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One of the main topics in synthetic aperture radar (SAR) tomography (TomoSAR) is the estimation of the vertical structures’ location, which scatter the field back towards the sensor, constrained to a reduced number of passes. Moreover, the introduction of artifacts and the increase of the ambiguity levels due to irregular sampling, consequence of non-uniform acquisition constellations, complicate the accurate estimation of the source parameters. Pursuing the alleviation of such drawbacks, the use of statistical regularization approaches, based on the maximum-likelihood (ML) estimation theory, has been successfully demonstrated in the previous related studies. However, these techniques are constrained to the assumption that the probability density function (pdf) of the observed data is Gaussian. In this paper, in order to solve the ill-posed non-linear TomoSAR inverse problem, we relax this assumption and apply the weighted covariance fitting (WCF) criterion instead. The latter alleviates the previously mentioned drawbacks, and retrieves a power spectrum pattern (PSP) with an outline more similar to the expected one, i.e., recovered using matched spatial filtering (MSF) with a higher number of tracks. First, we present the mathematical background of the related regularization methods, adapted to solve the TomoSAR inverse problem, from which we derive our novel technique, named WISE (WCF-based Iterative Spectral Estimator). Then, the differences and similarities between the addressed regularization approaches are discussed, besides their main advantages and disadvantages. Finally, the implementation details of WISE are treated, along with simulated examples and experimental results gotten from a forested test site.

The BIOMASS DEM Product Prototype Processor (BIO-DEMPP) is being developed in the frame of ESA's Earth Explorer BIOMASS mission. The prototype includes a complete interferometric SAR chain, from the stack co-registration until the mosaicking of the derived height products (Digital Elevation and Digital Terrain Models). This paper presents an overview of the BIODEMPP architectural design and its validation strategy, as well as first results obtained with simulated BIOMASS-like data.

Synthetic aperture radar (SAR) tomography (TomoSAR) is a remote sensing technique that allows for the 3-D representation of the illuminated areas, recovering the vertical distribution of the backscattered power at each range-azimuth position. In this context, and with the aim of retrieving feature-enhanced tomograms, this paper addresses a new multi-stage iterative method that operates robustly in real-world TomoSAR operating scenarios with irregularly distributed acquisition constellations and only few available looks. The addressed approach alleviates the drawbacks of the conventional matched spatial filter (MSF) technique, which retrieves high ambiguity levels when irregular sampling is considered. Also, it alleviates the drawbacks of the commonly used Capon beamforming technique, which results to be inapplicable when the involved data covariance (structure) matrices are rank deficient. The addressed novel method combines the descriptive experiment design regularization (DEDR) framework for enhanced image reconstruction, with the wavelet domain thresholding (WDT)-based sparsity promoting refinement in the wavelet transform (WT) domain. The capabilities of the addressed WDT-refined virtual adaptive beamforming (VAB) approach, which we refer to as WAVAB, are corroborated via processing P-band airborne TomoSAR data of the German Aerospace Center (DLR), acquired by the E-SAR system over the test site located at the Vindeln municipality, northern Sweden, in 2008.

In this paper data acquired at different frequencies, namely X- and L-band are exploited to perform DInSAR analysis. The objective of this work is to present strategies to apply DInSAR by evaluating the required processing aspects to jointly estimate the deformation for multi-frequency time series. The X-band data are acquired with the TerraSAR-X sensor, while the L-band ones are ALOS/ALOS-2 data. The present work is the result of the ongoing “inter agency arrangement for strategic partnership” between the German Aerospace Center (DLR) and the Japanese Aerospace Exploration Agency (JAXA) concerning Multi-temporal InSAR analysis.

Synthetic aperture radar (SAR) tomography (TomoSAR) employs array signal processing techniques, in order to estimate the location of the vertical structures that compose the backscattering field, in the direction perpendicular to the line-of-sight (PLOS). Due to the limited number of tracks for practical TomoSAR sensing scenarios, it becomes challenging to accurately estimate the source parameters. Additionally, irregular sampling and non-uniform acquisition constellations introduce artifacts and increase ambiguity. The usage of super-resolved parametric methods and compressed sensing (CS) based approaches, improve the vertical resolution and mitigate the effect of sidelobes. However, parametric approaches have the main drawback related to the assumption that the scene is composed by a known finite number of point-type backscattering sources. Also, the CS-based techniques regularly imply a considerable computational burden. Overcoming the disadvantages of the above mentioned TomoSAR-adapted methods, this paper presents a novel non-parametric iterative approach for feature enhanced SAR tomography, in the context of maximum likelihood (ML) estimation theory. The feature enhancing capabilities of the proposed technique are corroborated via processing L-band airborne TomoSAR data of the German Aerospace Center (DLR), acquired by the F-SAR system over the forested test site of Froschham, Germany, in 2017.

Companion SAR missions offer a cost-effective solution to enhance the added value of existing SAR satellites. In particular, they offer new possibilities to extend the observation space and provide one or several single-pass interferometric channels for the acquisitions. The paper aims to provide a description of an end-to-end performance simulation for companion SAR missions, including the evaluation of two exemplary configurations under realistic conditions and with the incorporation of the major error sources affecting these systems. A critical discussion of the results will be included of the final version of the paper drawing from the analysis relevant conclusions for the design of payload and concepts for future companion SAR missions.

The paper critically reviews the limits, for safety-critical automotive applications, of state-of-art technologies for nonvolatile memory data/instruction storage and MEMS inertial sensors. Some hints, supported by theoretical analysis and/or experimental measures, to overcome these issues are provided. The reliability limits of plastic packages, typically adopted to keep low the device cost in the large volume automotive market, are also discussed. By exploiting a Fault Tree Analysis, the packaging bottlenecks are highlighted and proper countermeasures at circuit and technology level are proposed.

This paper provides an overview of the future development of spaceborne SAR systems with multi-baseline imaging capability like polarimetric SAR interferometry (PolInSAR), tomography (TomoSAR) and holography (HoloSAR). The goal is to fill the multi-dimensional data space with additional information from acquisitions having different spatial or temporal baselines. Multi-baseline imaging opens the door for a new class of image products in spaceborne SAR. Well-known examples are across-track and along-track interferometry, which allow the measurement of surface topography, ground deformation, ocean currents as well as glacier movements. While across-track and along-track interferometry are well established techniques and have been widely used by current spaceborne SAR systems, PolInSAR, TomoSAR and HoloSAR are emerging techniques which are shaping the future development of spaceborne SAR. New mission concepts for multi-static SAR configurations with distributed and sparse arrays will pave the way for this development.

Companion SAR missions offer a cost-effective solution to boost the performance and capabilities of existing SAR missions. With the use of companion satellites, a whole suite of coherent single-pass observations become feasible, allowing for the interferometric and tomographic exploitation of the received data. Interferometric and tomographic measurements are however very sensitive to even the slightest degradations in the phase of the received data, and impose stringent requirements on the calibration concept of the mission. Weakly-synchronised companion SAR missions may have significant residual clock errors, which challenge the attainment of this requirements. We put forward an innovative calibration concept based on autonomous (data-based) calibration at different product levels and present an estimation of the expected performance for ESA's SAOCOM/CS mission.

This paper presents results of the Sentinel-1 sensor in the interferometric wide-swath (IW) mode encompassing the first two years of operation of the mission. The paper focuses on persistent scatterer interferometric results and their validation. Further applications and investigations are also addressed, e.g., earthquakes, volcanoes and tomography.

SAR tomography is a remote sensing technique, extending SAR interferometry, that allows three-dimensional imaging of volumetric targets. It allows, for example, to analyse the vertical structure of vegetation layers or other targets with significant penetration of the sensor's radiation (dry soil, ice layers, etc.). The ability to monitor the 3-D inner structure of volumetric targets and to extract information about the nature and location of ongoing scattering processes promises a break-through in key environmental problems. Indeed, structural parameters of volume scatterers in the biosphere and cryosphere, such as vegetation height and moisture content, forest vertical structure and biomass, or snow / ice depth and layering are critical inputs for ecological process modelling and enable effective monitoring of ecosystem change.

In this paper we investigate the surface displacement pattern before and after the 2011 Tohoku earthquake using persistent scatterer interferometry of ALOS/PALSAR and TerraSAR-X images. For confirming the accuracy of the estimated displacement, interferometric phase components were evaluated and simulated data were created. Using the simulated data, the accuracy of filtering methods to mitigate tropospheric methods was evaluated. Real data processing clarified detailed spatial patterns of previously unrecognized displacement. Comparison with GPS data showed that the estimated displacement was within the expected accuracy of the simulated data. Our results demonstrate the effectiveness of the combination of ALOS/PALSAR and TerraSAR-X data analysis, and the accuracy evaluation by quantifying interferometric phase components.

This paper provides a vision for the future development of spaceborne SAR systems with multi-baseline imaging capability like polarimetric SAR interferometry (PolinSAR), tomography (TomoSAR) and holography (HoloSAR). The goal is to fill the multi-dimensional data space with additional information from acquisitions having different spatial or temporal baselines. Multi-baseline imaging opens the door for a new class of image products in spaceborne SAR. Well-known examples are across-track and along-track interferometry, which allow the measurement of surface topography, ground deformation, ocean currents as well as glacier movements. While across-track and along-track interferometry are well established techniques and have been widely used by current spaceborne SAR systems, PolinSAR, TomoSAR and HoloSAR are emerging techniques which are shaping the future development of spaceborne SAR. New mission concepts for multistatic SAR configurations with distributed and sparse arrays will pave the way for this development.

The first commercial thermal scanning probe lithography tool is used for patterning of single- and bi-level surface-relief gratings. A modified tri-layer pattern transfer process is proposed to facilitate the fabrication of bi-level gratings.

A multi-technology platform is considered to interact and cooperate with complex heterogeneous domestic or industrial environments. This way an automatic set up of the digital representation of such spaces is possible, that we shall call smart spaces, in which identifying, localizing, monitoring and updating different real objects is carried out in real time. Natural interaction with tagged and untagged items may then be carried by different users' categories having various needs. This may be accomplished by augmenting the RFID technology with a) direction finding capabilities of a monopulse radar, to remotely discover and select items; b) gesture recognition, to enable the user to interact with the Smart Space and the devices in a natural way; c) computer vision based item recognition, to allow objects themselves to act as natural tags. Interoperability of all these technologies is made possible by a suitable software infrastructure.

The use of polarimetric and interferometric SAR (Pol-InSAR) has been demonstrated to bring significant advantages for several remote sensing applications. Sometimes, the hypothesis that the scattering mechanisms (SM) do not suffer large changes in the two acquisitions is performed (ESM). On the other hand, a different set of algorithms should be employed. In this paper a new methodology is proposed to identify errors consequence of possible changes. The algorithm performs a Lagrange optimization of an error factor of the Pol-InSAR coherences, returning also the SM that change maximally and minimally during the two acquisitions. The algorithm was tested on E-SAR L-band data acquired during the AgriSAR 2006 campaign.

This document presents and discusses the financing strategies for the McGill Nanotools Microfab.

In recent years, three-dimensional imaging by means of SAR tomography has become a field of intensive research. In SAR tomography, the vertical reflectivity function for every azimuth-range pixel is usually recovered by processing data collected using a defined repeat pass acquisition geometry. The most common approach is to generate a synthetic aperture in the elevation direction through imaging from a large number of parallel tracks. This imaging technique is appealing, since it is very simple. However, it has the drawback that large temporal baselines, which is the case for space-borne platforms, can severely affect the reconstruction. In an attempt to reduce the number of parallel tracks, we propose a new tomographic focusing approach that trades number of SAR images for correlations between neighboring azimuth-range pixels and polarimetric channels. As a matter of fact, this can be done under the framework of Distributed Compressed Sensing (DCS), which stems from Compressed Sensing (CS) theory, thus also exploiting sparsity in our tomographic signal. In addition, we address the problem of measurements affected by additive as well as multiplicative speckle noise. Results demonstrating the potential of the DCS methodology will be validated by using fully polarimetric L-band data acquired by the E-SAR sensor of DLR.

TanDEM-X is a high-resolution interferometric mission with the main goal of providing a global and unprecedentedly accurate digital elevation model (DEM) of the Earth surface by means of single-pass X-band SAR interferometry. Despite its usual quasi-monostatic configuration, TanDEM-X is the first genuinely bistatic SAR system in space. During its monostatic commissioning phase, the system has been mainly operated in pursuit monostatic mode. However, some pioneering bistatic SAR experiments with both satellites commanded in non-nominal modes have been conducted with the main purpose of testing the performance of both space and ground segments in very demanding scenarios. In particular, this paper reports about the first bistatic acquisition and the first single-pass interferometric (mono/bistatic) acquisition with TanDEM-X. Even in the absence of essential synchronisation and calibration information, bistatic images and interferogramswith similar quality to pursuit monostatic have been obtained.

The study of data acquired over a circular trajectory has raised an increasing interest in the SAR community. Two main reasons summarize the interest in such geometry. First, sub-wavelength resolution can be achieved, as the targets in the spotted area are observed under a 360o aperture. Second, the use of the information from different azimuthal directions allows one to obtain information of the scene in the third dimension, making possible a 3D target reconstruction. In any case, both applications require certain target reflectivity homogeneity. This paper shows several processing results and analyzes the potentials and limitations of circular SAR to perform tomography of semi-transparent media. Special processing aspects, like the estimation of residual motion errors due to inaccuracies in the navigation data, are also addressed. Data acquired at L-band by DLR's E-SAR system are used to demonstrate the high resolution and tomographic imaging capabilities of circular SAR. The results include the tomogram of a Luneburg lens, as well as preliminary results over man-made targets and vegetation.

A piezoresistive readout method for MEMS torsional resonators is presented. To this purpose, a new theoretical model describing the piezoresistive effects on monocrystalline and polycrystalline beams, used as suspended resistors, is investigated. A square law, linking the angular displacement thetas to the resistance variation DeltaR, is derived. The theory is confirmed by ANSYS FE (finite element) simulations. When adding a feedback to an actuator, a piezoresistive sensing part can read the output signal without increasing the process complexity and represents an alternative to capacitive sensing. A measurement configuration, based on a Wheatstone bridge, as well as an implementation of this measurement scheme to silicon-germanium (SiGe) resonators are also proposed.

The main drawback of SAR Tomography (SARTom) is the considerable number of tracks required to achieve the 3-dimensional (3D) representation of a viewed scene. The key point concerns the trade-off between the vertical resolution and the control on ambiguities phenomena. This paper deals with the problem of the determination of the minimum number of required tracks when super-resolution subspace methods are applied. The results are validated on real data acquired in L-band by the E-SAR system of the German Aerospace Centre.

During recent years the experimental SAR (E-SAR) system of the German Aerospace Center (DLR) has continuously been operated to acquire data for different scientific applications in forestry, agriculture and glaciology. In this context, the data where mainly used to develop new scattering models in preparation of future space-borne missions posing increasing accuracy requirements especially for the processing of repeat-pass interferometric data. Also direct model-free methods like differential SAR interferometry for measuring displacements in the order of the wavelength or SAR tomography for real 3D microwave imaging of scattering volumes determined the development of advanced and very accurate motion compensation techniques. This paper first gives an overview of the updates of the E-SAR system performed during the last couple of years and then focusses on the recently developed airborne interferometric processing methods and their applications.

The aim of this work is to exploit the MUSIC algorithm performance in order to enhance target separability in range and azimuth, i.e. achieve point targets separation inside a resolution cell. Simulations have been done in order to plan and check the feasibility of a super-resolution experiment that took place in September 2006 on the test site of Oberpfaffenhofen (Germany). The data set has been acquired with the E-SAR system of the DLR in X-band. The targets to be separated were seven small corner reflectors that have been placed in a way that their response falls in one or, at maximum, two resolution cells of the standard Fourier SAR image. A post-processing implementation of the MUSIC algorithm has been proposed allowing, in the already focused SAR image, to retrieve the targets geometry. Conditions and analysis of the results have been carried out.

SAR tomography (SARTom) is an imaging technique that allows multiple phase centers separation in the vertical (height) direction. It is performed after standard 2D SAR repeat-pass processing and operates on a stack of coregistered SAR images. Theoretically, the coregistration between two images is height dependent and the use of a reference height (or a DEM) is needed, although not ideal in the case of volumetric target (multiple phase centers in one resolution cell). In this paper, the drawbacks related to the choice of this reference in a tomographic context are analysed and a height dependent coregistration approach is proposed. In order to do this, it is also necessary to remove processing corrections related to the reference height, such as motion compensation, and make them height dependent. The inclusion of the height dependency during the tomographic SAR processing results in a better quality of the final tomograms in terms of pseudo-power and phase centers separation. The results of the proposed approach are validated on real data acquired by the E-SAR system of the German Aerospace Centre - DLR.

An innovative JFET bio-transistor, based on a metal oxide (MOX) nanowire bundle, was developed in order to electrically detect biological binding. The working principle of this device relies on modulation of a MOX space charge region (SCR), acting as the channel of a field effect transistor, instead of an enriched/depleted Si channel like in chem.-FETs. The feasibility was at first demonstrated by the development of a bio-sensor made of an SnO2 thin film derivatized with oligodeoxyribonucleotide-probes. We implemented a protocol to immobilize single strands of nucleic acid over SnO2 and developed a system for electrical sensing of hybridization in liquid solution. The same protocol was then applied on a SnO2 nanowire bundle, synthesized by thermal evaporation of oxide powders under controlled conditions with the presence of Pt catalyst. The results obtained on a group of nanowires suggest the possibility -now under development -to produce nano-bio-transistors based on single nanowires of metal oxides.

APSFET (adsorption porous silicon FET) is a porous silicon-based device constituted of a FET structure with a porous adsorbing layer between drain and source. Adsorbed gas molecules in the porous layer induce an inverted channel in the crystalline silicon under the porous silicon itself. The mobile charge per unit area in the channel depends on the molecular concentration in the sensing layer, so that adsorbed gas plays a role similar to the charge on the gate of a FET. NO/sub 2/ detection using the APSFET is demonstrated for the first time. NO/sub 2/ concentration as low as 100 ppb was detected. Unfortunately, such high sensitivity is obtained only for fresh APSFET samples, due to a drift of sensor properties with sample aging. A low thermal oxidation was performed on fresh samples in order to passivate the porous silicon surface. The oxidation step positively affects the sensor in term of stability of electrical performance, keeping the high response. to nitrogen dioxide.

We report on the innovative electrical detection of biological binding, based on a thin metal oxide (MOX) film as channel for a field effect transistor. The working principle relies on modulation of a MOX space charge region (SCR) instead of an enriched/depleted Si channel like in chem-FETs. The feasibility of the working principle was at first demonstrated by pH measurement in liquid. Afterwards we implemented a reliable protocol for the immobilization of ODNs and for the electrical detection of their hybridization. Work is in progress to scale MOX down to nanosized nanowire.

A vapour phase polymerization technique of pyrrole (Py) is presented. A saline compound, obtained by a selective oxy-chloridization procedure of Cu thin layer on glass and quartz electrodized substrates, has been used as oxydant to grow thin patterned films of polypyrrole (PPy) to electrically interconnect Au electrodes. This technique could be utilized for the realization of molecular electronic devices in which the PPy patterns do not depend on the electrode array geometry, but only upon the salt, and hence the Cu coating, geometry. upper metallic layer can be chemically trasformed in a salt which acts as an oxydant for Py polymerization. The aim of this work is to obtain PPy thin layers on electrodized substrates with well .defined patterns, able to interact with Ab/Ag immunoenzymatic complexes for the realization of moleculartransistor-based immunosensors. We describe here the process which has been implemented for selective oxy-chloridization of Cu on Au layers. In addition we report results on both salt and PPy analysis, together with VISNIR absorption spectra and PPy electrical characterization. EQUIPMENT