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Research Of Interferometric 3D ISAR Imaging For Space Target

Posted on:2016-08-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:L Z ZhaoFull Text:PDF
GTID:1108330476950664Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
Space objects include many kinds of orbiting objects, such as artificial satellites, space stations, spacecrafts and debris, etc. With the development of the space technology, human’s space activities become more frequently. This results in the dramatically increasing population of space objects and a more complex space environment. Therefore, surveillence, tracking and recognition of the space objects is becoming more and more important. Interferometric inverse synthetic aperture radar(InISAR) imaging is a promising technique and has received much attention, which can provide the three dimensional images for target recognition. InISAR three dimensional imaging approaches can be categorized into two types according to the difference of echo sources, one is based on the echo from different arcs of the space objects and the other is based on the echo from different receiving antennas. According to the type of motion compensation methods, they also can be categorized into two types, one based on motion model analysis and the other based on autofocusing algorithms. This dissertation mainly focuses on interferometric three dimensional ISAR imaging of the space objects, and makes an intensive study on the relative motion analysis between space target and the radar, phase compensation, image registration and the interferometric three dimensional ISAR imaging based on double-arc echoes.First, according to the basic principle of InISAR three dimensional imaging, the mathematical expression for the interferometric phase is derived in the case of both normal mode and squint mode, which consists of scatterers’ coordinates, the length of baseline and other inteferometric parameters. After that, the relative motion between an earth based radar and a space object is investigated. With respect to the object coordinates, the analysis of the radar line of sight(LOS), the tangential velocity vector and the relative rotation angular velocity vector are accomplished with elementary vector algebra. Subsequently the cartesian coordinate system corresponding to each ISAR image is obtained. By analyzing the changes of LOS at the azimuth and elevation direction respectively, and by comparing ISAR images under different accumulating angles and arcs, the relationships between the variable relative rotation of space objects and the ISAR images are obtained, which would provide a support for the future research such as ISAR imaging, InISAR 3-D imaging and so on.Second, several crucial issues about the InISAR 3-D imaging technology are researched, for example, image registration, translational motion compensation and phase compensation for ISAR imaging. At the beginning, the mismatch of two ISAR images is analyzed under different target motion directions, and the constraint to the interferometric angle is derived. For the translational motion compensation, the effects of different motion compensation approaches such as parametric and non-parametric methods on the interferometric imaging are analyzed. Following that, a method is proposed to remove the additional linear phase that is induced during the image interpolation process. Finally, the image defocusing and phase error problems caused by the non-uniform rotation of image plane are analyzed, a method based on the fractional Fourier transform is proposed to solve these problems.Third, interferometric ISAR imaging is investigated by exploiting double arc segment echoes. According to the space target motion model, the double-arc interferometric scenario is established, and several parameters to be used are defined, such as the imaging plane dihedral angle, image rotation angle, vertical and parallel interferometric angles. By building the echo model, the analytical expression of scatterer’s height is deduced with the interferometric phase and the predefined angle parameters. The difference between two ISAR images generated from two different arc echo are analyzed, and an approach is proposed to solve the image scale mismatch problem and to prepare ISAR images for image registration. Constraints to the dihedral angle are obtained to meet the requirements of image registration and estimation accuracy of height. On the basis of these constraints, the interferometric arc segment selection methods are proposed both in the single-pass and multi-pass cases. Simulation results have verified the effectiveness of the proposed method.
Keywords/Search Tags:Interferometric Inverse Synthetic Aperture Radar(InISAR), space objects ISAR imaging, three dimensional ISAR reconstruction, image registration, space objects motion model, double arc segment interferometric imaging
PDF Full Text Request
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