Optimization design and implementation of eccentric tracking pendulum mirror for satellite-borne laser communication

Abstract

Currently, the construction of low-orbit satellite constellation is booming in the world. To make full use of carrier resources and improve launch efficiency, the extra-vehicular launch envelope size of spaceborne laser communication payload need to be smaller and flatter. Tracking mirror is the decisive factor of launch size because its rotating mechanism of external load and itself cannot be packed in to the cabin. . Therefore, we propose the design architecture of the tracking mirror with eccentric rotation axis and independent temperature control. the scanning space of the short side during the movement is reduced by tilting the rotation axis of the pendulum mirror to one side,. To decrease the height of the support axis for the pendulum mirror and minimize the overall launch envelope, the mirror is positioned horizontally during the launch stage. The design of the eccentric pendulum mirror utilizes rigid body isolation and radiation temperature control. It considers various factors including material properties, adhesive layers, and film layers. Additionally, it implements multi-point flexible installation and lens radiation temperature control techniques, while fine-tuning parameters through finite element analysis. The design achieved a 67.5mm reduction in the size of the transmitting envelope, accounting for 43% of the total height of the original mechanism. In the temperature range of 23~33℃, the RMS value of the pendulum mirror type changes to (1/166λ)/℃, which shows a linear trend. Lab test results show that the surface RMS value changes to (1/161λ)/℃ in the range of 21~32℃, which aligns wellwith the simulation value. The pendulum mirror has passed the mechanical and thermal vacuum environment test and achieved the design requirements, ensuring the smooth delivery of loads and on-orbit operation. Additionally, it introduces an innovative design optimization method for space eccentric tracking pendulum mirrors.