# Estimating the Observation Area of a Stripmap SAR via an ISAR Image Sequence  
[PERSON]  
1 The School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China;  
1 [EMAIL_ADDRESS] (H.C.); [EMAIL_ADDRESS] (J.W. ); [EMAIL_ADDRESS] (T.F. ); [EMAIL_ADDRESS] (S.Z)  
[PERSON]  
1 The School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China;  
1 [EMAIL_ADDRESS] (H.C.); [EMAIL_ADDRESS] (J.W. ); [EMAIL_ADDRESS] (T.F. ); [EMAIL_ADDRESS] (S.Z)  
[PERSON]  
1 The School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China;  
1 [EMAIL_ADDRESS] (H.C.); [EMAIL_ADDRESS] (J.W. ); [EMAIL_ADDRESS] (T.F. ); [EMAIL_ADDRESS] (S.Z)  
[PERSON]  
1 The School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China;  
1 [EMAIL_ADDRESS] (H.C.); [EMAIL_ADDRESS] (J.W. ); [EMAIL_ADDRESS] (T.F. ); [EMAIL_ADDRESS] (S.Z)  
[PERSON]  
263610 Uint, Korla 841001, China; [EMAIL_ADDRESS] 263610 Uint, Korla 841001, China; [EMAIL_ADDRESS] 263610 Uint, Korla 841001, China; [EMAIL_ADDRESS] 63610 Uint, Korla 841001, China; lihaguang2012@126.  
space targets [3]. Therefore, ISARs can be used to obtain image sequences of spaceborne SARs to estimate the area observed by spaceborne SARs operating in stripmap mode. Since the area observed by the spaceborne SAR operating in stripmap mode is time-varying, in practice, it is difficult to establish a mathematical model to directly estimate it. Considering the characteristics of spaceborne SARs operating in stripmap mode, the time-varying observation area can be parameterized into the fixed attitude of the spaceborne SAR antenna. Therefore, the corresponding relation between the area observed by the spaceborne SAR operating in the stripmap mode and the fixed attitude of the spaceborne SAR's antenna can be established. Then, by estimating the fixed attitude of the spaceborne SAR's antenna, the area observed by the spaceborne SAR in the stripmap mode can be estimated. Reviewing the relevant literature on the attitude estimation of space targets based on ISAR imaging technologies, the existing research methods can be generally sorted into the three following categories: (1) Three-dimensional structure reconstruction methods. A ground-based radar performs ISAR imaging for space targets from multiple perspectives; then, the relation between the observation geometry and the 3D structure of the space target is established, and the expression of the 3D structure of the space target is derived, thereby estimating the attitude of the space target. Drawing inspiration from the Structure From Motion (SFM) methods in the computer vision field [4; 5], the radar observation matrix of space target scatterers can be decomposed using the Singular Value Decomposition (SVD) algorithm. Then, the structure matrix and measurement matrix are obtained to estimate the shape and position information of the space target in 3D space [6; 7; 8]. Interferometric Synthetic Aperture Radar (InSAR) imaging technology can be used to acquire instantaneous 3D point cloud models of space targets [9; 10]. Subsequently, the space target's attitude can be extracted by analyzing the 3D point cloud. However, the angular scattering phenomenon, which exists when scatterers on the space target are observed from multiple perspectives, affects the performance of the SVD algorithm. In addition, the phase ambiguity and interferometric baseline configuration issues are great challenges for interferometric ISAR imaging. The above problems cause the reconstructed 3D structure of the space target to be less stable, thereby affecting the accuracy of the space target attitude estimation. (2) Space target special structural feature extraction methods. In recent years, many scholars have proposed a large number of space target attitude estimation methods based on the special structural features of the space target body or components.