR system developed by the ONERA, the French Aerospace Lab dedicated to civilian application. This new SAR system was designed to explore the science applications of radar remote sensing; it can operate over a wide range of frequency bands (X, L and UHF/VHF) and it has polarimetric and interferometric capabilities. In this pa...

This paper provides an overview of the new airborne SAR system developed by the French Aerospace Lab ONERA over the last three years. This system, called SETHI, was developed according to the standard FAR25 applied to civil application. The main improvement compared to the previous ONERA airborne radar system RAMSES is that the antennas are located...

Here are presented issues about building or urban area high resolution imaging using synthetic aperture radar (SAR). Promises of circular imaging are assessed. Indeed, this acquisition mode, though available only to airborne sensors, has the potential to solve shadow and overlay problem through rotation of the slantrange projecting direction. It ha...

This paper presents results obtained during the latest multi-pass interferometric campaign at X-band acquired with the ONERA RAMSES airborne system over several areas. An objective of this campaign is to study the coherent change detection between different acquisitions. There are numerous challenges to achieve thus, specially the multi-date airbor...

Building extraction using SAR imagery has been a subject of interest since the availability of high resolution SAR images. One of the main advantages of this technique is that SAR imagery does not depend on weather conditions. The main drawback is the slant range geometry which leads to large shadow areas, and therefore to incomplete dataset. Autho...

In the field of radar moving target detection, two approaches are usually used: Space Time Adaptive Processing (STAP) which is an optimal solution to point like moving target detections under gaussian clutter hypotheses and Along Track Interferometry (ATI), which is usually dedicated to measuring motion of surface elements (ocean current for instan...

This presentation gives an overview of the latest multi-pass interferometric campaign at X-band acquired with the ONERA RAMSES airborne system over several areas. The thematic of this campaign is interferometric DEM computation using different baseline configurations and change detection. There are numerous challenges to achieve thus, specially the...

The ONERA RAMSES system is a flexible SAR system in constant evolution, developed mainly as a test bench for new technologies and to provide specific data for TDRI (Target Detection, Recognition and Identification) algorithm evaluation. It is flown on a Transall C160 platform operated by the CEV (Centre d'Essais en Vol). This paper presents the mul...

After a first series of full circle SAR acquisitions in L and P-bands during a 2004 joint FOI-ONERA campaign in Sweden, ONERA experimented in 2006 high resolution (15 cm) polarimetric, full circle acquisitions in France and Germany using its X-band sensor. In order to cope with narrower antenna pattern and aircraft attitude fluctuations, a steerabl...

The ONERA RAMSES system is a flexible SAR system in constant evolution, developed mainly as a test bench for new technologies and to provide specific data for TDRI (Target Detection, Recognition and Identification) algorithm evaluation. It is flown on a Transall C160 platform operated by the CEV (Centre d'Essais en Vol). This paper gives an overvie...

Building reconstruction on high resolution X-Band SAR images from a single interferometric view is studied in this paper. The images come from the RAMSES sensor (ONERA). The buildings to reconstruct are supposed to have right-angled footprints and flat or flat by pieces roofs. First, the extraction of features characterizing the building signatures...

The last SAR campaigns of the French ONERA RAMSES system have been dedicated to various applications, military or civilian, including very-high resolution, FOPEN (Foliage penetration) in cooperation with the FOI, MTI, bistatic SAR and vegetation characterization. These different projects gave us the opportunity to improve our SAR processing procedu...

From the recent availability of images recorded by synthetic aperture radar (SAR) airborne systems, automatic results of digital elevation models (DEMs) on urban structures have been published lately. This paper deals with automatic extraction of three-dimensional (3-D) buildings from stereoscopic high-resolution images recorded by the SAR airborne...

The mean shift is a non-parametric algorithm that shifts each sample to the mode of the statistic it belongs to. This filter was originally dedicated to cluster analysis of data and has been recently extended to image processing. In this paper, we are introducing the mean shift algorithm in SAR imagery. It is shown that, after an adapted preprocess...

This paper presents a semi-automatic building extraction method. It is based on active models whose evolution is controled by a surfacic criterion on slices of the correlation cube. The method is first described for a couple of aerial images before tackling satellite images and tri-stereo. Results are shown for Quickbird images.

Three-dimensional models of urban objects are widely used in geographic information systems, telecommunications, or defense applications. The classic technique for obtaining such models is stereoscopy. Images are densely matched, and images of above-ground structures are delineated. We propose two semiautomatic methods based on the Hough transform...

3D modelling of urban objects is widely used for Geographic Information System, telecommunication or defence applications. The most classical technique to obtain such models consists in using several aerial images of the same area. In this paper we propose a new semiautomatic method to delineate buildings which is based on statistical active models...

This paper deals with automatic extraction of 3-D buildings from stereoscopic high-resolution images recorded by the RAMSES sensor. Roofs are not very textured whereas typical strong L-shaped echoes are visible. These returns generally result from dihedral corners between ground and structures. They provide a part of the building footprints and the...

This article deals with Digital Elevation Models (DEM) from airborne stereoscopic SAR images. On our images, roofs are not very textured, dense matching processes cannot manage to restore structure footprints. However, structures can be first extracted from strong echoes from di-hedral corners between ground and structures, by a criterion optimisat...

3D extraction from aerial optical images depends largely on resolution. We are interested in extracting building roofs with metric images. Two steps are described in this paper: image matching and rectangular roof extraction. Once in epipolar geometry, pixels of the two images are matched to obtain a disparity image. On this kind of site, relief di...

This paper deals with automatic extraction of 3-D buildings from stereoscopic high-resolution images recorded by the RAMSES sensor. Roofs are not very textured whereas typical strong L-shaped echoes are visible. These returns generally result from dihedral corners between ground and structures. They provide a part of the building footprints and the...

It is well known that a SAR image is composed of two types of information: amplitude and phase. Nevertheless, the information contained in the phase is hardly exploited on its own. Indeed, the number of processes at work and the scale difference between the image resolution and the wavelength induce, with regard to the phase, a quasi-random spatial...

This paper deals with 3D extraction from airborne stereoscopic radar images. First, man-made structures are detected: circular tanks and rectangular buildings. For tanks, an adapted circular Hough transform is compared with a method based on statistical criteria. This method is extended to rectangular buildings. Then, the detected objects are match...

In the state-of-the-art of 3D extraction from SAR images, we can distinguish three main techniques: radarclinometry, interferometry and radargrammetry. Our project is to perform radargrammetry on high-resolution images recorded by the airborne sensor RAMSES designed and operated by ONERA. Such images allow the visualization of infrastructures and u...

In the state-of-the-art of 3D extraction from SAR images, we can distinguish three main techniques: radarclinometry, interferometry and radargrammetry. Our project is to perform radargrammetry on high-resolution images recorded by the airborne sensor RAMSES designed and operated by ONERA. Such images allow the visualization of infrastructures and u...

High resolution digital elevation model (DEM) are used in many applications, including topographic description of the ground (urban, telecommunications...). We consider the derivation of DEMs from two rectified stereoscopic images. This problem can be formulated as a large scale non-convex optimization problem under constraints, where the unknown i...

Digital Elevation Models can be computed from ERS interferometric products. The phase unwrapping step is the main problem of the process. We present a robust-to-noise phase-unwrapping algorithm based on a global analysis of the interferogram. Then, we focus on a technique that eases the phase unwrapping process by using simultaneously several inter...

The use of spaceborne RADAR interferometry has considerably increased since the ERS-1 launch. In this paper we verify the atmospheric refraction hypothesis. We show that the presence of large height variations and a difference of refractive profiles between the two imagings create interferometric artifacts that have to be dealt with in the Digital...

It is well known that a SAR image is composed of two types of information: amplitude and phase. Nevertheless, the information contained in the phase is hardly exploited on its own. Indeed, the number of processes at work and the scale difference between the image resolution and the wavelength induce, with regard to the phase, a quasi-random spatial...