New target detector based on geometrical perturbation filters for polarimetric Synthetic Aperture Radar (POL-SAR)

Synthetic Aperture Radar (SAR) is an active microwave remote sensing system able to acquire high resolution images of the scattering behaviour of an observed scene. The contribution of SAR polarimetry (POLSAR) in detection and classification of objects is described and found to add valuable information compared to previous approaches. In this thesis, a new target detection/classification methodology is developed that makes novel use of the polarimetric information of the backscattered field from a target. The detector is based on a geometrical perturbation filter which correlates the target of interest with its perturbed version. Specifically, the operation is accomplished with a polarimetric coherence representing a weighted and normalised inner product between the target and its perturbed version, where the weights are extracted from the observables. The mathematical formulation is general and can be applied to any deterministic (point) target. However, in this thesis the detection is primarily focused on multiple reflections and oriented dipoles due to their extensive availability in common scenarios. An extensive validation against real data is provided exploiting different datasets. They include one airborne system: E-SAR L-band (DLR, German Aerospace Centre); and three satellite systems: ALOS-PALSAR L-band (JAXA, Japanese Aerospace Exploration Agency), RADARSAT-2 C-band (Canadian Space Agency) and TerraSAR-X X-band (DLR). The attained detection masks reveal significant agreement with the expected results based on the theoretical description. Additionally, a comparison with another widely used detector, the Polarimetric Whitening Filter (PWF) is presented. The methodology proposed in this thesis appears to outperform the PWF in two significant ways: 1) the detector is based on the polarimetric information rather than the amplitude of the return, hence the detection is not restricted to bright targets; 2) the algorithm is able to discriminate among the detected targets (i.e. target recognition)

Remote sensing and electromagnetic modeling applied to weather and forward scatter radar

This dissertation deals with electromagnetic modelling and data analysis, related to radar remote sensing and applied to forward scatter and meteorological polarimetric systems. After an overview of radar fundamentals to introduce the general terminology and concepts, results are presented at the end of each chapter. In this respect, a generalized electromagnetic model is first presented in order to predict the response of forward scatter radars (FSRs) for airtarget surveillance applications in both near-field and far-field regions. The model is discussed for increasing levels of complexity: a simplified near-field model, a near-field receiver model and a near-field receiver and transmitter model. FSR results have been evaluated in terms of the effects of different target electrical sizes and detection distances on the received signal, as well as the impact of the trajectory of the moving objects and compared with a customized implementation of a full-wave numerical tool. Secondly, a new data processing methodology, based on the statistical analysis of ground-clutter echoes and aimed at investigating the monitoring of the weather radar relative calibration, is presented. A preliminary study for an improvement of the ground-clutter calibration technique is formulated using as a permanent scatter analysis (PSA) and applied to real radar scenarios. The weather radar relative calibration has been applied to a dataset collected by a C-band weather radar in southern Italy and an evaluation with statistical score indexes has drawn through the comparison with a deterministic clutter map. The PSA technique has been proposed using a big metallic roof with a periodic mesh grid structure and having a hemispherical shape in the near-field of a polarimetric C-band radar and evaluated also with an ad-hoc numerical implementation of a full-wave solution. Finally, a radar-based snowfall intensity retrieval is investigated at centimeter and millimeter wavelengths (i.e., at X, Ka and W band) using a high-quality database of collocated ground-based precipitation measurements and radar multi-frequency observations. Coefficients for the multifrequency radar snowfall intensity retrieval are empirically derived using multivariate regression techniques and their interpretation is carried out by particle scattering simulations with soft-ice spheroids. For each topic, conclusions are proposed to highlight the goals of the whole work and pave the way for future studies

COMBAT SYSTEMS Volume 1. Sensor Elements Part I. Sensor Functional Characteristics

This document includes: CHAPTER 1. SIGNATURES, OBSERVABLES, & PROPAGATORS. CHAPTER 2. PROPAGATION OF ELECTROMAGNETIC RADIATION. I. – FUNDAMENTAL EFFECTS. CHAPTER 3. PROPAGATION OF ELECTROMAGNETIC RADIATION. II. – WEATHER EFFECTS. CHAPTER 4. PROPAGATION OF ELECTROMAGNETIC RADIATION. III. – REFRACTIVE EFFECTS. CHAPTER 5. PROPAGATION OF ELECTROMAGNETIC RADIATION IV. – OTHER ATMOSPHERIC AND UNDERWATER EFFECTS. CHAPTER 6. PROPAGATION OF ACOUSTIC RADIATION. CHAPTER 7. NUCLEAR RADIATION: ITS ORIGIN AND PROPAGATION. CHAPTER 8. RADIOMETRY, PHOTOMETRY, & RADIOMETRIC ANALYSIS. CHAPTER 9. SENSOR FUNCTIONS. CHAPTER 10. SEARCH. CHAPTER 11. DETECTION. CHAPTER 12. ESTIMATION. CHAPTER 13. MODULATION AND DEMODULATION. CHAPTER 14. IMAGING AND IMAGE-BASED PERCEPTION. CHAPTER 15. TRACKING. APPENDIX A. UNITS, PHYSICAL CONSTANTS, AND USEFUL CONVERSION FACTORS. APPENDIX B. FINITE DIFFERENCE AND FINITE ELEMENT TECHNIQUES. APPENDIX C. PROBABILITY AND STATISTICS. INDEX TO VOLUME 1. Note by author: Note: Boldface entries in the table of contents are not yet completed

A two-orbital quantum gas with tunable interactions

Im letzten Jahrzehnt haben sich Quantengasexperimente als gut kontrollierbare Modellsysteme zur Untersuchung komplexer Fragestellungen aus diversen Bereichen der Physik etabliert. Ultrakalte Quantengase zeichnen sich insbesondere dadurch aus, dass sie einen direkten und experimentell einfach realisierbaren Zugang zu ihrerWechselwirkung bieten. Das gezielte Einstellen der Wechselwirkungsstärke und die Erforschung der daraus resultierenden Aggregatzustände erlaubt es ein tiefes Verständnis der kondensierten Materie zu gewinnen. Insbesondere erdalkaliähnliche Atome wie Ytterbium bieten die Möglichkeit Phänomene der Festkörperphysik zu untersuchen, die durch die Wechselwirkung von Elektronen in verschiedenen Orbitalen oder durch eine größere Rotationssymmetrie des Spins als in gewöhnlichen Spin-1/2 Systemen hervorgerufen werden. Diese Doktorarbeit präsentiert die experimentelle Charakterisierung der Wechselwirkung ultrakalter, fermionischer Ytterbium-Atome (173Yb) in verschiedenen elektronischen Orbitalen. Dabei wird nachgewiesen, dass sich die Wechselwirkungsstärke mit Hilfe eines externen Magnetfeldes, analog zu einer Feshbach-Resonanz bei Alkali-Atomen, einstellen lässt. Bei Ytterbium wird diese Resonanz durch eine starke Spinaustauschwechselwirkung zwischen den verschiedenen Orbitalen hervorgerufen. Der Nachweis der einstellbaren Wechselwirkung erfolgt über Thermalisierungsexperimente in einer harmonischen Falle und mit Hilfe von hochauflösender Spektroskopie in einem dreidimensionalen Gitter. Des Weiteren wird mit Hilfe der neu entdeckten Resonanz zum ersten Mal experimentell ein stark wechselwirkendes Fermigas in verschiedenen Orbitalen erzeugt und spektroskopisch untersucht. Die Möglichkeit, die interorbitale Wechselwirkung direkt zu manipulieren und somit stark wechselwirkende Quantengase zu erzeugen, ebnet den Weg für die Realisierung und Untersuchung neuartiger Aggregatzustände der kondensierten Materie.In the last decade, quantum gas experiments have been established as well-controllable model systems for the investigation of complex problems originating from different fields of physics. Ultracold quantum gases are of particular interest, as they offer a direct and experimentally feasible access to their interaction. The precise control of the interaction and the exploration of resulting phases of matter grants a profound understanding of condensed matter. In particular, alkaline-earth-like atoms, such as ytterbium, allow for an implementation of condensed matter phenomena, arising from the interaction of electrons in different orbitals or exhibiting an enhanced spin rotation symmetry beyond the conventional spin-1/2 case. This thesis is dedicated to the experimental characterisation of the interaction of ultracold fermionic ytterbium atoms (\YbA) in different electronic orbitals. In the course of this thesis, we reveal the tunability of the interaction by means of an external magnetic field, similar to the case of Feshbach resonances in alkali atoms. For ytterbium, the scattering resonance is induced by the strong spin-exchange interaction between the different orbitals. Experimentally, the tunability of the interaction is demonstrated by a thermalisation experiment in a harmonic trap, as well as high-resolution spectroscopy in a three-dimensional lattice. For the first time, by means of an orbital interaction-induced Feshbach resonance, a strongly interacting two-orbital quantum gas is created and spectroscopically characterised. Controlling the interorbital interaction strength and creating strongly interacting two-orbital quantum gases paves the way towards the implementation of new states of condensed matter

Simulating the Diverse Instabilities of Dust in Magnetized Gas

Recently, Squire & Hopkins showed that charged dust grains moving through magnetized gas under the influence of a uniform external force (such as radiation pressure or gravity) are subject to a spectrum of instabilities. Qualitatively distinct instability families are associated with different Alfvén or magnetosonic waves and drift or gyro motion. We present a suite of simulations exploring these instabilities, for grains in a homogeneous medium subject to an external acceleration. We vary parameters such as the ratio of Lorentz-to-drag forces on dust, plasma β, size scale, and acceleration. All regimes studied drive turbulent motions and dust-to-gas fluctuations in the saturated state, rapidly amplify magnetic fields into equipartition with velocity fluctuations, and produce instabilities that persist indefinitely (despite random grain motions). Different parameters produce diverse morphologies and qualitatively different features in dust, but the saturated gas state can be broadly characterized as anisotropic magnetosonic or Alfvénic turbulence. Quasi-linear theory can qualitatively predict the gas turbulent properties. Turbulence grows from small to large scales, and larger scale modes usually drive more vigorous gas turbulence, but dust velocity and density fluctuations are more complicated. In many regimes, dust forms structures (clumps, filaments, sheets) that reach extreme overdensities (up to ≫10⁹ times mean), and exhibit substantial substructure even in nearly incompressible gas. These can be even more prominent at lower dust-to-gas ratios. In other regimes, dust self-excites scattering via magnetic fluctuations that isotropize and amplify dust velocities, producing fast, diffusive dust motions