# High-Resolution and Wide-Swath 3D Imaging for Urban Areas Based on Distributed Spaceborne SAR
)1 National Key Laboratory of Microwave Imaging Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; [EMAIL_ADDRESS] (Y.Y. ); [EMAIL_ADDRESS] (R.W. ); [EMAIL_ADDRESS] (Y.W. )1 National Key Laboratory of Microwave Imaging Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; [EMAIL_ADDRESS] (Y.Y. ); [EMAIL_ADDRESS] (R.W. )1 National Key Laboratory of Microwave Imaging Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; [EMAIL_ADDRESS] (Y.Y. );research on the E-SAR system platform. In 2005, [PERSON] et al. [8] used the mapping data of the Naples area obtained by the European Remote Sensing Satellite heavy orbit flight to realize 3D imaging of spaceborne tomographic SAR for the first time. In 2010, a team led by [PERSON] from DLR [9] used TerraSAR-X data to obtain 3D imaging results of complex urban scenes for the first time. Later, the team carried out much spaceborne TomoSAR research using satellite data [10; 11; 12], which has made a significant contribution to the development of TomoSAR 3D imaging. In 2013, the ESA Program Board decided to implement Biomass as the 7 th Earth Explorer Mission within the frame of the ESA Earth Observation Envelope Programme [13], which is the first SAR spaceborne mission specifically designed to conduct tomography from space, with a repeat-pass configuration. With the rapid development of deep learning, more research is combining it with 3D imaging to achieve efficient imaging [14; 15]. The authors of [14] constructed the CTV-driven optimization model to pursue precise estimations in weakly sparse scenarios. The authors of [15] proposed a network called kR-Net to achieve high-resolution imaging of intricate targets, which was previously impossible. However, the above multi-baseline data are obtained with a repeat-pass configuration, resulting in strong temporal decorrelation, which makes the tomographic focusing of targets more difficult. Although the TomoSAR technology has gradually developed and improved with the assistance of abundant data resources, there are several problems with traditional 3D imaging. First, traditional 3D imaging takes a long time in a wide mapping area, causing low efficiency and high costs. Meanwhile, the traditional 3D imaging system has a short baseline length and few channels, which results in serious data redundancy. Therefore, it is necessary to develop an HRMS platform to achieve wide application prospects of SAR tomography technology. Distributed SAR can realize 3D imaging of targets in a single flight. The distributed SAR satellite system [16] is composed of multiple satellites flying in a formation that can break through the size limitation of traditional large satellites and provide various baseline combinations and globally stable baselines. It conducts cooperative work through communication, formation control, and joint signal processing to complete the earth observation task, improve the performance of the system in HRMS imaging and 3D imaging, reduce the system cost, and shorten the development cycle, so it has important strategically important significance and research value. Significant international research work in distributed spaceborne SAR systems includes the TechSAT-21 mission [17; 18; 19] RadarSat-2/3 [20; 21], Cartwheel plan [22], Cosmo skymed plan [23], TerraSAR-X and TanDEM dual satellite formation plan [24; 25], and SAR-Lupe five satellite formation networking plan. TerraSAR-X and TanDEM form a dual satellite, which is the only distributed spaceborne SAR system operating in orbit and has completed a high-precision global 3D topographic survey. However, the system can only realize interferometry in a single flight. The multi-channel distributed SAR system scheme proposed in this paper can realize 3D imaging in a single pass.