Christian Barbier

Space-borne radar interferometric mapping of precursory deformations of a dyke collapse, Dead Sea area, Jordan

Satellite radar interferometry provides a technique to monitor a zone involving active salt tectonic phenomena. We detected movements in the Dead Sea area between 1993 and 1999. These preceded the catastrophic collapse (22 March 2000) of a newly built 12 km dyke belonging to the industrial salt evaporation ponds of the Arab Potash Company. Eighteen other dykes are present and still operational in this area of complex seismotectonic and hydrogeological settings. We used differential Synthetic Aperture Radar (SAR) interferometry (DInSAR) to investigate precursory deformations. Analysis of data shows that the collapsed area and its surroundings were in active subsidence at least 7 years before the event (maximum 44 mm in slant range from 16 December 1995 to 11 October 1997). This case emphasizes DInSAR as a tool suitable to identify deformations in such sensitive areas. It should be used at the stage of pre-feasibility studies of major projects and later in their stability monitoring, when required conditions of application are met.

Ab initio calculations of the static electric polarizability of infinite polymer chains

Abstract The results of recent investigations on the potentialities of the Genkin-Mednis approach for calculating the electric polarizability of infinite stereoregular polymers at the ab initio level are reported. The working expressions are deduced and some of the computation implications are exemplified with results obtained in two study cases: the infinite chain of hydrogen molecules and trarns-polyacetylene.

Unimolecular Decay Paths of Electronically Excited Species. V. The A2B1 State of H2CO

The A 2E state of the NH+3 ion is split by a Jahn–Teller interaction. The potential energy surface of the 2A‘ component of state A undergoes a conical intersection with the surface of the ground state. This brings about an ultrafast relaxation channel.

Fusion of multispectral and radar images in the redundant wavelet domain

We propose in this paper an integration method of the radar information in multispectral images without disturbing the spectral content. The main problem is to define a fusion rule that allows to take into account the characteristics of these images. Also, the main purpose of this paper lies in defining a new fusion rule performed in the redundant wavelet domain. This rule is based on the Mahalanobis distance applied on the wavelet coefficients. Instead of comparing coefficient-to- coefficient, the distance-to-distance comparison is performed. In this case the selected coefficient in the fused image will be the one that presents the large distance. This approach is applied to fusing the infrared band of SPOT with, respectively, RADARSAT and ERS images. The results show that spectral information is well preserved and there is a better information on the texture and the area roughness.

Calculations of molecular polarizabilities using the Valence Effective Hamiltonian (VEH) method

In this paper, we investigate the applicability of the Valence Effective Hamiltonian (VEH) method to calculations of theoretical molecular linear polarizabilities by the Sum-Over-States (SOS) methodology. Test calculations are presented on the polyene series. They indicate that the method gives qualitatively the same trends asab initio small basis sets calculations.

Multi-Chromatic Analysis of SAR Images for Coherent Target Detection

This work investigates the possibility of performing target analysis through the Multi-Chromatic Analysis (MCA), a technique that basically explores the information content of sub-band images obtained by processing portions of the range spectrum of a synthetic aperture radar (SAR) image. According to the behavior of the SAR signal at the different sub-bands, MCA allows target classification. Two strategies have been experimented by processing TerraSAR-X images acquired over the Venice Lagoon, Italy: one exploiting the phase of interferometric sub-band pairs, the other using the spectral coherence derived by computing the coherence between sub-band images of a single SAR acquisition. The first approach introduces the concept of frequency-persistent scatterers (FPS), which is complementary to that of the time-persistent scatterers (PS). FPS and PS populations have been derived and analyzed to evaluate the respective characteristics and the physical nature of the targets. Spectral coherence analysis has been applied to vessel detection, according to the property that, in presence of a random distribution of surface scatterers, as for open sea surfaces, spectral coherence is expected to be proportional to sub-band intersection, while in presence of manmade structures it is preserved anyhow. First results show that spectral coherence is well preserved even for very small vessels, and can be used as a complementary information channel to constrain vessel detection in addition to classical Constant False Alarm Rate techniques based on the sole intensity channel.

Wide band SAR sub-band splitting and inter-band coherence measurements

Range resolution of SAR images is determined by transmitted radar signal bandwidth. Most recent SAR sensors use wide band signals in order to achieve metric range resolution, whereas metric azimuth resolution can be achieved in spotlight mode. As an example, ENVISAT ASAR sensor uses a 15-MHz bandwidth chirp whereas TerraSAR-X spotlight mode uses signals having a 150-MHz bandwidth leading to a potentially 10 times higher resolution. One can also take advantage of wide band to split the full band into sub-bands and generate several lower resolution images from a single acquisition, each being centred on slightly different frequencies. These sub-images can then be used in a classical interferometric process to measure inter-band coherence of a given scene. This inter-band coherence reveals scatterers keeping a stable-phase behaviour along with frequency shift. A simple coherence model derived from Zebker model for randomly distributed surface scatterers is proposed. Examples are presented, showing that scatterers can have a behaviour that deviates from the model, leading to a new information channel.

AB INITIO VARIATIONAL CALCULATION OF DYNAMIC POLARIZABILITIES AND HYPERPOLARIZABILITIES. I. POLARIZABILITY AND QUADRATIC HYPERPOLARIZABILITY OF WATER, CARBON MONOXIDE AND HYDROGEN FLUORIDE

Abstract We present the variation–perturbation method for the ab initio calculation of dynamic polarizabilities and quadratic hyperpolarizabilities. After a summary of the general theory, we report test calculations on the water, carbon monoxide and hydrogen fluoride molecules. Excellent agreement with both experimental and accurate ab initio values is reached when an SCF/LCAO/MO calculation in a 6-311++G** basis set is made for generating the singly-excited Slater determinants over which the first-order correction to the wave function is expanded. Dispersion curves are also reported, a distinctive feature of this technique as compared to many computational schemes currently in use.

Split-Band Interferometry-Assisted Phase Unwrapping for the Phase Ambiguities Correction

Split-Band Interferometry (SBInSAR) exploits the large range bandwidth of the new generation of synthetic aperture radar (SAR) sensors to process images at subrange bandwidth. Its application to an interferometric pair leads to several lower resolution interferograms of the same scene with slightly shifted central frequencies. When SBInSAR is applied to frequency-persistent scatterers, the linear trend of the phase through the stack of interferograms can be used to perform absolute and spatially independent phase unwrapping. While the height computation has been the main concern of studies on SBInSAR so far, we propose instead to use it to assist conventional phase unwrapping. During phase unwrapping, phase ambiguities are introduced when parts of the interferogram are separately unwrapped. The proposed method reduces the phase ambiguities so that the phase can be connected between separately unwrapped regions. The approach is tested on a pair of TerraSAR-X spotlight images of Copahue volcano, Argentina. In this framework, we propose two new criteria for the frequency-persistent scatterers detection, based respectively on the standard deviation of the slope of the linear regression and on the phase variance stability, and we compare them to the multifrequency phase error. Both new criteria appear to be more suited to our approach than the multifrequency phase error. We validate the SBInSAR-assisted phase unwrapping method by artificially splitting a continuous phase region into disconnected subzones. Despite the decorrelation and the steep topography affecting the volcanic test region, the expected phase ambiguities are successfully recovered whatever the chosen criterion to detect the frequency-persistent scatterers. Comparing the aspect ratio of the distributions of the computed phase ambiguities, the analysis shows that the phase variance stability is the most efficient criterion to select stable targets and the slope standard deviation gives satisfactory results.

Study of a passive companion microsatellite to the SAOCOM-1B satellite of Argentina, for bistatic and interferometric SAR applications

We report the results of a preparatory study aimed at exploring candidate applications that could benefit from a passive micro-satellite accompanying the L-band SAOCOM-1B satellite of Argentina, and to carry out a limited demonstration, based on data acquired during ESA airborne campaigns, of selected applications. In a first step of the study, the potential applications were identified and prioritized based on the mission context and strategic applications, scientific need, and feasibility. The next step of the study was to carry out some demonstrations using data sets acquired during the BioSAR 2007-2009, TropiSAR 2009 and IceSAR 2007 campaigns. A P-band InSAR digital elevation model was generated from BioSAR 2007 data. Time-series of interferometric coherence maps were obtained as a tool for change detection and monitoring. PolInSAR processing was carried out on BioSAR 2007 and IceSAR data.