SISAR imaging for space debris based on nanosatellites

The increasing amount of space debris poses a growing challenge in the development of space travel. In previous work, a proposed system comprising of a low budget space-borne passive radar based on CubeSAT, flying in Low Earth Orbit (LEO), demonstrated promising results in terms of space debris detection performance. In this work, a novel shadow inverse synthetic aperture radar (SISAR) model for space debris imaging based on nanosatellite is presented. An analysis of the received forward scattering signal is provided along with a novel model for moving transmitters and receivers SISAR imaging. Using simulated data and assuming different scenarios, the performance of the new algorithm is assessed; wherein, a classification scheme is applied using the output of the SISAR algorithm for classification between simple target shapes

Target shadow profile reconstruction in forward scatter radar

This thesis is dedicated to the matter of imaging (further explained as profile reconstruction) in Forward Scatter Radars (FSR). Firstly, an introduction to radar systems, including forward scatter radar, is made, then an introduction to the scalar theory of diffraction and principles of holography follows. The application of holographic imaging principles in the microwave domain is studied. The practical modelling of forward scatter radar target signals is made, based on the theoretical expectations and approximations outlined. Theoretical background of the imaging in FSR is made, based on previously published work. A novel approach for profile reconstruction is introduced based on the practices of holographic imaging, together with simulated results. Experimental set-ups used in the feasibility proof are described and experimental results are presented for 8 different targets in both a single-node and multistatic configurations. Preliminary accuracy analysis of these reconstructed target profiles is done, outlining practical application issues and domain of accuracy. Quantitative measures of the accuracy of the reconstructed images are defined

High resolution radargrammetry with COSMO-SkyMed, TerraSAR-X and RADARSAT-2 imagery: development and implementation of an image orientation model for Digital Surface Model generation

Digital Surface and Terrain Models (DSM/DTM) have large relevance in several territorial applications, such as topographic mapping, monitoring engineering, geology, security, land planning and management of Earth's resources. The satellite remote sensing data offer the opportunity to have continuous observation of Earth's surface for territorial application, with short acquisition and revisit times. Meeting these requirements, the SAR (Synthetic Aperture Radar) high resolution satellite imagery could offer night-and-day and all-weather functionality (clouds, haze and rain penetration). Two different methods may be used in order to generate DSMs from SAR data: the interferometric and the radargrammetric approaches. The radargrammetry uses only the intensity information of the SAR images and reconstructs the 3D information starting from a couple of images similarly to photogrammetry. Radargrammetric DSM extraction procedure consists of two basic steps: the stereo pair orientation and the image matching for the automatic detection of homologous points. The goal of this work is the definition and the implementation of a geometric model in order to orientate SAR imagery in zero Doppler geometry. The radargrammetric model implemented in SISAR (Software per Immagini Satellitari ad Alta Risoluzione - developed at the Geodesy and Geomatic Division - University of Rome "La Sapienza") is based on the equation of radar target acquisition and zero Doppler focalization Moreover a tool for the SAR Rational Polynomial Coefficients (RPCs) generation has been implemented in SISAR software, similarly to the one already developed for the optical sensors. The possibility to generate SAR RPCs starting from a radargrammetric model sounds of particular interest since, at present, the most part of SAR imagery is not supplied with RPCs, although the RPFs model is available in several commercial software. Only RADARSAT-2 data are supplied with vendors RPCs. To test the effectiveness of the implemented RPCs generation tool and the SISAR radargrammetric orientation model the reference results were computed: the stereo pairs were orientated with the two model. The tests were carried out on several test site using COSMO-SkyMed, TerraSAR-X and RADARSAT-2 data. Moreover, to evaluate the advantages and the different accuracy between the orientation models computed without GCPs and the orientation model with GCPs a Monte Carlo test was computed. At last, to define the real effectiveness of radargrammetric technique for DSM extraction and to compare the radrgrammetric tool implemented in a commercial software PCI-Geomatica v. 2012 and SISAR software, the images acquired on Beauport test site were used for DSM extraction. It is important underline that several test were computed. Part of this tests were carried out under the supervision of Prof. Thierry Toutin at CCRS (Canada Centre of Remote Sensing) where the PCI-Geomatica orientation model was developed, in order to check the better parameters solution to extract radargrammetric DSMs. In conclusion, the results obtained are representative of the geometric potentialities of SAR stereo pairs as regards 3D surface reconstruction

A Review of Ground Target Detection and Classification Techniques in Forward Scattering Radars

This paper presents a review of target detection and classification in forward scattering radar (FSR) which is a special state of bistatic radars, designed to detect and track moving targets in the narrow region along the transmitter-receiver base line. FSR has advantages and incredible features over other types of radar configurations. All previous studies proved that FSR can be used as an alternative system for ground target detection and classification. The radar and FSR fundamentals were addressed and classification algorithms and techniques were debated. On the other hand, the current and future applications and the limitations of FSR were discussed

Ricerche di Geomatica 2011

Questo volume raccoglie gli articoli che hanno partecipato al Premio AUTeC 2011. Il premio è stato istituito nel 2005. Viene conferito ogni anno ad una tesi di Dottorato giudicata particolarmente significativa sui temi di pertinenza del SSD ICAR/06 (Topografia e Cartografia) nei diversi Dottorati attivi in Italia

STRATHcube : the design of a CubeSat for space debris detection using in-orbit passive bistatic radar

There is a growing need to detect, track and catalogue space debris in the congested Low Earth Orbit (LEO) region. A method to detect debris could be to use space-based passive bistatic radar (PBR). The STRATHcube project proposes to launch a CubeSat into LEO as a PBR technology demonstrator where a signal processing algorithm developed at the University of Strathclyde to detect space debris will be tested. The concept involves a radar receiver and antenna on-board a CubeSat orbiting at a low altitude to detect the radio signals transmitted by operational satellites orbiting at higher altitudes. These signals may have been modified by an object orbiting between the operational satellites and the CubeSat and therefore would indicate a piece of debris exists. This paper will present the integration of PBR technology onto a CubeSat as a payload on the STRATHcube mission and discuss the challenges faced due to the limitations of the small platform. The use of a custom-built 3D antenna and an off-the-shelf patch antenna are investigated as design options for the payload. A high-level design for each option was completed to evaluate their capabilities on the size of trackable debris and to determine their mass and power parameters. After an extensive trade-off analysis at a system level, carried out to narrow down the options of the PBR payload on the CubeSat platform, it was determined that the patch antenna option presented the best way of facilitating the experiment onboard the CubeSat due to its small size and mass. The completed design of the STRATHcube mission will enable an in-orbit demonstration of the PBR technology, which if successful, will provide an alternative to conventional ground-based tracking that is cheaper and more available to the space community. This method would then be proven to industry who can use this approach to implement on a larger scale in the future

Advanced signal processing techniques for WiFi-based Passive Radar for short-range surveillance

In this work, advanced signal processing techniques for a Passive Radar (PR) based on WiFi transmissions are considered. The possibility to exploit such a ubiquitous and accessible source is shown to be an appropriate choice for the detection, localization and imaging of vehicles, people and aircrafts within short ranges in both outdoor and indoor environments

Forward scatter radar meets satellite : passive sensing of aerial target using satellite communication waveforms

The problem of single-channel reception of global positioning system (GPS) communication waveforms makes passive sensing of aerial target difficult because of forward scatter. This paper proposes a novel aerial target passive sensing method based on linear canonical transformation (LCT) using the forward scattered satellite communication waveforms. The proposed method firstly preprocesses the received signal based on the characteristics of the traditional satellite tracking loop and the forward scattered satellite communication waveforms to effectively suppress the interference of the direct wave through DC removal. Then, the Gaussian noise and multipath interference in the channel are suppressed by applying a rectangular window to its linear canonical domain. Finally, aerial target sensing is performed based on the peak value of signals in the linear canonical transform domain. The characteristic signal is constructed by analyzing the satellite communication waveforms. Combining the linear canonical transform with the matched filter (MF) to estimate the target parameter. Simulation results show that the proposed method can effectively perform the aerial target sensing by using satellite communication waveforms in the forward scatter scenario

Aeronautical Engineering. A continuing bibliography with indexes, supplement 156

This bibliography lists 288 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1982

Co-evolution of Rock Strength, Erosion, and Steep Topography

Rock-mass strength is recognized as an important control in geomorphology that influences the morphology of landscapes and modulates feedbacks between surface processes, tectonics, and climate. Despite this general recognition, many of the factors controlling rock-mass strength in the near-surface are not widely understood, largely due to challenges in quantifying strength over the appropriate spatial scales. Although the strength of small rock samples can be readily measured with laboratory techniques, fractures and weathering gradients at progressively larger spatial scales dramatically reduce the strength of rock masses compared to their intact (unfractured) counterparts. Due to a lack of approaches that incorporate discontinuities into strength estimates, the contribution of rock-mass properties to geomorphic processes and topographic relief remains unquantified. In this dissertation, I address gaps in our understanding of the role of rock mass strength in geomorphology by testing new methods for quantifying scale-dependent rock mass strength, using these new tools to quantify gradients in strength across environmental variables, and assessing the contribution of rock strength to topographic form and erosion. Research activities focus on an inverted sedimentary basin within the Western Transverse Ranges of southern California, USA, where differences in fault activity have exposed sedimentary rocks with variable burial histories. With Chapters 2 and 3, I test new approaches to quantifying outcrop- and hillslope-scale near-surface rock-mass strength using slope-stability models and field methods. With these new techniques, I resolve order-of-magnitude differences in strength that appear to be related to diagenetic changes associated with the maximum burial depth of young clastic sedimentary rocks. I resolve smaller differences in strength (300 kPa – 1.5 MPa) that are positively correlated with mean erosion rates, which I hypothesize reflects decreased weathering extents with increasing erosion rates for mountain ranges experiencing faster fault slip rates. Assessing the contribution of rock-mass properties to the evolution of landscapes requires recognizing patterns of long-term fault activity and erosion. In Chapter 4, I resolve differences in the timing of reverse fault localization, initiation, and propagation, as well as long-term erosion rates, using low-temperature thermochronometry. Inverse thermal modelling of Miocene to Pleistocene apatite (U-Th-Sm)/He cooling ages and partially reset zircon (U-Th)/He cooling ages on eleven vertical transects reveal that deformation localization was likely driven by contrasts in the rheology and strength of the lithosphere, rather than by restraining bend tectonism. With estimates of near-surface rock-mass strength and long-term erosion rates mapped across the landscape in Chapters 2-4, I evaluate the contribution of rock-mass strength to topography in Chapter 5. Where erosion rates and climate are spatially uniform, I find a non-linear relationship between topographic metrics and rock-mass shear strength, implying that rock-mass strength sets the topographic structure of the mountain range. Chapter 6 builds on this observation, and I find that post-wildfire erosion as quantified from repeat airborne-LiDAR surveys is positively correlated with local slope and the strength of the underlying bedrock. Rather than setting the erodibility of earth materials directly, I hypothesize that rock-mass strength controls event-driven erosion by setting the steepness of the overlying landscape. Collectively, interpretations put forward in this dissertation highlight the complex interplay between tectonics, erosion, topography, and the mechanical evolution of rock to transportable, erodible materials.PHDEarth and Environmental SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/169827/1/kirkft_1.pd