## 2 The Impact of Satellite Bus Thermal Deformation on the Laser Communication Load Acquisition Time  
In general, the energy of the laser beam has a significant impact on the transmission bandwidth of the laser communication load. The beam of the laser communication load is typically constructed at a smaller angle to improve the gain of the laser beam for communication [4]. In light of the relatively narrow laser beam, it is generally necessary to design a more complex acquisition, tracking, and pointing (ATP) system for laser communication loads because errors in attitude measurement accuracy, attitude pointing accuracy, orbit measurement error, and other aspects of communication satellites in orbit will make alignment of the laser difficult [12]. The reduction of the acquisition time of the laser communication payload in orbit has significant economic implications for satellite communication. The topological relationship between the relative positions of satellites will be impacted by the continually changing orbit characteristics, particularly for large communication satellite constellations, leading to repeated disconnection and reconnection of laser communication lines. One can only reduce, rather than completely eliminate, the time required for laser chain formation and reconnection. The effective communication duration can be increased by shortening each chain's building time, increasing the overall working efficiency of the communication satellite [10; 20]. Topology optimization can increase the effectiveness of link establishment over the entire constellation after the communication satellite has finished networking [21]. Reduced connection establishment times are crucial since this constellation's topology optimization method necessitates frequent link switching. The low-orbit communication test satellite 03/04's laser communication load installation directional thermal stability optimization design is the basis for this work. On 20 May 2022, the low-orbit communication test satellite 03/04 was launched. In Figure 1, one of the satellites is depicted. The two satellites were in a circular orbit with an eccentricity of zero, an inclination angle of 86 degrees, and an altitude of 880 km. In order to complete the laser communication task verification between two satellites in the same orbit as well as two satellites in a future adjacent orbit, an inter-satellite laser communication payload is configured in the flight direction and the flight opposite direction of the satellite, respectively. Figure 2 displays the schematic diagram of the laser communication chain. Low-orbit communication test satellite inter-satellite communication calls for link switching between the same orbit and the different orbit, as well as re-capitulation of the broken link. Reduced alignment intervals are important for the laser communication satellite. The laser communication load used in this project is shown in Figure 3. Its appearance is shown in Figure 3a. The surface is a thermal control coating material. Its composition and principles are shown in Figure 3b. The laser communication load consists of an optical telescope, a relay optical path transmitting system, a beacon transmitting optical system, and an electronic unit. The two-dimensional turntable of the optical telescope realizes the coarse pointing function of the laser communication load of the target satellite. The precise tracking is located in the relay optical path, and the piezoelectric fa  
Figure 1: Low-orbit communication test satellite. used as the actuator. Precision tracking control can realize the control function of higher frequency characteristics and the correction of small angle deviation, which is mainly used to reduce the influence of satellite high-frequency vibration sources such as flywheels and SADA on laser communication.