## 4 Results
### Ground Verification Experiment  
In order to verify the feasibility of the OCPSI mode, we designed a ground verification device. Firstly, we choose a CMOS area array camera with a pixel size of 3.45 \(\times\) 3.45 \(\upmu\)m and the resolution of 1440 \(\times\) 1080, which can support the exposure time of 1 \(\upmu\)s\(\sim\)10 s and a lens with the focal length of 25 mm. Then, we use the sky rail to simulate the orbit and use three rotating mechanisms to simulate the orbital motion, the cone scanning motion, and the pendulum scanning motion. The experimental equipment is shown in Figures 24 and 25. \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Cone Scanning Angular** & **Pendulum Motion Angular** & **Exposure Time** & **Effective Width** \\  & **Velocity \(\omega_{s}\) (rad/s)** & **Velocity \(\omega_{c}\) (rad/s)** & \(t_{e}\) (\(\mu\)s)** & **(km)** \\ \hline Single-camera constant & 0.1831 & 1.8193 & 3.79 & 1060 \\ speed OCPSI mode & 0.0915 & 0.6317 (min) & 6.24 (min) & 966 \\ \hline  & & & & \\ speed OCPSI mode & 1.0670 (max) & 11.2 (max) & 966 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison table of related parameters of the two imaging modes. Figure 24: Experimental equipment: platform. We use the indoor pati as the experimental site for experiments, and the height of the experimental rail is 11 m. Due to the limited indoor space, we model it as \(\alpha=10^{\circ},\ N=3\). Since the sky rail is a soft rope with insufficient rigidity, the height of the platform will change during the operation of the platform, and the optical axis will also shift, as shown in Figure 26.  
We increased the overlap rate for improvement. We obtain the motion parameters of the OCPSI as the platform speed \(V_{s}\) is 0.04 m/s, the cone scanning speed \(\omega_{s}\) is 4.34\({}^{\circ}\)/s, and the pendulum motion speed \(\omega_{c}\) is 7.00\({}^{\circ}\)/s. Figure 27 is a simulation diagram of the ground experiment in the OCPSI mode, with the maximum width of 11.83 m.  
Figure 27: Simulation of ground experiment coverage in the OCPSI mode. Figure 25: Experimental equipment: load system. Image stitching is performed according to the collected images, and the experimental image is shown in Figure 28. The effective image is Figure 29, and the width reaches 10.80 m.  
Afterwards, we conducted push-broom and whisk-broom ground experiments with the same experimental equipment and experimental conditions. Figures 30 and 31 are experimental images. The width of the push-broom is 1.64 m, and a part of the overlap is required to ensure complete coverage. To achieve the width of the OCPSI mode, at least seven tracks are required. When the whisk-broom mode adopts the same whisk-broom half-cycle frame number as the OCPSI mode and the number of frames is three frames, the whisk-broom width is 3.83 m, and at least three tracks are required to achieve the width of the OCPSI mode. Figure 28: OCPSI mode: experimental image. Figure 30: Push-broom ground test cover diagram. Figure 31: Whisk-broom ground test cover diagram. Figure 29: OCPSI mode: effective image. However, compared to the push-broom mode and the whisk-broom mode, the OPCSI mode also has its limitations. The OPCSI mode has a larger roll angle (smaller entrance pupil brightness) and a smaller exposure time, so the OPCSI mode has a smaller SNR. This means that the image quality of OPCSI mode will be worse under the same conditions. In addition, due to the characteristics of in-motion imaging in OPCSI mode, the camera pendulum scanning velocity will be very fast. Compared with the push-broom mode and the whisk-broom mode, it will put forward higher requirements on the attitude control ability of the satellite platform. In this section, we first designed and simulated a single-camera constant speed OCPSI mode. The results showed that the effective swath of this mode was large, but the overlap area was also larger, and the exposure time was low.