## 5 Experiments and Discussion  
### Micro-Vibration Test and Coupling Analysis  
To test the LOS jitters caused by multiple micro-vibration sources, a test platform with AQZSSDs was built in this paper, as shown in Figure 15a. The composition of the platform and the test process were described in Section 2, where the focal length and aperture of the collimator are 10 m and 600 mm, respectively. To prevent material creep and relaxation of the suspension ropes during long-term experiments, we conducted stress relaxation after installing the suspension system and fine-tuned the rope assembly based on the dynamometer readings before each experiment. In addition, another micro-vibration test platform with a rigid fixed gravity unloading tool is also built to test the micro-vibration, as shown in Figure 15b. The satellite platform carrying the optical payload is fixedly connected to the L-shaped fixed tooling through rigid legs. Before the test, the high-low point adjustment screw of the L-shaped tooling needs to be adjusted to ensure the light enters HPSOP parallelly. According to the micro-vibration measurement systems shown in Figure 15, the micro-vibration tests of the HPSOP, unloaded by a flexible suspension or a rigid fixed tool, respectively, were carried out in this paper. Similar to JWST's deep space exploration, there is a need to turn on the CMGs and cryocoolers at the same time when the HPSOP performs space steady-state observation missions. CMGs are used to maintain the attitude stability of space payloads, while cryocoolers are used to avoid the influence of temperature noise on high-precision imaging. (Note: the rotational speed of CMGs is 7000 r/min, while the cryocooler operates at a rotational speed of 15,000 r/min). The test results are shown in Figure 16. Note that the micro-vibration source consists of CMGs and cryocoolers. As shown in Figure 16, while the gravity unloading tool is in a rigidly fixed state, the image point movements of the HPSOP along the X-axis are equal to the Y-axis, and the peak frequencies of the LOS jitter are both 2.4 Hz, represented by \(F_{R2}\). When the gravity unloading tool is in a flexible suspension state, compared with the rigidly fixed state, the image point movements are significantly reduced along the Y-axis but without change on the X-axis. The reason is that while the suspension system avoids the high-frequency resonance of the fixed system, it introduces a new peak response at a lower frequency. Compared to the peaks that appeared in the fixed state, the new response peak reduced along the Y-axis but changed little along the X-axis, as shown in Figure 16b,c. In addition, for the flexible suspension state, the first peak frequencies of the LOS jitter along the X-axis and Y-axis are both 0.24 Hz, corresponding to \(F_{F1}\), and the second peak frequency \(F_{F2}\) appearing on the X-axis but not Y-axis is 0.39 Hz. Compared with the peak frequencies caused by the unloading tool in a rigidly fixed state, the peak frequencies appearing on the  
Figure 15: Micro-vibration test systems in different forms: (**a**) flexible suspension form of the AQZSSD; (**b**) rigid support form. flexible suspension state are close to 0 Hz, proving the quasi-zero stiffness of the AQZSSD. Notably, for the micro-vibration test of the HPSOP with AQZSSD, the LOS jitter angles about the X-axis and the Y-axis are 1.253 \(\upmu\)rad and 0.625 \(\upmu\)rad, respectively. Furthermore, as shown in Figure 17, for the collaborative operation of CMGs and cryocoolers, the LOS jitters may not equal the superposition of the micro-vibration caused by CMGs and cryocoolers independently. In this figure, \(J_{1}\) is the LOS jitter appearing when operating the CMGs, \(J_{2}\) is the LOS jitter of the cryocoolers, and \(\upalpha\) represents the coupling coefficient. Therefore, for guiding the improvement of the HPSOP's pointing accuracy, it is of great significance to evaluate the coupling micro-vibration between CMGs and cryocoolers.