Study On Monostatic ISAR 3-D Imaging Technique Of Space Object

Three-dimensional imaging of the Inverse Synthetic Aperture Radar has important application perspective in the fields of tracing and identifying external space targets, such as satellites and space fragments, and observing celestial body. At the present time,the conventional method to make 3-D imaging of motion targets is Inverse Synthetic Aperture Radar Interferometry. The 3-D image made by InISAR is composed of altitude and azimuth-range information of radar-target. Scattering centers on target which are at the same azimuth and range but different altitudes can't be distinguished in this image. So it isn't a real 3-D image of target. This method also has some difficulty and complexity in imaging algorithm. Taking into account problems of the above method and characteristics that motion parameters of space objects can be measured, an inverse synthetic aperture 3-D imaging technique is studied which makes 3-D image of target using monostatic radar. This technique includes three kinds of 3-D imaging methods, namely range-doppler method, a 3-D imaging method based on one dimensional range profile of ISAR target and a 3-D imaging method based on 2-D echoed data of ISAR target.For the first method, the turntable imaging theory of ISAR and 3-D expression of echo signal are studied. A method is proposed which makes 3-D image of space objects by using R-D imaging algorithm. The original ISAR echo data of a target model is simulated and coherently processed to generate a 3-D image of the target model by using R-D imaging method. The experimental results show that 3-D image of three-dimensional rotation space objects can be generated by R-D algorithm. But the method requires that target must have 3-D rotation motion relative to radar and resolutions of 3-D image are limited by rotation angle.For the secend method, based on the geometric projection of scattering centers on the line of radar sight, a method for reconstructing the 3-D distribution of target is performed, using multiple 1-D range profiles in different times. After analyzing principle of 3-D radar imaging, the methods for estimating range and mechanism for scattering centers match and extrction, space spectrum estimation algorithms for estimating range is presented, and an match and extraction imaging method is proposed based on statistics histogram and c-means algorithm.The imaging experiments based on simulation data are developed, and experimental result indicates that this 3-D imaging method is not restricted by motion way of targets and shows the validity and robustness of the preformed method.For the third method, ISAR 2-D echoed data and 2-D all-pole modeling are studied. After analyzing 3-D imaging theory using 2-D echoed data in different times and the methods for estimating parameters, a method for reconstructing the 3-D distribution of target and an 2-D spectral estimation algorithm(ACMP) for estimating parameters are performed. .The imaging experiments based on simulation data are developed, and experimental result also indicates that this 3-D imaging method is not restricted by motion way of targets and shows the validity and robustness of the preformed method.