Space-surface bistatic synthetic aperture radar with navigation satellite transmissions: a review

ArticleinSciece China. Information Sciences 58(6):1-20 · June 2015with 33 Reads
Abstract
This paper reviews the theory and practice of Space-Surface Bistatic Synthetic Aperture Radar (SS-BSAR) using navigation satellites as transmitters. In recent years, this innovative technology has reached a maturity stage which allows it to be considered for a wide range of applications. The paper covers the fundamental aspects of this technology as a radar system, such as the resolution, power budget and Point Spread Function (PSF) analysis, as well as its signal processing aspects and the state of the art in terms of advanced SAR techniques that it enables. Finally, the theoretical aspects of the paper may be directly transferred to the more generic SS-BSAR concept.
Ad

Do you want to read the rest of this article?

Request full-text
Request Full-text Paper PDF
  • Thesis
    Passive Global Navigation Satellite System (GNSS)-based Synthetic Aperture Radar (SAR), known as GNSS-SAR, is a currently developing passive radar sensing system. As the system works in passive mode, GNSS-SAR is much cheaper with a much smaller size, thus it is more flexible to be installed under many application scenarios. However because of the restriction of GNSS signal bands, the resolution of GNSS-SAR is lower than conventional SAR. Also, the weak reflected GNSS signals is another limitation for the application of GNSS-SAR. Due to the fact that GNSS signals are low Equivalent Isotropically Radiated Power (EIRP) sources, the signal strength after reflection will be very weak. In this study, a new GNSS-SAR imaging algorithm is proposed to improve object detectability under weak reflected signals. Both theoretical analysis and experimental study show that the proposed algorithm can result in obviously enhanced imaging detectability. For instance, using GPS C/A code signal receiver, the proposed algorithm can detect the object with the signal strength as low as -160 dBm, while the conventional algorithm cannot. Meanwhile, computation with the proposed imaging algorithm is significantly more efficient than with conventional GNSS-SAR imaging algorithm. To enhance range resolution, two new range compression algorithms are proposed to reduce the compressed ambiguity of main-lobe due to chip rate of the respective pseudo-random noise (PRN) code, respectively. In first proposed algorithm (see Chapter 4), range compression is carried out by correlating a reflected GNSS intermediate frequency (IF) signal with a synchronized direct GNSS base-band signal at range domain, where the main lobe ambiguity of the compressed pulse is narrowed down. Thereafter, spectrum equalization technique is applied to the compressed results for suppressing side lobes to obtain a final range-compressed signal. In the second proposed algorithm (see Chapter 5), the main-lobe ambiguity of range compressed signal is deduced by applying Diff2 peak extraction method. Both simulation and field experimental results demonstrate that the proposed range compression algorithms contribute to the resolution enhancement very significantly. For example, on the basis of GPS C/A code receiver platform with the IF value 4 MHz and sampling rate 16 MHz, the first proposed algorithm can improve the best attainable range resolution to 40 m level, while the second proposed algorithm can enhance the best attainable range resolution to 36 m level, compared to the best attainable range resolution 171 m provided by conventional range compression algorithm. In contrast with many current GNSS-SAR research works, the major novelty of the proposed range compression algorithms is that range compressed pulse ambiguity caused by PRN code correlation function has been addressed successfully.
  • Article
    Full-text available
    A frequency scaling (FS) imaging algorithm is proposed for spotlight bistatic SAR data processing. Range cell migration correction (RCMC) is realized through phase multiplication. The proposed algorithm is insensitive to the length of the baseline due to the high precision of the point target (PT) spectrum that we are based on. It is capable of handling bistatic SAR data with a large baseline to range ratio. The algorithms suitable for small and high squint angles are both discussed according to whether the range dependence of the second range compression (SRC) can be neglected or not. Simulated experiments validate the effectiveness of the proposed algorithm.
  • Article
    Synthetic aperture radar (SAR), which uses the global navigation satellite system (GNSS) satellites as transmitters (GNSS-based SAR), consists of the GNSS transmitter in orbit and reception equipment near the ground. GNSS-based SAR has widespread applications in the remote sensing domain, including urban area imaging, because of its low cost and ease of deployment. However, due to the limited power and bandwidth of a GNSS transmitter, the area of the acquired image is very small (with a typical value less than 1 km²). This study proposed a new multistatic SAR concept with GNSS transmitters and multiple receiving antennas to achieve the 360° coverage and the potential of larger urban area image acquisition. The system design and architecture theory, including the resolution analysis and topology optimization, were established in detail. A multi-angle imaging experiment based on BeiDou-2 navigation satellites was designed to validate the proposed concept and theory, and the experimental results demonstrated the effectiveness of the proposed concept and theory.
  • Article
    This paper proposed a 3-D surface deformation retrieval algorithm for synthetic aperture radar interferometry (InSAR) based on a Global Navigation Satellite System (GNSS) as a transmitter and a fixed receiver (GNSS-based InSAR), where simultaneous multiple GNSS transmitters and a repeat-pass concept were adopted. This paper consists of three parts. First, the interferometric phase model under repeat-pass concept was established for both general and bistatic permanent scatterer (PS) cases in the GNSS-based InSAR. Second, the 3-D deformation retrieval algorithm was presented, and the position dilution of precision was analytically derived to evaluate the performance of measured 3-D deformation. Third, using a designed transponder onboard displacement device as the bistatic PS, the feasibility of 3-D deformation retrieval using GNSS-based InSAR was confirmed by repeat-pass experiments, where four simultaneously available Beidou-2 Inclined Geosynchronous Orbit satellites were used as transmitters, and 16 repeat-pass data sets were collected. Using the proposed algorithm, the final experimental results suggested that the GNSS-based InSAR could obtain deformation estimations with better accuracy than at 5 mm in all three directions. Thus, huge potential exists for applications such as landslide prediction and infrastructure safety monitoring.
  • Article
    This paper is a first introduction to the concept of using Global Navigation Satellite Systems (GNSS) as illuminators of opportunity in a passive bistatic real-time radar system for maritime target indication applications. An overview of the system concept and the signal processing algorithms for Moving Target Indication (MTI) is provided. To verify the feasibility of the system implementation as well as test the developed signal processing algorithms, an experimental test bed was developed and the appropriate experimental campaign with the new Galileo satellites and a ferry as the target was carried out. The results confirm the system concept and its potential for multi-static operation, with the ferry being detected simultaneously by two satellites. IEEE
  • Article
    This article deals with the large problem of interferometric synthetic aperture. Our analysis begins with the study of transverse distance influence and the orientation of the interferometric baseline. The processing of elevation problem solving relative to the horizontal resolution of conventional synthetic aperture radar has been carried out, including its ambiguity to choose the optimum parameters of the interferometer and thus improve the surface topography. We found out indeed that when we take a picture of the earth's surface at an angle of inclination of the baseline α=π/4, the best results are obtained.
  • Article
    Full-text available
    The International GNSS Service (IGS) is an international activity involving more than 200 participating organisations in over 80 countries with a track record of one and a half decades of successful operations. The IGS is a service of the International Association of Geodesy (IAG). It primarily supports scientific research based on highly precise and accurate Earth observations using the technologies of Global Navigation Satellite Systems (GNSS), primarily the US Global Positioning System (GPS). The mission of the IGS is “to provide the highest-quality GNSS data and products in support of the terrestrial reference frame, Earth rotation, Earth observation and research, positioning, navigation and timing and other applications that benefit society”. The IGS will continue to support the IAG’s initiative to coordinate cross-technique global geodesy for the next decade, via the development of the Global Geodetic Observing System (GGOS), which focuses on the needs of global geodesy at the mm-level. IGS activities are fundamental to scientific disciplines related to climate, weather, sea level change, and space weather. The IGS also supports many other applications, including precise navigation, machine automation, and surveying and mapping. This article discusses the IGS Strategic Plan and future directions of the globally-coordinated ~400 station IGS network, tracking data and information products, and outlines the scope of a few of its numerous working groups and pilot projects as the world anticipates a truly multi-system GNSS in the coming decade.
  • Bistatic radar experiment
    • D Martinsek
    • R Goldstein
    Martinsek D, Goldstein R. Bistatic radar experiment. In: Proceedings of European Conference on Synthetic Aperture Radar (EUSAR), Friedrichshafen, 1998. 31–34
  • Bistatic synthetic aperture radar using GNSS as transmitters of opportunity. Dissertation for the Doctoral Degree
    • R Zuo
    Zuo R. Bistatic synthetic aperture radar using GNSS as transmitters of opportunity. Dissertation for the Doctoral Degree. Birmingham: University of Birmingham, 2012
  • Multi-angle BiSAR images enhancement and scatting characteristics analysis
    • T Zeng
    • D Ao
    • C Hu
    Zeng T, Ao D, Hu C, et al. Multi-angle BiSAR images enhancement and scatting characteristics analysis. In: Proceedings of International Conference on Radar, Lille, 2014. 1–5
    • J S Subirana
    • J J Zornoza
    • M H Pajares
    Subirana J S, Zornoza J J, Pajares M H. GNSS signal. Navipedia, 2011
  • Book
    The impact of bistatic radar technology on remote sensing is increasing as bistatic systems cross the theoretical threshold into practical embodiment. The wide spectrum of radar applications, including space exploration, defence, transport, aerospace, and meteorology, provides persistent impetus for this progress. This book is dedicated to the more advanced studies in bistatic radar which are currently the subject of intensive research activity and development. With contributions from the leading experts in the field of bistatic radar research, this book collates the latest developments in the field focusing particularly on bistatic synthetic aperture radar (BSAR) and passive bistatic radar systems (PBRS). Within these two areas the text: addresses the main BSAR topologies: spaceborne BSAR, airborne BSAR and space-surface BSAR; analyses the resurgent interest in, and practical applications of, PBRS; introduces passive BSAR technology; covers research of systems used in aircraft detection and tracking, and passive radar remote sensing of the ionosphere and the upper atmosphere. Bistatic Radar: Emerging Technology is an invaluable resource for practising engineers and researchers involved in the design and implementation of advanced bistatic radar systems in aerospace, communications, defence, transport and meteorology. Following on from Bistatic Radar: Principles and Practice it is also a comprehensive reference on the latest research for postgraduate students taking specialist courses in radar technology.
  • Article
    This paper presents preliminary experimental results on passive bistatic SAR imagery acquired at multiple bistatic geometries. Images were obtained using a Space-Surface bistatic SAR topology, with navigation satellites as transmitters of opportunity and a fixed receiver. Details of the experimental program are given and the obtained bistatic images are presented and analyzed. It is demonstrated that diverse scattering effects can be seen for the same scene objects, when viewed from different angles. Such information could potentially be used to increase the amount of information for a given scene.
  • Article
    In BiSAR (Bistatic SAR), scattering characteristic of target varies with the geometric configuration of transmitter and receiver. Single angle SAR image can only provide limited information of a target, which hinders the recognition of targets and limits the application of BiSAR images. To overcome this shortage, a multi-angle fusion method is proposed. Sixteen SS-BiSAR (Space-Surface BiSAR) images using Compass-2/Beidou-2 as opportunity illuminator in different azimuth and elevation angles are obtained via Back-Projection algorithm. Then a fusion image is gained through non-coherent superposition. The result of fusion image shows that: multi-angle fusion is able to capture specular reflection of targets. Structure characteristics of targets are observed in fusion image while in single angle image only a part of target structure is visible. By multi-angle fusion, a continuous outline of target is achieved, which is very advantageous to interpretation of BiSAR images.
  • Article
    This paper presents proof-of-concept methods and results on a passive synthetic aperture radar for surface change monitoring. The bistatic topology comprises navigation satellites (such as Global Positioning System, GLObal Navigation Satellite System (GLONASS), Galileo, or Beidou) as transmitters of opportunity and a fixed receiver on the ground. Surface monitoring is to be provided through coherent change detection. An experimental test bed built to confirm the concept of the system is described, and the appropriate experimental program is presented. Preliminary signal processing algorithms for change detection are derived. Experimentally measured changes are compared to the theoretical predictions, and the obtained results are discussed.
  • Article
    Full-text available
    This letter presents an analysis of the multistatic point-spread function (MPSF) for passive synthetic aperture radar (SAR) with navigation satellites as opportunity transmitters and a stationary receiver. It is shown that a noncoherent combination of bistatic SAR images, obtained by multiple, spatially separated satellites, can yield multistatic imagery that may be essentially improved in terms of resolution when compared with a single bistatic SAR image. The MPSF is derived analytically, for an arbitrary number of bistatic acquisitions and for any bistatic topologies. Analytical results are confirmed using both simulated and experimental data. The obtained result could be applied for the analysis of spatial resolution in multistatic real time radar, thus enabling the adaptive selection of the more suitable opportunity transmitters.
  • Article
    Full-text available
    This paper analyzes the spatial decorrelation between repeat-pass bistatic synthetic aperture radar (BSAR) images with Global Navigation Satellite Systems as transmitters and a fixed receiver. This study is needed in the development of such a system to monitor temporal changes in a scene. The main challenge is that, in this bistatic configuration, spatial coherence heavily depends on the data acquisition geometry. The appropriate theoretical framework to describe spatial coherence for this case is developed by extending well-established monostatic models and, in principle, can be applied to any fixed-receiver BSAR with a spaceborne transmitter. Theoretical results are initially supported by Monte Carlo simulations. Finally, the validity of the model is confirmed by comparing real images.
  • Article
    This paper presents a performance analysis of spaceborne bistatic Synthetic Aperture Radar (SAR) for Earth observation. Since a bistatic system requires the simultaneous use of two spatially separated antennae, this paper refers to the European Space Agency ENVISAT-1 ASAR as the master mission, i.e. reflected echoes collected by ASAR are gathered also by a receiving-only slave antenna, which is on board a small satellite. Depending on orbit configuration, two mission profiles could be envisaged: two satellites flying along parallel orbits with different ascending nodes, or in one orbit plane with adequate angular separation. It is assumed that ENVISAT-1 is non-cooperative; therefore, signal synchronization and swath overlap and antenna separation control are committed to receiving-only spacecraft. To gain further insight into system geometric and radiometric characteristics and accuracy, several simulations are performed by using a computer code, which accounts for spacecraft orbit and attitude dynamics, sensor pointing geometry and Earth rotation. Numerical results and plots show the potentiality of the system for quite accurate three-dimensional measurements. In particular, thanks to system geometry, it is possible to compute target position and slant range components of velocity. Finally, further potential applications are outlined, also considering additional spin-offs for the master mission.
  • Conference Paper
    This paper reports progress and results in the development of a coherent change detector using passive bistatic SAR. The bistatic topology is Space-Surface Bistatic SAR with Global Navigation Satellite Systems as transmitters of opportunity and a fixed receiver. An experimental test-bed, built to test the feasibility of such a system, is described. Current signal processing algorithms measuring surface change are conceptually explained and the obtained experimental results are presented.
  • Conference Paper
    This paper reports progress and results in the development of a coherent change detector using passive bistatic SAR. The bistatic topology is Space-Surface Bistatic SAR with Global Navigation Satellite Systems as transmitters of opportunity and a fixed receiver. An experimental test-bed, built to test the feasibility of such a system, is described. Current signal processing algorithms measuring surface change are conceptually explained and the obtained experimental results are presented.
  • Article
    This study discusses experimental methods and results on passive bistatic synthetic aperture radar using navigation satellites as transmitters of opportunity and a moving receiver. The article highlights practical issues in imaging. Experimental imagery obtained using Galileo satellite emissions and a receiver onboard a ground moving vehicle confirm the system technical feasibility as well as some of its major theoretically predicted parameters.
  • Article
    This paper proposes a method of focusing the bistatic synthetic aperture radar (SAR) (BiSAR) data in spaceborne/stationary configuration. The key problem for imaging is the space variance of Doppler phase. The stationary platform induces additional and different range offsets to the range migration of targets. It causes targets with the same Doppler history, which are determined only by the moving platform, to shift into different bistatic range cells in the echo data. Therefore, the processing is not the same as monostatic SAR imaging which can be fast performed by the uniform matched-filter function in the frequency domain. In this paper, a modified nonlinear chirp scaling (NLCS) algorithm based on series reversion is formulated, which could achieve different range cell migration correction and the equalization of effective range and azimuth frequency modulation rates. The proposed algorithm is validated by simulated and real BiSAR data. In the spaceborne/stationary BiSAR experiment, the YaoGan-1 (an L-band spaceborne SAR system launched by China) is selected as the transmitter, and the stationary receiver is mounted on top of a tall building. The results show that modified NLCS algorithm can effectively focus BiSAR data with serious space variance in spaceborne/stationary configuration.
  • Article
    This paper proposes an extended nonlinear chirp scaling (CS) image formation algorithm for the bistatic synthetic aperture radar systems with the squinted transmitter and a fixed receiver. Since the transmitter with the squint mode was adopted in the system, two main problems, i.e., the spatial variance of the frequency-modulation rate and cubic phase terms, were introduced in the image formation algorithm. The former problem was solved by the linearity approximation of parameter p and deduced q (the second- and third-order coefficients of CS factors in range, which could be used to remove the spatial variation and high-order phase in the range direction) along the range domain while the latter one was compensated by a cubic analytical phase term in the frequency domain. A corresponding experimental hardware system and the bistatic experiments were also described in this paper. Both the simulation and experimental results validated the proposed algorithm.
  • Article
    This paper is concerned with the processing of Synthetic Aperture Radar (SAR) data, using Gabor's theory of wavefront reconstruction [9]. In the framework of this theory, multidimensional digital signal processing algorithms have been developed for accurate and computationally-efficient analysis of SAR data via a single or multi processor computer. This paper exhibits the utility of the SAR wavefront signal theory and its associated digital algorithms in addressing the practical information processing issues that are encountered in high-resolution and/or specialized SAR systems. We present results from two modern SAR systems. One system is the United States Navy P-3 ultra wideband UHF stripmap SAR that is intended for imaging man-made targets hidden under foliage (FOliage PENetrating, FOPEN, SAR). The other system is a high-resolution X-band spotlight SAR that is operated in an along-track monopulse, mode (single transmitter and dual receivers) for Ground Moving Target Indication (GMTI).
  • Article
    This letter conducts a point spread function (PSF) analysis for bistatic synthetic aperture radar (BSAR) systems where the transmitter is in medium Earth orbit, and the receiver is fixed on the ground. To achieve a reasonable azimuth resolution under such a configuration, the trajectory of the satellite can no longer be approximated as a straight line; therefore, current methods for PSF analysis are insufficient. The solution proposed involves extension of the generalized ambiguity function to accommodate satellite trajectory curvature. The theoretical analysis shows effects unlike those observed in monostatic or even the general BSAR and is verified by both simulation and experimental results using navigation satellites as the transmitting platforms.
  • Article
    Full-text available
    This article presents signal processing algorithms used as a new remote sensing tool, that is passive bistatic SAR with navigation satellites (e.g. GPS, GLONASS or Galileo) as transmitters of opportunity. Signal synchronisation and image formation algorithms are described for two system variants: one where the receiver is moving and one where it is fixed on the ground. The applicability and functionality of the algorithms described is demonstrated through experimental imagery that ultimately confirms the feasibility of the overall technology.
  • Article
    This letter demonstrates the feasibility of space-surface bistatic synthetic aperture radar using navigation satellites as transmitters of opportunity and a fixed ground-based receiver. Experiments with real satellite signals are described, and the obtained imagery is presented and discussed.
  • Article
    Full-text available
    This paper presents preliminary results of change detection studies using TerraSAR-X spaceborne data. Change detection is important for a variety of applications like updating maps (several years following the creation of the base map), emergency assessment following a natural catastrophe, and site monitoring. The first two cases often rely on existing geospatial information (i.e. maps) in the area of interest and involves data from different sources. Site monitoring on the other hand includes the observation of ongoing changes. Time series using an active sensor with a short revisit rate are optimal for this task. The high- resolution of TerraSAR-X and its short repeat cycle of eleven days allow reliable time series acquisitions. ACD (Amplitude Change Detection), an incoherent method, compares the backscatter of two images acquired using the same imaging parameters. It is sensitive to significant changes, i.e. changes that strongly influence the backscatter of an area. CCD (Coherence Change Detection) exploits the coherence of two SAR images acquired at different times using the same imaging parameters. They can be used to detect subtle changes occurring between the two observation dates that would remain undetected by incoherent change detection techniques. While CCD is more sensitive compared to ACD, its applicability is limited by vegetation cover. The combined use of ACD and CCD offers a more complete picture of any changes observed. KURZFASSUNG: Erste Ergebnisse zu Änderungsanalysen mit TerraSAR-X Satelliten werden vorgestellt. Änderungsanalysen sind für eine Vielzahl von Anwendungen geeignet, von der Aktualisierung von Karten über Informationsbereitstellung nach Naturkatastrophen oder zur Gebietsüberwachung. In den ersten beiden Fällen wird oftmals auf bestehende geographische Informationen (z.B. Karten) des Untersuchungsgebietes zurückgegriffen. Im Falle der Gebietsüberwachung werden Änderungen über einen bestimmten Zeitraum kartiert. Zur Erstellung dieser Zeitserien ist ein aktiver Sensor mit kurzer Wiederholrate und einer hohen räumlicher Auflösung sehr gut geeignet. TerraSAR-X hat eine Wiederholrate von elf Tagen und eignet sich damit gut zur Aufnahme von Zeitserien. Bei der nicht kohärenten ACD Methode (Amplituden Änderungsanalyse) werden die Rückstreuwerte von zwei Datensätzen, die mit denselben Parametern aufgenommen werden, verglichen. Im Falle der CCD Methode (Kohärenz Änderungsanalyse) wird die interferometrische Kohärenz zweier SAR-Datensätze, die mit denselben Parametern aufgenommen wurden, analysiert. Durch diese Technik können auch geringfügige Änderungen, die im Zeitraum zwischen den beiden Aufnahmen stattgefunden haben erkannt werden. Die Kohärenzanalyse kann zum Beispiel Aufschluss über die Nutzung von Pisten geben. Die höhere Sensitivität der CCD Methode im Vergleich zur ACD Methode wird in ihrer Anwendbarkeit durch das Vorhandensein von Vegetationsbedeckung eingeschränkt.
  • Article
    In this paper we investigate the possibility to develop a passive radar system for mid-range air target surveillance using, as illuminator of opportunity, a high EIRP level geostationary broadcast transmitter. These satellites are being introduced recently for Satellite Mobile Digital TV broadcast purpose. Since they are designed to allow mobile users to receive satellite TV without large antennas, a sufficiently high signal power is being transmitted, making them suitable as illuminators of opportunity in a passive radar system. The possibility to resort to a quasi-stationary transmitter is shown to highly simplify the signal processing required by the passive radar system. A preliminary evaluation of the achievable SNR is conducted, showing that mid-range target detection can be achieved with reliable performance. In addition, a detailed analysis of the Doppler frequency contributions is conducted. Specifically, the Doppler frequency contribution due to the motion between target and transmitter is shown to be locally independent over the target position. The overall bistatic Doppler frequency behavior is evaluated for several possible target trajectories and some critical trajectories are identified. Finally, some remarks referred to the 2D Cross Correlation Function (2D-CCF) evaluation are reported.
  • Article
    Component interfaces for sparse linear system solvers facil-itate their integration into scientific applications. Due to a great variety of sparse matrix representations and character-istics, the solver choice may be complicated. Furthermore, once chosen, the solver often needs tuning to a given appli-cation. Thus, the tasks of solver switching (on the high level of abstraction) and solver tuning may be combined calling for hierarchical linear algebra interfaces. In other words, the user may access the solver either as a whole package or as a set of tunable components. In our previous work, we proposed common interfaces for these two types of accesses. These interfaces were implemented using Common Compo-nent Architecture (CCA) specifications. In the current work, we provide and implement a hierarchical design for parallel linear system components and show the benefits of accessing sparse linear algebra functionality via integrated high-and medium-level interfaces.
  • Chapter
    This chapter introduces the basic concept of how a GPS receiver determines its position. In order to better understand the concept, GPS performance requirements are discussed first. These requirements determine the arrangement of the satellite constellation. From the satellite constellation, the user position can be solved. However, the equations required for solving the user position turn out to be nonlinear simultaneous equations, which are difficult to solve directly. In addition, some practical considerations (i.e., the inaccuracy of the user clock) are included in these equations. These equations are solved through a linearization and iteration method. The solution is in a Cartesian coordinate system and the result will be converted into a spherical coordinate system. However, the earth is not a perfect sphere; therefore, once the user position is found, the shape of the earth must be taken into consideration. The user position is then translated into the earth-based coordinate system. Finally, the selection of satellites to obtain better user position accuracy and the dilution of precision are discussed.
  • Multi-angle fusion of SS-Bi SAR images using Compass-2/Beidou-2 satellites as opportunity illuminators
    • W Tian
    • T Zhang
    • T Zeng
    Tian W, Zhang T, Zeng T, et al. Multi-angle fusion of SS-Bi SAR images using Compass-2/Beidou-2 satellites as opportunity illuminators. In: Proceedings of IEEE International Conference on Radar, Lille, 2014. 1–4
  • Chapter
    The Second Edition of this acclaimed publication enables readers to understand and apply the complex operation principles of global positioning system (GPS) receivers. Although GPS receivers are widely used in everyday life to aid in positioning and navigation, this is the only text that is devoted to complete coverage of their operation principles. The author, one of the foremost authorities in the GPS field, presents the material from a software receiver viewpoint, an approach that helps readers better understand operation and that reflects the forecasted integration of GPS receivers into such everyday devices as cellular telephones. Concentrating on civilian C/A code, the book provides the tools and information needed to understand and exploit all aspects of receiver technology as well as relevant navigation schemes: Overview of GPS basics and the constellation of satellites that comprise the GPS system Detailed examination of GPS signal structure, acquisition, and tracking Step-by-step presentation of the mathematical formulas for calculating a user's position Demonstration of the use of computer programs to run key equations Instructions for developing hardware to collect digitized data for a software GPS receiver Complete chapter demonstrating a GPS receiver following a signal flow to determine a user's position The Second Edition of this highly acclaimed text has been greatly expanded, including three new chapters: Acquisition of weak signals Tracking of weak signals GPS receiver related subjects Following the author's expert guidance and easy-to-follow style, engineers and scientists learn all that is needed to understand, build, and operate GPS receivers. The book's logical flow from basic concepts to applications makes it an excellent textbook for upper-level undergraduate and graduate students in electrical engineering, wireless communications, and computer science. © 2005 by John Wiley & Sons, Inc., Hoboken, New Jersey. All rights reserved.
  • Article
    Full-text available
    We report about the first X-band spaceborne-airborne bistatic synthetic aperture radar (SAR) experiment, conducted early November 2007, using the German satellite TerraSAR-X as transmitter and the German Aerospace Center's (DLR) new airborne radar system F-SAR as receiver. The importance of the experiment resides in both its pioneering character and its potential to serve as a test bed for the validation of nonstationary bistatic acquisitions, novel calibration and synchronization algorithms, and advanced imaging techniques. Due to the independent operation of the transmitter and receiver, an accurate synchronization procedure was needed during processing to make high-resolution imaging feasible. Precise phase-preserving bistatic focusing can only be achieved if time and phase synchronization exist. The synchronization approach, based on the evaluation of the range histories of several reference targets, was verified through a separate analysis of the range and Doppler contributions. After successful synchronization, nonstationary focusing was performed using a bistatic backprojection algorithm. During the campaign, stand-alone TerraSAR-X monostatic as well as interoperated TerraSAR-X/F-SAR bistatic data sets were recorded. As expected, the bistatic image shows a space-variant behavior in spatial resolution and in signal-to-noise ratio. Due to the selected configuration, the bistatic image outperforms its monostatic counterpart in almost the complete imaged scene. A detailed comparison between monostatic and bistatic images is given, illustrating the complementarity of both measurements in terms of backscatter and Doppler information. The results are of fundamental importance for the development of future nonsynchronized bistatic SAR systems.
  • Conference Paper
    Full-text available
    This paper presents research results in space-surface multistatic synthetic aperture radar (SS-MSAR) with non cooperative GPS satellites. The goal of this paper is to characterize such a system in an ISAR context, with a moving ground target.point spread function (PSF) are defined and used in this work to estimate the performance in term of resolution. These criteria are computed, and compared, for several scenarios with targets of different velocities.
  • Article
    This paper presents algorithms designed for a subclass of bistatic synthetic aperture radar (BSAR) called space-surface BSAR (SS-BSAR). Two SS-BSAR configurations are considered. The first one assumes a stationary, spaceborne transmitter and a moving airborne receiver. The second case is the generalized SS-BSAR configuration, where the transmitter is nonstationary. The transmitter and receiver have essentially different flight paths and velocities. For each configuration under investigation, the characteristics of the corresponding SS-BSAR received signal are examined first. Then, each proposed algorithm is derived analytically, and verified via simulation.
  • Conference Paper
    This paper concentrates on the focusing results of several hybrid bistatic SAR experiments. The hybrid bistatic configurations are referred to the case that transmitter and receiver are mounted in different kinds of platforms, e.g., spaceborne/airborne, airborne/stationary, spaceborne/stationary, and so on. Recently, we have successfully performed several hybrid bistatic SAR experiments, i.e. TerraSAR/PAMIR, PAMIR/stationary, and TerraSAR/ stationary. In this paper, we will emphasize the imaging geometry, image analysis, and the frequency-domain focusing results.
  • Conference Paper
    This paper describes the first experiment in bistatic high resolution SAR using a stationary receiver and TerraSAR-X as transmitter. Implicitly it also describes the first important component of a SAR sensor developed at the Center for Sensorsystems. After evaluating the bistatic geometry, an overview of the hardware setup and a short performance analysis is given. First processed results are presented from data, taken in a number of experiments performed in 2009.
  • Article
    The spatial separation of the transmitter and the receiver in bistatic synthetic aperture radar (SAR) enables a variety of data acquisition geometries to achieve benefits like the increased information content of bistatic SAR data. In the case of hybrid bistatic SAR constellations where the transmitter is spaceborne and the receiver is onboard an aircraft, one has to deal with a huge discrepancy between platform velocities. This paper presents bistatic spaceborne/airborne SAR experiments, where the radar satellite TerraSAR-X is used as a transmitter and the airborne SAR sensor Phased Array Multifunctional Imaging Radar (PAMIR) of the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) is used as a receiver. Both sensors are equipped with phased-array antennas, which offer the possibility of beam steering and could be used for the first time for the “double sliding spotlight mode.” In this mode, the space- and airborne sensors operate with different sliding factors (ratio between footprint and platform velocity). The performance of two different experiments is analyzed, and the novel double sliding spotlight mode is presented. This paper describes the experimental setups, the synchronization system, and the data acquisition. The image results were processed by a modified backprojection algorithm and a frequency-domain algorithm. The analysis of the final bistatic images comprises the spatial resolution and the scattering behavior of selected objects. Parts of the bistatic SAR images are compared with the corresponding monostatic images of PAMIR and TerraSAR-X. It will be shown that hybrid bistatic SAR is a worthwhile and helpful addition to current monostatic SAR.
  • Article
    This study presents the synchronisation problem in `space-surface bistatic synthetic aperture radar (SS-BSAR)` system. Global Navigation Satellite Systems (GNSS) are considered as transmitters of opportunity. It highlights various important issues of synchronisation, specifically related to SS-BSAR utilising GLONASS as the transmitter. Experimental testing of the synchronisation algorithm is described and verified using the GLONASS satellite. Also, experimental images obtained from GLONASS are presented and briefly analysed.
  • Conference Paper
    Space-Surface BSAR (SS-BSAR) is a kind of special BSAR configuration deeply researched in recent years. In this paper, based on the SS-BSAR configuration, a modified RMA is presented. The algorithm considers the three-dimensional geometry structure and obtains the accurate two-dimensional spectrum function of point target. However because of the space-variant property of spectrum function, the phase compensation of high accuracy is carried out, furthermore, the simulation results fully demonstrates the correctness and efficiency of the algorithm proposed.
  • Conference Paper
    Future bi- and multistatic SAR systems could support the scientific community and the commercial market with an additional and powerful tool for imaging and exploration of interesting areas on earth. With the diversity of geometries between transmitter and receivers one can achieve for instance improvements in scene classification, extractions of particular features, and cost reduction. New experiments are necessary to investigate the advantages as well as the problems of bi- and multistatic SAR systems. This paper describes the bistatic use of the spaceborne SAR system TerraSAR-X for future space- borne/airborne SAR exploration. TerraSAR-X will illuminate a particular scene while the receiver, the airborne SAR system PAMIR, will collect the reflected signals on board of an aircraft.
  • Article
    The signal processing of the medium-Earth-orbit synthetic aperture radar (SAR) is more challenging than that of the current low-Earth-orbit SAR because the imaging geometry is more complicated, and the range and azimuth variances are more severe. This paper deals with these imaging problems in three aspects. First, an advanced hyperbolic range equation (AHRE) is proposed for the first time, which is more precise for a spaceborne SAR than the conventional hyperbolic range equation (CHRE). Second, the point target spectrum based on the AHRE is analytically derived, which is useful for developing efficient SAR processing algorithms. Third, the well-known nonlinear chirp scaling (NLCS) algorithm is modified according to this new spectrum, and the so-called AHRE-based advanced NLCS (A-NLCS) algorithm is established. The simulation results validate the correctness of our method for L-band SAR systems at altitudes from 1000 to 10000 km with an azimuth resolution around 3 m. It is also shown that the A-NLCS algorithm has better performance than the CHRE-based algorithms in longer integration time cases. Therefore, we recommend the A-NLCS algorithm for a spaceborne SAR with a lower frequency, finer resolution, and higher satellite altitude.
  • Article
    The spatial separation of the transmitter and the receiver in bistatic synthetic aperture radar (SAR) enables a variety of data acquisition geometries to achieve benefits like the increased information content of bistatic SAR data. In the case of hybrid bistatic SAR constellations where the transmitter is spaceborne and the receiver is onboard an aircraft, one has to deal with a huge discrepancy between platform velocities. This paper presents bistatic spaceborne/airborne SAR experiments, where the radar satellite TerraSAR-X is used as a transmitter and the airborne SAR sensor Phased Array Multifunctional Imaging Radar (PAMIR) of the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) is used as a receiver. Both sensors are equipped with phased-array antennas, which offer the possibility of beam steering and could be used for the first time for the “double sliding spotlight mode.” In this mode, the space- and airborne sensors operate with different sliding factors (ratio between footprint and platform velocity). The performance of two different experiments is analyzed, and the novel double sliding spotlight mode is presented. This paper describes the experimental setups, the synchronization system, and the data acquisition. The image results were processed by a modified backprojection algorithm and a frequency-domain algorithm. The analysis of the final bistatic images comprises the spatial resolution and the scattering behavior of selected objects. Parts of the bistatic SAR images are compared with the corresponding monostatic images of PAMIR and TerraSAR-X. It will be shown that hybrid bistatic SAR is a worthwhile and helpful addition to current monostatic SAR.
  • Conference Paper
    In this paper, a multistatic radar system with multiple receivers and one transmitter is analyzed. We address the rules for selecting the weights for fusing multiple receivers in order to meet pre-specified performance goals. A multistatic radar ambiguity function is used to relate different radar performance measures to system parameters such as radar geometry and radar waveforms. Simulations are used to demonstrate that different performance criteria can lead to different rules for combining the signals from multiple receivers.
  • Conference Paper
    This paper presents research results in space-surface bistatic synthetic aperture radar (SS-BSAR) with GNSS non-cooperative transmitters. The experimental-setup used to study the SS-BSAR is described. The signal processing algorithm that will be used to process the data collected from SS-BSAR is also discussed
  • Conference Paper
    The concept and preliminary analysis of the Interferometric SS-BSAR system is discussed in this paper.
  • Conference Paper
    The ambiguity function (AF) for bistatic synthetic aperture radar (BSAR) is deduced and the performance of space-surface bistatic SAR (SS-BSAR) is analyzed. SS-BSAR can operate utilizing non-cooperative transmitters such as GPS, GALILEO, etc due to its bistatic nature.
  • Conference Paper
    Full-text available
    The paper introduced a feasibility analysis of a synthetic aperture radar (SAR) with novel architecture. Two essential peculiarities are discussed: the system configuration with a moving transmitter when the receiver is stationary and noncooperative transmitters utilization for the system. The system is named space-surface BSAR or S-SBSAR. The system analysis confirms its feasibility. S-S SAR could find numerous applications where an observation area of ∼20-30 km relevant to the receiver is acceptable. S-SBSAR space resolution corresponds to the general approach to BSAR when the resolution degradation due to a non-optimal satellite-targets-receiver geometrical position could be resolved using the satellites diversity.
  • Conference Paper
    Bistatic radar has long been recognised as an interesting variant of radar, with a number of potential advantages for air defence. Space-based radar is seen by the US Department of Defense as a key technique for future AMTI and GMTI applications, and the DISCOVERER II programme is indicative of current thinking, aiming ultimately at a network of several tens of satellites. This system would also involve bistatic receivers to give near-continuous surveillance. The purpose of this paper is to present a system concept for a bistatic radar using a satellite-based illuminator of opportunity and a static ground-based receiver. The paper presents system design and performance calculations, and describes experiments to be performed.
  • Article
    Power budget analysis is considered for signal detection in bistatic synthetic aperture radar, with global navigation satellite systems acting as non-cooperative transmitters. The signal detection is analysed against thermal noise, in addition to interference introduced by the transmitting satellites sharing the same frequency bands. Two basic radar receiver configurations are considered: on an aeroplane; stationary on the ground.
  • Article
    Passive radars using illuminators of opportunity have attracted much attention in the international radar community. One existing radio transmission system that may be utilised for this purpose is the Global System for Mobile communication (GSM). This paper presents a study showing the feasibility of using a GSM signal for passive radar. The analysis of the GSM waveform, and any significance or influence it has with respect to the passive radar design considerations are investigated in detail. The paper describes fully the design and implementation of a low-cost GSM-based passive radar prototype in addition to the associated signal processing scheme. Numerous measurements for various ground-moving targets were investigated extensively. The preliminary processing results demonstrate the feasibility of using GSM signals as a radar waveform and have the potential capability to detect and track different types of ground-moving targets.
  • Article
    The paper discusses the bistatic radar parameters for the case when the transmitter is a satellite emitting communication signals. The model utilises signals from an Iridium-like low Earth orbiting satellite system. The maximum detection range, when thermal noise-limited, is discussed at the theoretical level and these results are compared with experimentation. Satellite-radar signal levels and the power of ground reflections are evaluated
  • Article
    Full-text available
    In repeat-pass interferometric synthetic aperture radar (SAR), man-made scene disturbances are commonly detected by identifying changes in the mean backscatter power of the scene or by identifying regions of low coherence. Change statistics such as the sample mean backscatter-power ratio and the sample coherence, however, are susceptible to high false-alarm rates unless the change in the mean backscatter power is large or there is sufficient contrast in scene coherence between the changed and unchanged regions of the image pair. Furthermore, as the sample mean backscatter-power ratio and sample coherence measure different properties of a SAR image pair, both change statistics need to be considered to properly characterize scene changes. In this paper, models describing the changed and unchanged regions of a scene are postulated, and the detection problem is expressed in a Bayesian hypothesis-testing framework. Forming the log-likelihood ratio gives a single sufficient statistic, encoding changes in both the coherence and the mean backscatter power, for discriminating between the unchanged- and changed-scene models. The theoretical detection performance of the change statistic is derived and shows a significant improvement over both the sample mean backscatter-power ratio and sample coherence change statistics. Finally, the superior detection performance of the log-likelihood change statistic is demonstrated using experimental data collected using the Defence Science and Technology Organisation's Ingara X-band airborne SAR
  • Article
    Full-text available
    Several techniques for detecting temporal changes in satellite synthetic-aperture radar (SAR) imagery are compared, using both theoretical predictions and spaceborne SAR data collected by the first European Remote Sensing Satellite, ERS-1. In a first set of techniques, changes are detected based on differences in the magnitude of the signal intensity between two dates. Ratioing of the multidate radar intensities is shown to be better adapted to the statistical characteristics of SAR data than subtracting, and works best when the number of looks is large. In a second set of techniques, changes are detected based on estimates of the temporal decorrelation of speckle. This method works best with one-look complex amplitude data, but can also be used with intensity data provided that the number of looks is small. The two techniques are compared using actual SAR data collected by ERS-1. The results illustrate the viability as well as the complementary character of these techniques for detecting changes in the structural and dielectric properties of remotely sensed surfaces
  • Article
    Full-text available
    Bistatic synthetic aperture radars (BSARs) have been the focus of increasing research activity over the last decade. The generalized ambiguity function (GAF) of bistatic SAR is introduced here. First, the GAF for BSAR is represented in the delay-Doppler domain, and is then expanded to the spatial (coordinates) domain. From the GAF, comprehensive knowledge regarding the resolution of BSAR can be extracted, including the range and azimuth resolutions, as well as the area of a resolution cell of BSAR. These general results are also applied to the performance analysis of several particular BSAR geometries, including the space-surface-BSAR (SS-BSAR) system, to demonstrate the potential ability of this newly introduced system.