In this paper, the scan mirror assembly for the space experiment Aerosol-UA scanning polarimeter (ScanPol) is described. The aim of the Ukrainian space mission Aerosol-UA is to create a database of the optical characteristics of aerosol and cloud particles in the Earth’s atmosphere over a long period of time. The optical characteristics of aerosol and cloud particles are derived from multiangular measurements. Multiangular scanning in ScanPol is provided by scan mirror assembly, which contains a reactive torque compensator electric motor and two scan mirrors, mounted on the shaft of the motor. The control system of the scan mirror assembly enables continuous scanning with a constant speed of the space under investigation. This control system tolerates movements of the orbiting satellite and preserves invariability of its spatial position. The polarimeter ScanPol is designed to acquire spatial, temporal, and spectral-polarimetric measurements simultaneously to minimize instrumental effects and “false” polarizations due to scene movement. Instrumental polarization, introduced by the mirrors of scan assembly, is minimized through the polarization compensated two-mirror scheme which contains two mirrors with orthogonal planes of incidence. In this paper, the polarimetric model of the polarization compensated two scan mirrors is considered. Theoretical calculations are given that substantiate the maximum allowable error of the relative angular position of the mirrors is 15 arcmin (0.25°), and the method of adjustment and control of the angular position of the mirrors is proposed. The polarization properties of mirrors are modelled in the spectral range of 370–1680 nm for bulk oxide-free aluminum. It is obtained that the maximum instrumental polarization of the unadjusted mirror system should be observed at 865 nm, and thus, the polarization characteristics of the scanning system at a given wavelength could be considered as representative for ScanPol in general. The key steps for assembling the unit are illustrated.

中文翻译：

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气溶胶-UA空间任务多光谱扫描旋光仪扫描镜组件

在本文中，描述了空间实验气溶胶-UA 扫描旋光仪（ScanPol）的扫描镜组件。乌克兰空间任务 Aerosol-UA 的目标是创建一个长期地球大气中气溶胶和云粒子光学特性的数据库。气溶胶和云粒子的光学特性来自多角度测量。ScanPol 中的多角度扫描由扫描镜组件提供，该组件包含一个无功扭矩补偿器电机和两个安装在电机轴上的扫描镜。扫描镜组件的控制系统能够以恒定速度对被调查空间进行连续扫描。该控制系统容许轨道卫星的运动并保持其空间位置的不变性。偏振计 ScanPol 旨在同时获取空间、时间和光谱偏振测量，以最大限度地减少仪器影响和由于场景移动引起的“错误”偏振。由扫描组件的反射镜引入的仪器偏振通过偏振补偿双反射镜方案被最小化，该方案包含两个具有正交入射平面的反射镜。在本文中，考虑了偏振补偿的两个扫描镜的偏振模型。给出了理论计算，证实了反射镜相对角位置的最大允许误差为15arcmin（0.25°），并提出了反射镜角位置的调节和控制方法。对于块状无氧化物铝，反射镜的偏振特性在 370-1680 nm 的光谱范围内建模。得出未经调整的反射镜系统的最大仪器偏振应在 865 nm 处观察到，因此，扫描系统在给定波长下的偏振特性通常可以被认为是 ScanPol 的代表。图示了组装单元的关键步骤。