(Innovation Academy for Microsatellites of CAS, Shanghai 201210)
先进天基太阳天文台(Advanced Space-based Solar Observatory, ASO-S)卫星姿控分系统的主要任务是实现高精度、高稳定度对日指向控制. ASO-S卫星的科学载荷中, 白光望远镜(White-light Solar Telescope, WST)前端配置了太阳导行镜(Guide Telescope, GT)稳像系统, 利用正交分布光电二极管组成的边缘探测器测量导行镜光轴与太阳中心的偏差角. 提出了一种将GT测量值引入姿态控制闭环的控制方法: 利用星敏陀螺定姿算法获得卫星-太阳方向姿态偏差, GT测量值确定非卫星-太阳方向姿态偏差; 以4斜装反作用轮组为执行机构, 进行三轴零动量稳定姿态控制. 通过数学仿真验证, 基于GT测量值的姿态控制器在非卫星-太阳方向的绝对指向精度优于$2'$、相对姿态稳定度优于$1'/60$s, 满足ASO-S卫星高精度高稳定度的对日指向要求.
An attitude control system is designed for Advanced Space-based Solar Observatory Satellite (ASO-S). The most important task of this attitude controller is to achieve high-precision and high-stability sun-pointing control. Among the scientific payloads aboard the ASO-S, there is an image stabilization system by using the guide telescope (GT) in front of the white-light solar telescope (WST). The GT can measure the deviation angle between the optical axis and the solar center by an edge detector composed of four orthogonal photodiodes. We propose a closed-loop attitude controller by using the GT measurements. The deviation angle along the satellite-sun direction is acquired through the attitude determination with star sensor and gyro, and the deviation angles along the vertical direction of satellite-sun vector can be obtained by the GT measurements. The attitude actuator is made up of four reaction wheels with zero angular momentum for the attitude stabilization controller. According to numerical calculations, the absolute pointing error along the vertical direction of satellite-sun is better than $2'$, and the relative pointing error is better than $1'$ in every 60 s by using the values of GT. This can satisfy the high-precision and high-stability requirements for the sun-pointing control.