# Estimating the Observation Area of a Stripmap SAR via an ISAR Image Sequence
## 4 Simulation Experiments
### Experimental Data Generation  
Due to the confidentiality of the measured data, simulation data were used to verify and analyze the proposed method. Therefore, first, the parameters for ISAR imaging the spaceborne SAR were set. The orbital elements of spaceborne SAR are shown in Table 1. The ground-based radar parameters were consistent with the Tracking and Imaging Radar (TIRA) space observation radar [28], and the detailed parameters are shown in Table 2. The 3D model of the spaceborne SAR is shown in Figure 6. The diameter of the parabolic antenna was 6 m and the focal ratio was 0.4. The radar station location parameters are shown in Table 3.  
Since the spaceborne SAR is a low-Earth satellite, its movement adopts a two-body orbit model. Considering the commonly used satellite attitude control methods, it is assumed that the main body of the spaceborne SAR is three-axis-stabilized and Earth-oriented. In addition, since the satellite's attitude control system has high precision [29; 30], the impact of the orbit attitude on the estimation accuracy of the proposed method can be ignored in this article. According to the satellite visibility method, within 24 h from the spaceborne SAR orbit epoch time, the ground-based radar observes a total of five visible arcs of the spaceborne SAR. The main information of the visible arcs is shown in Table 4. Without a loss of generality, the visible arc, Arc-1, with a low elevation angle, and the visible arc, Arc-3, with a high elevation angle, are selected as typical research representatives in this experiment; they are denoted as LowEleArc and HighEleArc, respectively.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Orbital Elements** & **Values** \\ \hline Semimajor axis & 6946.615 km \\ Eccentricity & 0.00048 \\ Inclination & 36.93\({}^{\circ}\) \\ Right ascension of ascending node & 334.87\({}^{\circ}\) \\ Argument of perigee & 63.81\({}^{\circ}\) \\ True anomaly & 296.05\({}^{\circ}\) \\ Epoch time & 22,191.71487269 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Orbital parameters of the spaceborne SAR.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Radar Parameters** & **Values** \\ \hline Waveform & LFM \\ Center frequency & 16.8 GHz \\ Bandwidth & 1 GHz \\ Pulse repetition frequency & 50 Hz \\ Sampling frequency & 1.5 GHz \\ Image resolution cells & 15 \(\times\) 15 cm \\ \hline \hline \end{tabular}
\end{table}
Table 2: Ground-based radar parameters.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Location Parameters** & **Values** \\ \hline Latitude & 41\({}^{\circ}\) N \\ Longitude & 86.8\({}^{\circ}\) E \\ Altitude & 0 km \\ \hline \hline \end{tabular}
\end{table}
Table 3: Radar station location.  
According to the ISAR imaging projection principle and the ISAR imaging model for spaceborne SAR, the 2D ISAR image sequence of the ISAR imaging the spaceborne SAR within the LowEleArc and HighEleArc can be generated as experimental observation data. As shown in Figure 8, the range and Doppler values of the scatterers on the parabolic antenna edge can be extracted from the ISAR image sequence to estimate the area observed by the spaceborne SAR operating in boresight stripmap mode.