###### Abstract  
The lightweight and displacement-stable design of the mechanical support structure within the APTS (Acquisition, Pointing, and Tracking System) is crucial for enhancing the payload capacity of remote sensing, satellite communication, and laser systems, while still meeting specified functional requirements. This paper adopts the Solid Isotropic Material with Penalization (SIMP) method to investigate the structural topology optimization of the L-shaped bracket in the APTS, aiming to minimize structural compliance while using volume, key point displacement, and maximum stress as constraints. In the optimization model, differences in the topology of the L-shaped bracket structure are explored to minimize structural compliance, which was performed under volume, key point displacement, and stress constraints, and the results are compared with the initial reinforced structure. The innovative L-shaped bracket structure obtained through topology optimization uses significantly less material than the initial reinforced design, while still meeting the displacement and stress constraints. After smoothing, rounding, and finite element analysis, the displacement and stress performance of the optimized L-shaped bracket structure satisfies the set constraints. The method proposed in this paper offers an innovative solution for the lightweight design of mechanical support structures in APTS, with significant engineering application potential. 2024 11 939 1  
A Article  
To appear in the Journal of the American Society of America, 2000. Thus, the traditional collimation frame in the APT system uses a gimbal-based structure for enhanced mechanical strength. As shown in Figure 1, to achieve a larger pitch angle, a typical gimbal-based collimation frame consists of a U-shaped or L-shaped frame, optical lens, pitch axis, azimuth axis, and pedestal. While the U-shaped frame offers better mechanical properties, it is heavier, significantly increasing the cost of satellite launches. This paper employs a hybrid method of topology optimization (TO) and a gradient-based optimization algorithm to optimize the L-shaped bracket and achieve a lightweight design for the APT system. Topological optimization of structures is an effective method for achieving innovative lightweight in aerospace equipment. Additive manufacturing offers greater potential for realizing models derived from structural topological optimization. The flexibility of additive manufacturing processes facilitates the implementation of topological optimization designs, offering broad prospects for aerospace applications. As shown in Figure 2, engineers from Altair, Airbus, and BAE Systems jointly used the OptiStruct 2024.1 software platform to perform topology, shape, and size optimization on the ribs of the Airbus A380 wing. This resulted in a 500 kg weight reduction for each A380 aircraft, significantly improving performance and reducing operating costs for airlines. Topology optimization is one of the most crucial approaches to lightweight structures. It provides designers with a conceptual design at the initial stage of engineering structural design, enabling the adoption of optimal layout solutions, which results in greater economic benefits compared to sectional optimization and shape optimization. It has become a hot topic in structural optimization design research today. It explores the interconnection of structural components, the topology forms such as the presence or absence of voids, and the number and position of voids, allowing structures to achieve optimal performance indicators under constraints such as balance, stress, displacement, and others [4; 5]. The pioneering work on topology optimization of continuum structures can be traced back to  
Figure 1: APTS system: (**a**) U-shaped frame. (**b**) L-shaped frame. Figure 2: Optimization design of the topology, shape, and dimensions of the A380 wing ribs. [PERSON] and [PERSON]'s [6] study on the minimum compliance of solid plates.