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ABSTRACT: This paper presents a new bistatic point target reference spectrum. It is derived by using the 2-D principle of stationary phase which is first applied in the synthetic aperture radar (SAR) community. The spectrum contains two hyperbolic range-azimuth coupling terms and thus is very similar to the monostatic spectrum. It shows the characteristic of the conventional monostatic SAR besides an additional azimuth scaling term. Therefore, it makes the common Doppler-based monostatic processing algorithms readily suitable to handle the Bistatic SAR (BiSAR) data in the moderate-squint azimuth-variant configurations with two moving platforms. Based on the spectrum, two Doppler-based monostatic imaging algorithms [i.e., range-Doppler algorithm (RDA) and chirp-scaling algorithm (CSA)] are readily implemented to deal with the moderate-squint azimuth-variant BiSAR data. Compared to the processing procedure for the monostatic SAR, the RDA and CSA for the BiSAR need only the adjustment of Doppler parameters. Finally, the potential and limitation of the spectrum are analyzed, and the real raw data in the spaceborne/airborne configurations are used to validate the proposed spectrum and processing methods.
IEEE Transactions on Geoscience and Remote Sensing 11/2011; · 2.89 Impact Factor
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ABSTRACT: Forward-looking radar imaging continues to gain in significance due to a variety of convenient applications, like landing assistance for aircraft in poor visibility conditions. Synthetic aperture radar (SAR) techniques are typically used to achieve a high azimuth resolution, but conventional monostatic SAR is not applicable in forward direction because of azimuth ambiguities and poor Doppler resolution. To improve the Doppler resolution and to avoid azimuth ambiguities, bistatic SAR configurations can be used to obtain high-resolution radar images. This is demonstrated for the first time in a spaceborne-airborne SAR experiment by using TerraSAR-X as the illuminator and the Phased Array Multifunctional Imaging Radar as the receiver. For convenience, the receiver's SAR antenna was mounted on the aircraft's loading ramp and looked backward. Due to identical image properties and the same challenges for forward- and backward-looking sensors, this configuration also demonstrates the feasibility of forward-looking bistatic SAR. This letter describes the experimental setup, analyzes the performance, and presents the imaging results.
IEEE Geoscience and Remote Sensing Letters 08/2011; · 1.56 Impact Factor
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ABSTRACT: 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.
IEEE Transactions on Geoscience and Remote Sensing 09/2010; · 2.89 Impact Factor
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ABSTRACT: Bistatic synthetic aperture radar (SAR) operates with spatially separated transmit and receive antennas that are mounted on separated platforms. Provided that there is an overlap of both antenna footprints, the platforms can move with different velocities in arbitrary directions. A special configuration is given, when the receive antenna looks in forward direction, which is called bistatic forward-looking SAR. Besides the well known advantages of bistatic SAR like the increased information content of the data because of different RCS and scattering characteristics, such a configuration enables high resolution imaging in forward direction, which is not possible with conventional monostatic SAR systems. This paper analyzes a bistatic forward-looking configuration and demonstrates the capability and feasibility of imaging in forward or backward direction using the radar satellite TerraSAR-X as transmitter and the airborne SAR system PAMIR as receiver.
Geoscience and Remote Sensing Symposium (IGARSS), 2010 IEEE International; 08/2010
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ABSTRACT: This paper presents a frequency-domain-based focusing algorithm for the bistatic synthetic aperture radar (BiSAR) data in airborne/stationary configuration. In this bistatic configuration, only the moving platform contributes to the azimuth modulation, whereas the stationary platform introduces a range offset (RO) to the range migration trajectories of targets at the same range. The offset is determined by the azimuth position of different targets with respect to the stationary platform. Since the RO is position dependent, monostatic SAR imaging algorithms are not able to focus the bistatic data collected in this configuration. In this paper, an analytical bistatic point-target reference spectrum is derived, and then, a frequency-domain-based algorithm is developed to focus the bistatic data. It uses an interpolation-free wavenumber-domain algorithm as a basis and performs a range-variant interpolation to correct the position-dependent RO in the image domain after coarse focusing. The proposed algorithm is validated by the simulated data and the real BiSAR data acquired by the Forschungsgesellschaft fu??r Angewandte Naturwissenschaften's airborne SAR system, PAMIR, in December 2007. In this BiSAR experiment, an X-band transmitter was stationary operated on a hill with PAMIR as the receiver mounted on a Transall C-160.
IEEE Transactions on Geoscience and Remote Sensing 02/2010; · 2.89 Impact Factor
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ABSTRACT: Bistatic SAR is a promising and useful supplement to a classical monostatic SAR system. Since transmitter and receiver are spatially separated, additional information of a scene may be provided. Further, as shadowing, layover, and foreshortening depend on the bistatic geometry, which can be quite different to the monostatic case, they can contribute to image analysis and classification. The transmitter and receiver are located on different platforms, which may either be close together or hundreds of kilometers apart. Typical platforms are satellites, UAVs, aircrafts, and towers. This paper presents recent bistatic SAR experiments with spaceborne, airborne, and stationary sensors, which have been conducted at FHR or in cooperation with Defence Research & Development Canada. Image results are presented and analyzed with respect to scattering behavior and resolution and compared to monostatic images.
Geoscience and Remote Sensing Symposium,2009 IEEE International,IGARSS 2009; 08/2009
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ABSTRACT: The multi-input / multi-output (MIMO) principle is well known for communication applications, whereas at least the name dasiaMIMOpsila is relatively new for radar applications. Nevertheless, the principle has been analyzed and used in a few examples since the early 80s or even before. A MIMO-radar is characterised by a number N of transmitting and a number M of receiving antennas forming N times M Tx/Rx pairs where each propagation path from the nth transmit antenna to the object to the mth receive antenna is made available to the signal processing. This can be achieved by temporal multiplexing, spatial coding and/or orthogonal waveforms. A further step is to transfer this technique to the SAR case. Additionally, the whole array is moving, SAR processing can be applied. Possible geometries of MIMO-SAR are along track arrays (reduction of azimuth-ambiguities, moving target indication, super resolution) or across track arrays (reduction of elevation-ambiguities, interferometry, 3D down-looking SAR). In this paper, some aspects of moving MIMO-arrays for SAR will be addressed.
Radar Conference, 2009 IEEE; 06/2009
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ABSTRACT: This paper presents a wide area traffic monitoring experiment under real conditions, using the scan-MTI mode of the airborne radar sensor PAMIR. This flexible GMTI (Ground Moving Target Indication) mode was designed in order to rapidly monitor wide areas for moving targets. The scan operation enables the detection of targets from different aspect angles with a high revisit rate. The parameters (e.g., radial velocity, signal-to-noise ratio, and positioning accuracy) of the detected vehicles are investigated and compared to the expected theoretical GMTI performance. It will be shown that the scan-MTI mode is particularly adapted to perform an efficient wide-area traffic monitoring.
IEEE Transactions on Geoscience and Remote Sensing 11/2008; · 2.89 Impact Factor
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ABSTRACT: ARTINO<sup>1</sup> is a new radar system, integrated in a small mobile and dismountable experimental UAV<sup>2</sup>. The side- looking geometry of usual SAR<sup>3</sup> systems produces shading effects of the scene to be imaged. ARTINO overcomes this restriction with the ability to image the direct overflown area (Nadir looking) in three dimensions. The effects caused by vibrations of the used sparse MIMO<sup>4</sup> antenna array- which is embedded in the wings of the airplane - are discussed with respect to the 3D imaging quality. A correction approach within the image formation process is presented, too.
Geoscience and Remote Sensing Symposium, 2007. IGARSS 2007. IEEE International; 08/2007
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ABSTRACT: This paper presents some Scan-MTI results, which were obtained with the SAR-GMTI system PAMIR developed at FGAN-FHR. The Scan-MTI mode was designed to rapidly monitor wide areas for ground moving targets. The scan operation enables detection of targets from different aspect angles with a high revisit rate. This mode is particularly adapted to perform an efficient traffic monitoring, as well.
Geoscience and Remote Sensing Symposium, 2007. IGARSS 2007. IEEE International; 08/2007
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ABSTRACT: The separation of transmitter and receiver makes bistatic SAR (synthetic aperture radar) systems preferable to conventional monostatic systems in several applications. However, this separation also leads to difficulties in image processing and in synchronization of the involved systems. For the upcoming hybrid bistatic SAR experiment with the TerraSAR-X satellite as transmitter and the airborne SAR/GMTI system PAMIR as receiver the synchronization issues are discussed in this paper and possible solutions are presented.
Geoscience and Remote Sensing Symposium, 2007. IGARSS 2007. IEEE International; 08/2007
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ABSTRACT: The development of new technologies and algorithms in the field of bistatic SAR will lead to new instruments of remote sensing in various domains. One of the next important steps will be the realisation of challenging bistatic SAR experiments to prove, evaluate, and develop this new technique. In this context, we will conduct hybrid bistatic SAR experiments using the SAR satellite TerraSAR-X and the airborne SAR sensor PAMIR. This paper presents first considerations with respect to the optimisation of possible geometries between the spaceborne and the airborne SAR sensor.
Geoscience and Remote Sensing Symposium, 2006. IGARSS 2006. IEEE International Conference on; 09/2006
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ABSTRACT: The new radar system ARTINO (Airborne Radar for Three-dimensional Imaging and Nadir Observation) allows to image a direct overflown scene in three dimensions. Integrated in a small, mobile, and dismountable UAV (Unmanned Aerial Vehicle) it will be an ideal tool for various applications. This paper presents the image formation and first processing results of simulated raw data.
Fraunhofer FHR.
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ABSTRACT: The new radar system ARTINO (Airborne Radar for Three-dimensional Imaging and Nadir Observation), developed at FGAN-FHR, allows to image a direct overflown scene in three dimensions. Integrated in a small, mobile, and dismountable UAV (Unmanned Aerial Vehicle) it will be an ideal tool for various applications. This paper gives an overview about the ARTINO principle, the raw data simulation, the image formation, the technical realisation, and the status of the experimental system.
Fraunhofer FHR.
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ABSTRACT: The development of new technologies and algorithms in the field of bistatic SAR will lead to new instruments of remote sensing in various domains. One of the next important steps will be the realisation of challenging bistatic SAR experiments to prove, evaluate, and develop this new technique. In this context, we will conduct hybrid bistatic SAR experiments using the SAR satellite TerraSAR-X and the airborne SAR sensor PAMIR. This paper presents first considerations with respect to the optimisation of possible geometries between the spaceborne and the airborne SAR sensor.
Fraunhofer FHR.
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ABSTRACT: 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.
Fraunhofer FHR.
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J.H.G. Ender, J. Klare,
I. Walterscheid,
A.R. Brenner,
M. Weiß,
C. Kirchner,
H. Wilden,
O. Loffeld,
A. Kolb,
W Wiechert,
M. Kalkuhl,
S. Knedlik,
U. Gebhardt,
H. Nies,
K. Natroshvili,
S. Ige,
A. Ortiz,
A. Amankwah
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ABSTRACT: Following the goals of our cooperation treaty between FGAN and ZESS (University Siegen), we work closely together on the complex research field of bistatic exploration. Single tasks of the overall topic are for instance experimental missions, processing, image formation, position- and attitude estimation, synchronisation, simulation, parameter estimation, and visualization. This paper presents an overview about the common projects of FGAN, ZESS, and FOMAAS.
Fraunhofer FHR.
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ABSTRACT: 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 promising experiments are necessary to investigate advantages and disadvantages of bi- and multistatic SAR system. This paper presents some challenging problems and possible solutions of future hybrid SAR exploration using a spaceborne transmitter and an airborne receiver. Special aspects like the resolution of the point spread function derived from the k-space or the estimation of the SNR will be shown. Finally, new intended bistatic spaceborne/airborne SAR experiments between TerraSAR-X and PAMIR will be discussed.
Fraunhofer FHR.
