# Thermal Optimization Design for a Small Flat-Panel Synthetic Aperture Radar Satellite
## 1 Introduction
To address the heat dissipation issue of the radiation detector for the ChubuSat-2, [PERSON] proposes high-thermal-conductive graphite sheets to be used as a flexible radiator fin for the radiation detector [20]. Graphite sheets have lighter weight and higher thermal conductivity than traditional fins. [PERSON] has designed an aluminum thermal storage panel for the battery of a small satellite using phase change materials (PCM). This design enables the storage and utilization of equipment heat between high- and low-temperature conditions in orbit, enhancing the temperature stability of the equipment and reducing the overall power consumption of the small satellite [21]. [PERSON] proposed that proper surface treatment of existing structures, such as the payload shell, can directly dissipate the heat from high-power components, thereby avoiding increased thermal coupling and more complex hardware stacking, ultimately contributing to reducing the size and weight of small satellites [22]. In addition, it is necessary to conduct reasonable tests to verify the correctness of the thermal design and the effectiveness of the onboard electronics [23; 24; 25]. This paper introduces a 310 kg high-resolution microwave remote sensing satellite equipped with an X-band SAR antenna, capable of achieving a maximum imaging resolution of 0.6 m. To ensure the normal operation and imaging quality of the satellite, some thin-film heaters are used for temperature control to ensure that the temperature of the antenna support plate is between 15 and 25 \({}^{\circ}\)C, and to ensure that the temperature of the T/RMs is not too low. To fulfill the design concept of reduced weight and lower power consumption, while ensuring the temperature stability of the SAR antenna [26], several strategies have been proposed, encompassing both the SAR antenna and the satellite platform. The SAR antenna is a microstrip phased array antenna, adopting a structure-thermalintegration design. The use of a high thermal conductivity structural substrate and a uniform component layout ensures the temperature consistency of the T/RM. This paper reasonably calculates the effective area of the TIM, controls the overall temperature level of the antenna, and ensures its operating temperature with zero-power consumption. The SAR antenna is connected to the satellite platform through a structural plate, which is called a support plate. To ensure that the temperature variation of the antenna support plate remains within 5 \({}^{\circ}\)C and to minimize the utilization of heaters, an optimized layout method for heaters has been proposed, and the maximum spacing for heater placement has been calculated. As the satellite is an initial version, some additional heat pipes are added to ensure its higher reliability, which is not necessary for the design of subsequent satellites. In the next generation SAR satellites, in order to achieve a longer imaging time, the fluid loops will be used to dissipate the heat of the working SAR antenna. Fluid loops have the ability to transport heat in large capacity over long distances. Moreover, when the antenna is not working, the fluid circuit could also transport the waste heat of the satellite platform to keep the antenna warm. This paper also elaborates on the thermal vacuum (TVAC) testing process of the SAR satellite. During the test, high-power emission of the satellite is achieved through an absorber box, which can be positioned within the vacuum chamber and possesses temperature control capabilities. This ensures the integrity of the satellite development process [27].