Opportunistic radar imaging using a multichannel receiver

Bistatic Synthetic Aperture Radars have a physically separated transmitter and receiver where one or both are moving. Besides the advantages of reduced procurement and maintenance costs, the receiving system can sense passively while remaining covert which offers obvious tactical advantages. In this work, spaceborne monostatic SARs are used as emitters of opportunity with a stationary ground-based receiver. The imaging mode of SAR systems over land is usually a wide-swath mode such as ScanSAR or TOPSAR in which the antenna scans the area of interest in range to image a larger swath at the expense of degraded cross-range resolution compared to the conventional stripmap mode. In the bistatic geometry considered here, the signals from the sidelobes of the scanning beams illuminating the adjacent sub-swath are exploited to produce images with high cross-range resolution from data obtained from a SAR system operating in wide-swath mode. To achieve this, the SAR inverse problem is rigorously formulated and solved using a Maximum A Posteriori estimation method providing enhanced cross-range resolution compared to that obtained by classical burst-mode SAR processing. This dramatically increases the number of useful images that can be produced using emitters of opportunity. Signals from any radar satellite in the receiving band of the receiver can be used, thus further decreasing the revisit time of the area of interest. As a comparison, a compressive sensing-based method is critically analysed and proves more sensitive to off-grid targets and only suited to sparse scene. The novel SAR imaging method is demonstrated using simulated data and real measurements from C-band satellites such as RADARSAT-2 and ESA’s satellites ERS-2, ENVISAT and Sentinel-1A. In addition, this thesis analyses the main technological issues in bistatic SAR such as the azimuth-variant characteristic of bistatic data and the effect of imperfect synchronisation between the non-cooperative transmitter and the receiver

Passive Synthetic Aperture Radar Imaging Using Commercial OFDM Communication Networks

Modern communication systems provide myriad opportunities for passive radar applications. OFDM is a popular waveform used widely in wireless communication networks today. Understanding the structure of these networks becomes critical in future passive radar systems design and concept development. This research develops collection and signal processing models to produce passive SAR ground images using OFDM communication networks. The OFDM-based WiMAX network is selected as a relevant example and is evaluated as a viable source for radar ground imaging. The monostatic and bistatic phase history models for OFDM are derived and validated with experimental single dimensional data. An airborne passive collection model is defined and signal processing approaches are proposed providing practical solutions to passive SAR imaging scenarios. Finally, experimental SAR images using general OFDM and WiMAX waveforms are shown to validate the overarching signal processing concept

Active and Passive Multi-Sensor Radar Imaging Techniques Exploiting Spatial Diversity

The work here presented reports several innovative SAR and ISAR radar imaging techniques exploiting the spatial diversity offered by multi-sensor systems in order to improve the performance with respect to the conventional, single channel cases. Both the cases of dedicated transmitters and exploitation of opportunity transmitters are considered

Active and Passive Multi-Sensor Radar Imaging Techniques Exploiting Spatial Diversity

The work here presented reports several innovative SAR and ISAR radar imaging techniques exploiting the spatial diversity offered by multi-sensor systems in order to improve the performance with respect to the conventional, single channel cases. Both the cases of dedicated transmitters and exploitation of opportunity transmitters are considered

Project ORION: Orbital Debris Removal Using Ground-Based Sensors and Lasers

About 100,000 pieces of 1 to 10-cm debris in low-Earth orbit are too small to track reliably but large enough to cripple or destroy spacecraft. The ORION team studied the feasibility of removing the debris with ground-based laser impulses. Photoablation experiments were surveyed and applied to likely debris materials. Laser intensities needed for debris orbit modification call for pulses on the order of lOkJ or continuous wave lasers on the order of 1 MW. Adaptive optics are necessary to correct for atmospheric turbulence. Wavelength and pulse duration windows were found that limit beam degradation due to nonlinear atmospheric processes. Debris can be detected and located to within about 10 microrads with existing radar and passive optical technology. Fine targeting would be accomplished with laser illumination, which might also be used for detection. Bistatic detection with communications satellites may also be possible. We recommend that existing technology be used to demonstrate the concept at a loss of about $20 million. We calculate that an installation to clear altitudes up to 800 km of 1 to 10-cm debris over 2 years of operation would cost about$80 million. Clearing altitudes up to 1,500 km would take about 3 years and cost about $160 million

Conference on Spacecraft Reconnaissance of Asteroid and Comet Interiors : January 8-10, 2015, Tempe, Arizona

The goal of AstroRecon is to identify and evaluate the best technologies for spacecraft robotic reconnaissance of comets, asteroids, and small moons--paving the way for advanced science missions, exploration, sample return, in situ resource utilization, hazard mitigation, and human visitation.Shell GameChanger, ASU NewSpace, The Johns Hopkins University Applied Physics Laboratoryinstitutional support Arizona State University, Lunar and Planetary Institute, National Aeronautics and Space Administration, Universities Space Research Association Arizona State University's Students for the Exploration and Development of Space ; sponsors Shell GameChanger, ASU NewSpace, The Johns Hopkins University Applied Physics Laboratory ; conveners Erik Asphaug Arizona State University, Tempe, Jekan Thangavelautham Arizona State University, Tempe ; program committee Erik Asphaug (Co-chair Science) Arizona State University, Tempe [and 6 others].PARTIAL CONTENTS: Human Exploration / P. A. Abell and A. S. Rivkin--Comet Radar Explorer / E. Asphaug--Development of Communication Technologies and Architectural Concepts for Interplanetary Small Satellite Communications / A. B. Babuscia and K. C. Cheung--Numerical Simulations of Spacecraft-Regolith Interactions on Asteroids / R.-L. Ballouz, D. C. Richardson, P. Michel, and S. R. Schwartz--Kuiper: A Discover, Class Observatory for Outer Solar System Giant Planets, Satellites, and Small Bodies / J. F. Bell, N. M. Schneider, M. E. Brown, J. T. Clarke, B. T. Greenhagen, R. M.C. Lopes, A. R. Hendrix, and M. H. Wong--Landing on Small Bodies: From the Rosetta Lander to MASCOT and Beyond / J. Biele, S. Ulamec, P.-W. Bousquet, P. Gaudon, K. Geurts, T.-M. Ho, C. Krause, R. Willnecker, and M. Deleuze--High-Resolution Bistatic Radar Imaging in Support of Asteroid and Comet Spacecraft Missions / M. W. Busch, L. A. M. Benner, M. A. Slade, L. Teitelbaum, M. Brozovic, M. C. Nolan, P. A. Taylor, F. Ghigo, and J. Ford--Asteroid Comet and Surface Gravimetric Surveying can Reveal Interior Structural Details / K. A. Carroll