Thermal Control Design for Deep Space Optical Communication (DSOC) Docking Mechanism High-Output Paraffin Actuator

Deep Space Optical Communication (DSOC) is a technology demonstration laser communication payload riding on the Psyche spacecraft that will demonstrate data transmission via laser up to 2.76 AU (probe to sun). The payload achieves fine acquisition and tracking control by utilizing Lorentz force actuators to perform dual functions: mechanical isolation from the bus to provide a stable floating platform for the optical assembly, and to perform fine-grain pointing and tracking of the optical uplink receiver. To satisfy a Psyche requirement, during DSOC off periods, the floating platform is mechanically docked to the stationary side through the use of a pair of Docking Mechanisms (DMs). During an optical pass the optical platform has to be undocked by the DMs which each utilize a High-Output Paraffin (HOP) actuator to perform the undocking function. The DMs need to be in the undocked phase for up to 8 hours without any interruption or dithering of the HOP pin. Dithering has to be prevented because this could cause disruptions to the pointing of the optical assembly. Spacecraft bus voltage is also static so there inability of changing the power output to the HOP heater, which is critical due to strict paraffin temperature limits, thus, a pulse-width modulation (PWM) heating scheme was developed to achieve the desired power output. This PWM was then adapted and implemented in Psyche Flight Software (FSW). The flight unit DMs were tested successfully meeting all Verification & Validation requirements using this method for all temperature and voltage ranges. The DMs have been proven to work for 8+ hours in thermal vacuum, which is required for compliance of DSOC Project Level 1 requirements. This paper describes the development of the algorithm from inception to the final Psyche flight software implementation.

深空光通信（Deep Space Optical Communication, DSOC）是搭载于灵神星航天器的激光通信载荷技术演示项目，将验证通过激光实现的最远可达2.76天文单位（探测器至太阳的距离）的数据传输能力。该载荷通过洛伦兹力执行器实现双重功能，以此完成高精度捕获与跟踪控制：其一，与航天器平台实现机械隔离，为光学组件提供稳定的悬浮平台；其二，对光学上行链路接收器进行细粒度指向与跟踪。为满足灵神星任务的相关要求，在DSOC非工作时段，悬浮平台需通过一对对接机构（Docking Mechanisms, DMs）与静止侧完成机械对接。在光学通信通联时段，对接机构需解除悬浮平台的对接状态，每个对接机构均采用高输出石蜡（High-Output Paraffin, HOP）执行器完成解锁动作。对接机构需在解锁状态下持续最长8小时，且高输出石蜡执行器的插销不得出现任何抖动或偏移。必须避免此类抖动，否则可能干扰光学组件的指向精度。航天器平台的电压保持恒定，无法调整至高输出石蜡加热器的输出功率，而严格的石蜡温度限制对此至关重要，因此研究人员开发了脉冲宽度调制（Pulse-Width Modulation, PWM）加热方案以实现所需的功率输出。该脉冲宽度调制方案随后被适配并集成至灵神星飞行软件（Psyche Flight Software, FSW）中。采用该方案对飞行版对接机构开展了全温度与电压范围的测试，所有验证与确认（Verification & Validation, V&V）要求均顺利达标。对接机构已通过热真空环境下8小时以上的运行验证，满足DSOC项目一级合规要求。本文详述了该算法从初始构思到最终集成至灵神星飞行软件的完整开发历程。