# Estimating the Observation Area of a Stripmap SAR via an ISAR Image Sequence
## 5 Experimental Results and Analysis  
In this section, the results of the feasibility verification experiment are shown and analyzed. Then, the results of the robustness validation experiment are shown and analyzed. Feasibility Results and Analysis of the Algorithm for Minimizing the Dihedral Angle between the Estimated Plane and Actual Plane  
Figure 13 shows the geometrical relation between the plane containing the scatterers estimated using (27) on the parabolic antenna edge, under the condition of a non-ideal look angle, and the plane containing the actual parabolic antenna edge of spaceborne SAR. There is a very obvious dihedral angle between the two planes. Therefore, it is feasible to construct the objective function in (30). Although the spaceborne SAR model in this article is based on the assumption that the spaceborne SAR has a parabolic antenna, it is still applicable for electronically scanned phased array panel antennas because the proposed method is based on the coplanarity of the scatterers of the spaceborne SAR antenna, which is not limited to a paraboloidal shape or a rectangular shape. Figures 14 and 15 show the estimation error distributions of the antenna look angle when the spaceborne SAR is operating in boresight stripmap mode using low-elevation arc segments and high-elevation arc segments. It is obvious that, for all the estimated arc segments, the estimation errors of the look angle are within the quantization unit of the search scope, and the proposed method has high accuracy and good performance. Therefore, the feasibility of the method proposed in this article is validated. Although, in this experiment, based on the advantages of a spaceborne SAR operating in boresight stripmap mode and the common practice in the industry, the model is performed under the assumption that the spaceborne SAR operates in boresight stripmap mode, the method proposed in this article is still applicable for scenarios in which the spaceborne SAR operates in squinted mode. In the squinted case, it is only necessary to assume that the antenna component performs yaw and roll rotation relative to the satellite body, and then perform the two-dimensional search. In addition, the proposed method has no constraints on whether the antenna component of the spaceborne SAR can move relative to the main body of the spaceborne SAR, because this article only uses the relative positional relation between the main body of the spaceborne SAR and the antenna component. Even if the antenna of the spaceborne SAR is fixed, it can still be assumed that the antenna of the spaceborne SAR reaches the  
Figure 13: The plane containing the scatterers of the parabolic antenna edge vs. the plane containing the estimated scatterers under the non-ideal look angle. actual attitude by rotating in the yaw and roll directions relative to the main body of the spaceborne SAR. Robustness Results and Analysis of the Algorithm for Minimizing the Dilhedral Angle between the Estimated Plane and Actual Plane  
Figures 16 and 17 show the estimation error distributions of 100 Monte Carlo experiments using the experimental arc segments of LowEleArc and HighEleArc to estimate the look angle of the antenna when the spaceborne SAR is operating in boresight stripmap mode, respectively. Whether the LowEleArc experimental arc segment or the HighEleArc experimental arc segment is used, the estimation accuracy of the look angle increases with the increase in the SNR. In addition, the estimation accuracy using the HighEleArc arc segment is higher than that using the LowEleArc arc segment. Table 5 shows the statistical eigenvalues of the estimation errors of the antenna look angle of the spaceborne SAR operating in boresight stripmap mode obtained after 100 Monte Carlo experiments using the LowEleArc and HighEleArc experimental arc segments. The experimental results show that the method proposed in this article has high accuracy, good estimation performance, and high confidence in the estimation results.